WaterSense

WaterSenseฎ Technical Evaluation Process for
Approving Home Certification Methods

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WaterSense

WaterSense* Technical Evaluation Process for
Approving Home Certification Methods

Table of Contents

1.0 Introduction and Purpose	1

2.0 Definitions	1

3.0 Summary of the Technical Evaluation Process	2

4.0 Technical Evaluation Details and Assumptions	3

4.1	Scope	4

4.2	Reference Home Designs	4

4.3	Evaluating Indoor Water Use	9

4.3.1	Establishing Occupancy	9

4.3.2	Establishing Water Use for Indoor Baseline and Water-Efficient
Configurations	10

4.3.2.1	Toilet Water Use	12

4.3.2.2	Shower Water Use	13

4.3.2.2.1 Savings From Thermostatic Shutoff Valves	14

4.3.2.3	Lavatory Faucet Water Use	15

4.3.2.4	Kitchen Faucet Water Use	17

4.3.2.5	Clothes Washer Water Use	19

4.3.2.6	Dishwasher Water Use	20

4.3.2.7	Bathtub Water Use	21

4.3.2.8	Water Waste From Hot Water Delivery	22

4.3.2.9	Water Waste From Household Leaks	24

4.4	Evaluating Outdoor Water Use	25

4.4.1	Establishing Outdoor Water Use for Baseline Configuration	29

4.4.2	Establishing Outdoor Water Use for Efficient Configuration	29

4.4.2.1	Option 1: Landscape Type and Irrigation Feature-Based
Approach	30

4.4.2.1.1	Savings From Pressure Regulation	31

4.4.2.1.2	Savings From Irrigation Scheduling Technologies....31

4.4.2.1.3	Savings From Professional Irrigation Design,
Installation or Audit	33

4.4.2.2	Option 2: Irrigation System Capacity Control	33

4.5	Other Water U ses	35

4.6	Generating Total Water Efficiency Percent Savings	36

5.0 EPA Response to HCOs	36

6.0 Amendments, Modifications and Revisions	36

7.0 More Information	37

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WaterSense* Technical Evaluation Process for
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WaterSense Technical Evaluation Process for Approving Home

Certification Methods

1.0 Introduction and Purpose

Under the WaterSense Specification for Homes, the U.S. Environmental Protection Agency
(EPA) requires homes that earn the WaterSense label to be at least 30 percent more water-
efficient than comparable homes with characteristics typical of new construction (i.e., meets
national standards and follows common design and landscape practices). To confirm adherence
to this requirement, homes must be certified under a Home Certification Organization's (HCO's)
WaterSense Approved Certification Method (WACM), as described in the WaterSense Home
Certification System. To become a WACM, WaterSense must confirm a proposed certification
method (PCM) is able to differentiate homes that meet WaterSense's efficiency requirement
from homes that do not.

This WaterSense Technical Evaluation Process for Approving Home Certification Methods
(Technical Evaluation) describes WaterSense's process for assessing PCMs. The purpose of
the evaluation is to provide reasonable assurance that in instances where the PCM's
requirements are met, water savings of at least 30 percent can be expected. Only PCMs that
are capable of consistently achieving WaterSense's required water efficiency criteria will be
approved by the WaterSense program, thus becoming a WACM. The technical evaluation
represents a protection of WaterSense's brand promise to only allow the WaterSense label to
be associated with homes that demonstrate significant, quantifiable water savings and
performance, as defined in the specification.

The purpose of this document is to explain EPA's process and assumptions used to evaluate
the water efficiency level achieved by a PCM. Section 2.0 defines terminology used throughout
the technical evaluation; Section 3.0 provides a brief overview of the technical evaluation
process; Section 4.0 provides the details of the technical evaluation process and assumptions;
and Section 5.0 discusses EPA's approval of PCMs that achieve at least 30 percent water
efficiency, as determined by the technical evaluation.

2.0 Definitions

Definitions within the WaterSense Home Certification System are included by reference. Two
definitions from the certification system are repeated here for convenience.

Proposed Certification Method (PCM): Methodology proposed by an HCO to evaluate a
home's compliance with the water efficiency requirement in the WaterSense Specification for
Homes. The PCM includes the technical requirements or criteria and the certification threshold
homes must meet to demonstrate adherence to the water efficiency requirement in the
WaterSense Specification for Homes.

WaterSense Approved Certification Method (WACM): A certification method that EPA has
evaluated in accordance with the certification method technical evaluation process and has
determined can effectively differentiate homes that meet the water efficiency requirement in the
WaterSense Specification for Homes. In addition to the Mandatory Checklist, the WACM serves
as the basis for certifying and labeling homes for the WaterSense program.

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Other definitions applicable to this technical evaluation document include:

Reference Home/Reference Building: Set of assumed physical attributes of a home (e.g., lot
size, number of bedrooms, number of bathrooms, minimum features installed) or multifamily
building (e.g., landscape area, number of units, minimum features installed) EPA uses as a
template for evaluating baseline water use and water efficiency gains across a range of homes
that could be certified under a PCM. As part of this technical evaluation, EPA uses four single-
family reference home and four multifamily reference building scenarios to represent a broad
range of physical attributes that are realistic in new construction. These reference homes and
buildings do not represent national or regional averages for these physical attributes. Instead
they allow EPA to assess whether the PCM is able to meet the WaterSense water efficiency
requirement across an array of physical home attributes.

Baseline Configuration: Term used to describe each reference home scenario that
incorporates water use characteristics typical of new construction. Estimated water use from a
home with characteristics typical of new construction assumes that the home is constructed to
applicable national standards (e.g., plumbing fixture flush volumes and flow rates), as well as
common design and landscape practices. These typical construction characteristics are applied
to the relevant reference homes and/or buildings to create the baseline in the water use
comparison. EPA's assumptions related to typical construction characteristics are discussed in
Section 4.3 and Section 4.4.

Water-Efficient Configuration: Term used to describe each reference home scenario that
incorporates features and assumptions that would be eligible for the WaterSense label under
the PCM. Characteristics as defined by the PCM are applied to the relevant reference homes
and/or buildings to create the water-efficient configuration used in the water use comparison.
For the purposes of the evaluation, EPA assesses the least-efficient (i.e. highest water use)
configuration that still meets the certification threshold for the specific PCM. EPA's assumptions
related to water efficiency characteristics are discussed in Section 4.3 and Section 4.4.

3.0 Summary of the Technical Evaluation Process

Proposed Certification Method Scope Identification

As described in the WaterSense Home Certification System, an HCO shall supply EPA with a
copy of its PCM and additional supporting documentation. The HCO's application to EPA must
indicate the PCM's building eligibility (single-family and/or multifamily, new and/or existing
construction) and geographic scope (i.e., national, regional, local). The HCO must also indicate
the certification threshold (e.g., number of points, certification level, rating) it intends to
designate for homes to earn the WaterSense label. EPA will use the HCO's stated scope to
perform its technical evaluation. EPA will only approve the HCO's WACM for use with the stated
building type and geographic region.

Determining "Least Efficient" Home and Landscape Design

Once the scope of the HCO's PCM is clearly defined, EPA will define one or more home and
landscape designs to evaluate based on the minimum requirements a home must meet to
achieve the PCM's stated certification threshold for WaterSense. EPA's goal is to determine the
home and landscape designs that potentially result in the "least efficient" homes that could earn

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the WaterSense label. The features of the "least efficient" home and landscape designs will be
incorporated into the assumptions and form the basis for the water-efficient home
configurations. The process is intended to help EPA assess the minimum savings that are likely
to be achieved by homes certified to the PCM.

The WaterSense Specification for Homes includes the Mandatory Checklist for WaterSense
Labeled Homes (see Section 2.1 and Appendix B of the WaterSense Specification for Homes)
that requires all homes that earn the WaterSense label to be equipped with WaterSense labeled
toilets, lavatory faucets, and showerheads and be free of leaks. Therefore, the least efficient
home design(s) that EPA evaluates will automatically include these features.

Water Savings, Technical Evaluation, and Approval

The technical evaluation will compare water use in a set of four predefined reference homes
and/or reference buildings, as described in Section 4.2. Water use in each reference home
and/or reference building will be compared between a baseline configuration with characteristics
typical of new construction and a water-efficient configuration with characteristics of the "least
efficient" home and landscape design expected to achieve certification under the PCM. Because
some PCMs may provide flexibility in how homes can be configured to meet the requirements,
EPA may define multiple "least efficient" home and landscape designs and repeat the technical
evaluation across the reference homes. Homes must be able to meet EPA's water efficiency
requirement across all reference home/reference building and "least efficient" home design
scenarios in order for EPA to approve the PCM.

Sections 4.3 and 4.4 describe the assumptions and calculations EPA will use to evaluate water
use from the baseline and water-efficient configurations. The features and water savings
estimates included in the water use evaluation are those for which EPA has identified studies,
research, or other data that suggest quantifiable water savings can be achieved from
implementation of that feature. Wherever possible, EPA utilized industry recognized studies,
such as the Water Research Foundation's Residential End Uses of Water, Version 2, to identify
water use, water savings, or usage patterns of different water-using fixtures, appliances, or
systems. Throughout, EPA's objective is to use the best available data and to evaluate a
home's potential water use across a realistic range of scenarios.

Unless specifically included in Sections 4.3 and 4.4, all other requirements or features included
in a PCM are not assessed for water savings in EPA's technical evaluation. This is not to
suggest that other requirements or features that could be included in a PCM do not have the
potential to provide water savings, energy savings, or other environmental benefit. The
WaterSense label is meant to recognize homes that are assured to achieve the water efficiency
requirement from the WaterSense Specification for Homes; therefore, features for which water
savings cannot yet be reliably quantified are omitted. However, if an HCO believes that water
use or savings from a requirement or feature of its PCM is not adequately accounted for, the
HCO can submit technical justification to EPA for consideration. See Section 4.5 for more
details.

4.0 Technical Evaluation Details and Assumptions

EPA's technical evaluation involves applying a series of calculations and assumptions to
estimate baseline water use for several reference home scenarios intended to reflect a range of

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home and lot sizes, as well as common features. Similarly, the technical evaluation applies a
series of calculations and assumptions to estimate water use associated with specific water
efficiency features based on the criteria for the water-efficient configuration(s) in the same
reference home scenarios. EPA will evaluate the water savings between the baseline and
water-efficient configuration(s) under each reference home scenario.

The outdoor water use and savings assumptions vary depending upon the geographic scope of
the PCM; therefore, EPA takes location into consideration when establishing the reference
homes. Section 4.1 discusses this geographic scope factor. Section 4.2 provides a detailed
explanation of the reference homes and Sections 4.3 and 4.4, respectively, describe the
assumptions and methods for calculating indoor and outdoor water use for the baseline and
water-efficient configurations of each reference home.

4.1	Scope

As identified in the Application for Home Certification Organization (HCO) and Proposed
Certification Method (PCM) Approval, a prospective HCO submits its PCM's building eligibility
(single-family and/or multifamily, new and/or existing construction) and geographic scope (i.e.,
national, regional, local) to EPA as part of its program application. EPA will evaluate the PCM
based on the specific scope identified by the HCO applicant.

Geographic scope impacts the reference home's anticipated outdoor water use since climate
has a well-documented impact on outdoor water use. For PCMs intended to certify homes at the
local level (i.e., within a specific city or county), EPA will use local zip codes to determine a
modified net evapotranspiration (NetET)1 with effective rainfall (ModNetET0, explained in more
detail in Section 4.4) to include in the technical evaluation. For PCMs to be used to certify
homes across a larger region, EPA will use a range of ModNetET0 values to represent the
geographic scope. For reference, values for ModNetET0 across the continental United States
range from approximately 20 inches per year to approximately 100 inches per year.2 For
national certification methods, EPA will use ModNetET0 values toward both ends of this range to
conduct the technical evaluation.

4.2	Reference Home Designs

EPA will analyze the expected differences in water use between a baseline and water-efficient
configuration in a series of reference homes with the same physical attributes (e.g., lot sizes,
number of bedrooms, number of bathrooms, minimum features installed). The series of basic
reference homes serves as a template for evaluating water efficiency gains associated with
homes that could be labeled under a PCM.

Both single- and multifamily homes can vary significantly in size and design. To avoid the need
to develop an overly complex procedure to normalize all possible variations of home size and
design, EPA has identified "reference home scenarios" that represent a broad range of typical
home physical attributes. These reference home scenarios are intended to ensure that

1	Evapotranspiration is a measurement of the amount of water a plant requires from optimal growth.

2	See Section 4.4 for information on how EPA calculates ModNetETo.

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WaterSense labeled homes will be able to meet EPA's water efficiency requirements across a
large range of likely home configurations that are possible under the PCM.

EPA identified features to include in the reference homes from the U.S. Department of Housing
and Urban Development (HUD) 2017 Survey of Construction. U.S. Census data were reviewed
to inform the range of typical design attributes—such as number of bedrooms, number of
bathrooms, and lot size—that were included in the reference homes.3 4

EPA established the landscape area for single-family reference homes based on a best fit
equation that was developed using observed field data from Residential End Uses of Water,
Version 2. Where the lot size of the reference home is less than 7,000 square feet (sq. ft.),
landscape area is calculated according to Equation 1. Where the lot size of the reference home
is greater than or equal to 7,000 sq. ft., the landscape area is calculated according to Equation
2.5

Equation 1: Landscape Area for Single-Family Reference Homes With Lot Size Less
Than 7,000 Square Feet

Landscape area = Lot size x (0.002479 x Lot size0,6157)

Equation 2: Landscape Area for Single-Family Reference Homes With Lot Size
Greater Than or Equal to 7,000 Square Feet

Landscape area = Lot size x 0.577

Landscape areas for the multifamily reference homes were established based on EPA's review
of multiple data sources including the Fannie Mae Multifamily Energy and Water Market
Research Survey6 and entries in ENERGY STARฎ Portfolio Managerฎ pertaining to EPA Water
Score. These data sources indicate that, while it is extremely common for multifamily buildings
to exhibit little to no outdoor water use, it is also observed that many properties have landscape
areas several times larger than their floor area. As a result, EPA set the landscaped area for
multifamily reference homes across a full range of values to capture all potential situations.

EPA assumes that an in-ground irrigation system is installed for each reference home. While
this does not necessarily represent characteristics typical of new construction in all regions,
EPA intends for the technical evaluation to assess homes with features likely to result in higher
water use. Available data strongly indicate that a home constructed without an in-ground

3	U.S. Census Bureau. Characteristics of New Single-Family Houses Completed.
www.census.aov/construction/chars/completed.html

4	U.S. Census Bureau. Characteristics of Units in New Multifamily Buildings Completed.
www.census.gov/construction/chars/mfu.html

5	American National Standards Institute (ANSI)/Residential Energy Services Network (RESNET)/lnternational Code
Council (ICC) 850-2020 Standard Calculation and Labeling of the Water Use Performance of One- and Two-Family
Dwellings Using the Water Rating Index.

6	Fannie Mae, 2012. Fannie Mae Multifamily Energy and Water Market Research Survey.
www.fanniemae.com/multifamilv/areen-initiative-market-research-survev

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irrigation system is likely to consume less water than a home with in-ground irrigation,7 and
therefore EPA is confident that a PCM that can effectively differentiate homes with in-ground
irrigation could also do so where an in-ground irrigation system is absent.

Table 4-1 summarizes the attributes of the single-family reference homes. Table 4-2
summarizes the attributes of the multifamily reference buildings.

Through the technical evaluation, EPA will evaluate each reference home/reference building
(that falls within the scope of the PCM) for baseline water use (both indoor and outdoor
combined), as well as anticipated water use and savings (indoor and outdoor combined) from
applying features of the water-efficient configurations(s) that could be certified under the PCM.
Sections 4.3 and 4.4 explain the calculations and assumptions used to conduct this evaluation
in more detail.

7 Water Research Foundation (WRF), 2016. Residential End Uses of Water, Version 2.

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Table 4-1. Single-Family Reference Homes

Attribute/
Feature

Single-Family
Reference Home
1:

Single-Family
Reference Home
2:

Single-Family
Reference Home
3:

Single-Family
Reference Home
4:

Small Footprint
and Large Lot

Small Footprint
and Small Lot

Large Footprint
and Large Lot

Large Footprint
and Small Lot

Bedrooms

2

2

5

5

Bathrooms

1.5

1.5

4

4

Footprint
(sq. ft.)

1,000

1,000

2,500

2,500

Number of
stories

1

1

2

2

Total square
footage (sq. ft.)

1,000

1,000

5,000

5,000

Lot size (sq. ft.)

22,000

4,440

22,000

4,440

Landscaped
area (sq. ft.)

12,694

1,938

12,694

1,938

Number of
toilets

2

2

4

4

Number of
showerheads

1

1

4

4

Number of
lavatory
faucets8

3

3

6

6

Number of
kitchen faucets

1

1

1

1

Number of
clothes washers

1

1

1

1

Number of
dishwashers

1

1

1

1

Irrigation
season9

Determined based
on climate data

Determined based
on climate data

Determined based
on climate data

Determined based
on climate data

8	The number of lavatory faucets exceeds the number of toilets based on EPA's assumption that dual vanities will be
installed in some of the home's bathrooms.

9	EPA uses a value for ModNetETo as an indicator of irrigation season. See Section 4.4 for more information.

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Table 4-2. Multifamily Reference Buildings

Attribute/
Feature

Multifamily
Reference Home
1:

Multifamily
Reference Home
2:

Multifamily
Reference Home
3:

Multifamily
Reference Home
4:

Small Building
and No Irrigated
Area

Small Building
With Irrigated
Area

Large Building
and No Irrigated
Area

Large Building
With Irrigated
Area

Units and
Bedrooms

20 units x 1
bedroom/unit = 20

20 units x 1
bedrooms/unit = 20

300 units x2.5
bedrooms/unit =
750

300 units x 2.5
bedrooms/unit =
750

Bathrooms

1 bathroom per unit

1 bathroom per unit

2 bathrooms per
unit

2 bathrooms per
unit

Landscaped
area
(sq. ft.)

None

40,000

None

600,000

Number of
toilets

20 units x
1 bathroom/unit =
20

20 units x
1 bathroom/unit=
20

300 units x
2 bathrooms/unit
= 600

300 units x
2 bathrooms/unit =
600

Number of
showerheads

20 units x
1 bathroom/unit =
20

20 units x
1 bathroom/unit =
20

300 units x
2 bathrooms/unit
= 600

300 units x
2 bathrooms/unit =
600

Number of
lavatory
faucets

20 units x
1 bathroom/unit =
20

20 units x
1 bathroom/unit =
20

300 units x
2 bathrooms/unit
= 600

300 units x
2 bathrooms/unit =
600

Number of
kitchen faucets

20 units x
1 kitchen/unit = 20

20 units x
1 kitchen/unit = 20

300 units x
1 kitchen/unit =
300

300 units x
1 kitchen/unit =
300

Number of
clothes
washers

20 units x
1 machine/unit = 20

20 units x
1 machine/unit = 20

300 units x
1 machine/unit =
300

300 units x
1 machine/unit =
300

Number of
dishwashers

20 units x
1 machine/unit = 20

20 units x
1 machine/unit = 20

300 units x
1 machine/unit =
300

300 units x
1 machine/unit =
300

Irrigation
season10

Determined based
on climate data

Determined based
on climate data

Determined
based on climate
data

Determined based
on climate data

10 EPA uses a value for ModNetETo as an indicator of irrigation season. See Section 4.4 for more information.

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4.3 Evaluating Indoor Water Use

Generally, indoor water use is heavily influenced by occupancy in addition to the efficiencies of
its technology and design features. Therefore, the technical evaluation estimates indoor water
use under each reference home scenario for a baseline configuration, with features and
efficiencies typical of new construction, and a water-efficient configuration, with features and
efficiencies based on the water-efficient home design(s) from the PCM.

The indoor water use reduction is considered with the outdoor water use reduction, discussed in
Section 4.4, to determine the total water savings for the home over the baseline, which must
meet EPA's water efficiency requirement across all reference home scenarios.

The subsections below describe how EPA estimates indoor water use within its technical
evaluation.

4.3.1 Establishing Occupancy

Indoor water use is largely influenced by home occupancy. Generally, the more occupants in a
home, the more water is used within the household, since most major end uses of water in
homes (e.g., toilet flushes, showers) rise proportionally with the number of occupants.

To maintain a focus on the physical home or building as opposed to future occupants, EPA uses
the number of bedrooms to predict occupancy. For the technical evaluation, EPA determines
occupancy based on Equation 3 and Equation 4, which were derived from the Residential
Energy Consumption Survey (RECS) and presented in the Florida Solar Energy Center's
Estimating Daily Domestic Hot-Water Use in North American HomesV

Equation 3: Single-Family Occupancy

Occupants = 1.09 + 0.54 x Number of bedrooms
Equation 4: Multifamily Occupancy

Occupants = (1.49 + 0.45 x Number of bedrooms per unit) x Number of units
Where:

•	Number of bedrooms is determined by the respective single-family and multifamily
reference homes discussed in Section 4.2.

•	Number of units is determined by the respective multifamily reference homes
discussed in Section 4.2.

11 Parker, Danny S. and Philip W. Fairey. Florida Solar Energy Center, 2015. Estimating Daily Domestic Hot-Water
Use in North American Homes. FSEC-PF-464-15. June 30, 2015. www.fsec.ucf.edu/en/publications/pdf/FSEC-PF-
464-15.pdf

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4.3.2 Establishing Water Use for Indoor Baseline and Water-Efficient
Configurations

The annual baseline indoor water use for each reference home is determined based on
Equation 5. The baseline water use is intended to represent the anticipated water use from a
home constructed using typical design practices and standard plumbing fixture, fitting, and
appliance efficiencies.

Equation 5: Annual Indoor Water Use for Baseline Configuration

Annual indoor water use for baseline configuration (gallons)

= [daily toilet use + daily shower use + daily lavatory faucet use
+ daily kitchen faucet use + daily clothes washer use
+ daily dishwasher use + daily bathtub use
+ daily structural water waste from hot water delivery
+ daily use from household leaks + other use (if applicable)]
x 365 days

Where:

•	Daily toilet use is established using Equation 7.

•	Daily shower use is established using Equation 8.

•	Daily lavatory faucet use is established using Equation 10.

•	Daily kitchen faucet use is established using Equation 12.

•	Daily clothes washer use is established using Equation 14.

•	Daily dishwasher use is established using Equation 15.

•	Daily bathtub use is established using Equation 16.

•	Daily structural water waste from hot water delivery is established using
Equation 17.

•	Daily use from household leaks is established based on Section 4.3.2.9.

•	Daily other use (if applicable) is determined based on information supplied by the
HCO and reviewed by EPA, as explained in Section 4.5.

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Annual indoor water use for each water-efficient reference home configuration is determined
based on Equation 6. This is intended to represent the anticipated water use from a water-
efficient home constructed using practices and efficiency measures adopted from the PCM.

Equation 6: Annual Indoor Water Use for Efficient Configuration

Annual indoor water use for efficient configuration (gallons)

= [daily toilet use + daily shower use

—	daily savings from thermostatic shutoff valves

+ daily lavatory faucet use + daily kitchen faucet use
+ daily clothes washer use + daily dishwasher use + daily bathtub use
+ daily structural water waste from hot water delivery

—	daily savings from hot water recirculation

+ daily use from household leaks + other use (if applicable)]
x 365 days

Where:

•	Daily toilet use is established using Equation 7.

•	Daily shower use is established using Equation 8.

•	Daily savings from thermostatic shutoff valves is established using Equation 9.

•	Daily lavatory faucet use is established using Equation 11.

•	Daily kitchen faucet use is established using Equation 13.

•	Daily clothes washer use is established using Equation 14.

•	Daily dishwasher use is established using Equation 15.

•	Daily bathtub use is established using Equation 16.

•	Daily structural water waste from hot water delivery is established using
Equation 18.

•	Daily savings from hot water recirculation is established using Equation 19.

•	Daily use from household leaks is established based on Section 4.3.2.9.

•	Daily other use (if applicable) is determined based on information supplied by the
HCO and reviewed by EPA, as explained in Section 4.5.

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4.3.2.1 Toilet Water Use

Toilet water use for each baseline and water-efficient configuration of a reference home is
determined based on Equation 7.

Equation 7: Daily Toilet Water Use

Daily toilet water use (gallons) = Occupants x Daily use x Toilet flush volume

Where:

•	"Occupants" is established using Equation 3 or Equation 4, depending on the
reference home.

•	Daily use = 5.0 flushes per person per day.12

•	Toilet flush volume (gallons per flush [gpf]) is dependent on whether the daily toilet
water use is being determined for the baseline or the water-efficient configuration.

o For baseline configurations, assume a toilet flush volume of 1.6 gpf. The
Energy Policy Act of 1992 (EPAct 1992) established this as the maximum
allowable flush volume for all gravity, flushometer-tank, and flushometer-
valve toilets.13

o For the water-efficient configurations, flush volume is determined based on
requirements or features included in the water-efficient home(s) under the
PCM; however, the flush volume cannot exceed 1.28 gpf. To earn the
WaterSense label, homes must meet the Mandatory Checklist, as
discussed in the WaterSense Specification for Homes, which requires all
toilets installed within a home to be WaterSense labeled. WaterSense
labeled tank-type and flushometer-valve toilets are required to have a flush
volume of 1.28 gpf or less.1415

12	Water Research Foundation (WRF), 2016. Residential End Uses of Water, Version 2. Table 6.7.

13	The maximum flush volume for toilets is codified in the Code of Federal Regulations (CFR) at 10 CFR Part 430.32.

14	EPA, 2014. WaterSense Specification for Tank-Type Toilets, Version 1.2. June 2, 2014.
www.epa.aov/sites/production/files/2017-01/documents/ws-products-spec-toilets.pdf

15	EPA, 2015. WaterSense Specification for Flushometer-Valve Water Closets, Version 1.0. December 17, 2015.
www.epa.aov/sites/production/files/2017-01/documents/ws-products-spec-fv-toilets.pdf

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4.3.2.2 Shower Water Use

Shower water use for each baseline and water-efficient configuration for a reference home is
determined based on Equation 8.

Equation 8: Daily Shower Water Use

Daily shower water use (gallons)

= Occupants x Daily use x Minutes per use
x Shower compartment flow rate

Where:

•	"Occupants" is established using Equation 3 or Equation 4, depending on the
reference home.

•	Daily use = 0.69 showers per person per day.16

•	Minutes per use = 7.8 minutes per shower.17

•	Shower compartment flow rate (gallons per minute [gpm]) is dependent on
whether the daily shower water use is being determined for the baseline or the
water-efficient configuration.

o For baseline configurations, a shower compartment flow rate of 2.5 gpm is
used, as EPAct 1992 established this as the maximum allowable flow rate
for all showerheads.18
o For the water-efficient configurations, the shower compartment flow rate(s)
is determined based on requirements or features included in the water-
efficient home(s) under the PCM; however, the flow rate cannot exceed 2.0
gpm per showerhead within a shower compartment. To earn the
WaterSense label, homes must meet the Mandatory Checklist, which
requires all showerheads installed within a home be WaterSense labeled.
WaterSense labeled showerheads are required to have a flow rate of 2.0
gpm or less.19

Multiple spray showers (individual shower compartments with either multiple showerheads,
supplemental body sprays, or supplemental hand wands) are frequently observed in homes and
can substantially increase shower water use. A PCM may fail to appropriately account for
multiple spray showers, specifically when incentive measures (i.e. points or credits) are
awarded on a per product basis or when calculations do not account for the full shower
compartment flow rate. In instances where this may be the case, WaterSense may increase the
estimated flow rate for one shower compartment of the water-efficient configuration (by up to 2.0
gpm) to recognize this practice and ensure it does not result in erroneous home certification. In
its technical evaluation, EPA will not increase the flow rate input if a PCM has measures in
place to limit the total flow rate of all devices. EPA will not assume an increased flow rate for the

16	WRF, 2016. Residential End Uses of Water, Version 2. Table 6.9.

17	WRF, 2016. Residential End Uses of Water, Version 2. Table 6.9.

18	The maximum water use (i.e., flow rate) for showerheads is codified in 10 CFR Part 430.32.

19	EPA, 2018. WaterSense Specification for Showerheads, Version 1.1. July 26, 2018.
www.epa.gov/sites/production/files/2018-07/documents/ws-products-specification-showerheads-v1-1.pdf

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shower compartment if the measures of the PCM are at least as stringent as the requirements
included in the Plumbing Manufacturers International (PMI) and Alliance for Water Efficiency
(AWE) Memorandum of Understanding (MOU), which requires the total combined flow rate from
all shower outlet devices controlled by one shower valve to not exceed 2.0 gpm. Where a
second shower valve is installed in a shower compartment designed for two persons in
residences, shower valves shall be installed not less than 96 inches apart, as measured
horizontally.20

While EPA recognizes the MOU between PMI and AWE as an important industry agreement
and has identified it as the preferred path to limit multiple spray showers, it is important to note
that it is recent (at the time of publication of this document). As a result, EPA will not apply this
penalty to PCMs for which stakeholder engagement has occurred prior to release of this
technical evaluation process document and have otherwise established some level of control for
the flow rate from multiple spray showers.

4.3.2.2.1 Savings From Thermostatic Shutoff Valves

There are two types of water waste associated with hot water distribution and use: structural
waste and behavioral waste. Structural waste, which is discussed further in Section 4.3.2.8,
represents the cooled-off hot water that often must be cleared from the hot water pipe that
connects the water heater to the plumbing fitting (e.g., showerhead, faucet) or other end use.
Behavioral waste constitutes water that has reached the desired temperature, but that runs
down the drain before the occupant uses the water (e.g., gets into the shower).21 Bathers could
walk away from the shower or tub while the water heats up, performing other tasks prior to
entering the shower. Any hot water that flows down the drain in the period after the water
arriving at the point of use is hot and before the user begins their activity is considered
behavioral waste.

Thermostatic shutoff valves (TSVs) can be used to eliminate behavioral waste from showering
events. TSVs shut off (or greatly reduce) the flow of water to the tub spout or showerhead when
water reaches a temperature hot enough for bathing. When the user is ready to enter the
shower, the TSV can be reopened to allow the flow of water.

For baseline configurations for each reference home, no water savings are applied for TSVs,
since these devices are not required by code and WaterSense does not have any information to
suggest these devices are typically installed in new construction. Water savings are applied only
if a PCM requires or credits for installation of TSVs and EPA has included it as part of the water-
efficient configuration(s). Water savings to be applied to the water-efficient configuration for
each reference home are determined using Equation 9.

20	Plumbing Manufacturers International and Alliance for Water Efficiency, 2019. Memorandum of Understanding.
November 7, 2019.

www.allianceforwaterefficiencv.orq/sites/vvww.allianceforwaterefficiencv.orq/files/assets/AWE PMI MOU Multi-
Showerhead Siqned.pdf

21	Lutz, Jim, 2011. Water and Energy Wasted During Residential Shower Events: Findings from a Pilot Field Study of
Hot Water Distribution Systems. Lawrence Berkeley National Laboratory. LBNL-5115E. September 2011.

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Equation 9: Daily Water Savings from TSVs for Efficient Configuration

Daily water savings from TSVs for efficient configuration (gallons)
= Occupants x Daily use x Volume saved per use

Where:

•	"Occupants" is established using Equation 3 or Equation 4, depending on the
reference home.

•	Daily use = 0.69 showers per person per day.22

•	Volume saved per use = 1.13 gallons per showering event.23

4.3.2.3 Lavatory Faucet Water Use

Daily lavatory (bathroom) faucet water use for the baseline configuration for each reference
home is determined based on Equation 10.

Equation 10: Daily Lavatory Faucet Water Use for Baseline Configuration

Daily lavatory faucet water use for baseline configuration (gallons)
= Occupants x Daily use x Gallons per use

Where:

•	"Occupants" is established using Equation 3 or Equation 4, depending on the
reference home.

•	Daily use = 5.7 lavatory faucet uses per person per day.24

•	Gallons per use = 0.5 gallons.25

Faucet flow rate cannot be directly used to estimate water use because of user behavior.
Frequently, a faucet is not turned entirely open during use, but is adjusted to meet the end
user's needs for hand washing, teeth brushing, or other behaviors. Residential End Uses of
Water, Version 2, found a volume per faucet use of 0.5 gallons. EPA uses this value, along with
expected uses per person per day, to establish water use for a baseline configuration.

To estimate lavatory faucet savings for the water-efficient configuration, EPA utilizes the same
information that was examined during the development of WaterSense's High-Efficiency
Lavatory Faucet Specification. EPA reviewed two retrofit studies prepared by Aquacraft Inc.,

22	WRF, 2016. Residential End Uses of Water, Version 2. Table 6.9.

23	Sherman, Troy, 2014. Disaggregating Residential Shower Warm-Up Waste: An Understanding and Quantification
of Behavioral Waste Based on Data from Lawrence Berkeley National Labs. August 11, 2014.

24	Because WRF's Residential End Uses of Water, Version 2 does not differentiate between lavatory faucet and
kitchen faucet uses, EPA assumes that the number of lavatory faucet uses per occupant per day is equal to the
number of toilet flushes per occupant (5.0) plus the number of showers per occupant (0.69), as determined by
Residential End Uses of Water, Version 2.

25	WRF, 2016. Residential End Uses of Water, Version 2. Table 6.10.

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one in Seattle, Washington in 2000,26 and one in the service area of East Bay Municipal Utility
District (EBMUD) in 2003,27 where 1.5 gpm aerators were installed in place of existing faucet
aerators. Post-faucet retrofit, the weighted average daily per capita reduction in water
consumption achieved was 0.6 gallons per capita per day (gcpd).28 For a lavatory faucet flow
rate below 1.5 gpm, EPA intends to extrapolate these savings linearly, so additional savings in
the technical evaluation are proportionally applied to a flow rate reduction beyond 1.5 gpm.
Therefore, the daily lavatory faucet water use for an efficient configuration is determined based
on Equation 11.

Equation 11: Daily Lavatory Faucet Water Use for Efficient Configuration

Daily lavatory faucet water use for efficient configuration (gallons) =

Baseline daily lavatory faucet water use — [Occupants x

(Standard lavatory faucet flow rate — Efficient lavatory faucet flow rate) x

, Post-retrofit savings
Retrofit flow rate reduction

Where:

•	Daily lavatory faucet water use for baseline configuration is established using
Equation 10.

•	"Occupants" is established using Equation 3 or Equation 4, depending on the
reference home.

•	Standard lavatory faucet flow rate = 2.2 gpm.29

•	Efficient lavatory faucet flow rate =1.5 gpm or less, as determined based on the
requirements or features of the water-efficient home(s) under the PCM.

•	Post-retrofit savings = 0.6 gallons per person per day.

•	Retrofit flow rate reduction = 0.7 gpm, based on faucet flow rate reduction from the
Seattle and EBMUD retrofit studies from 2.2 gpm to 1.5 gpm.

For the water-efficient configurations, the efficient lavatory faucet flow rate is determined based
on requirements or features included in the water-efficient home(s) under the PCM; however,
the flow rate cannot exceed 1.5 gpm. To earn the WaterSense label, homes must meet the
Mandatory Checklist, which requires all lavatory faucets installed within a home to be
WaterSense labeled. WaterSense labeled lavatory faucets are required to have a flow rate of
1.5 gpm or less.30

26	Mayer, Peter W., William B. DeOreo, and David M. Lewis. 2000. Seattle Home Water Conservation Study: The
Impacts of High-Efficiency Plumbing Fixture Retrofits in Single-Family Homes. December 2000.

27	Mayer, Peter W., William B. DeOreo, Erin Towler, and David M. Lewis, 2003. Residential indoor Water
Conservation Study: Evaluation of High-Efficiency Indoor Plumbing Fixture Retrofits in Single-Family Homes in the
East Bay Municipal Utility District Service Area. July 2003.

28	EPA, 2007a. WaterSense High-Efficiency Lavatory Faucet Specification Supporting Statement. October 1, 2007.
www.epa.gov/sites/production/files/2017-01/documents/ws-products-support-statement-faucets.pdf

29	The maximum water use (i.e., flow rate) for lavatory faucets is codified in 10 CFR Part 430.32.

30	EPA, 2007b. WaterSense High-Efficiency Lavatory Faucet Specification, Version 1.0. October 1, 2007.
www.epa.gov/sites/production/files/2017-01/documents/ws-products-spec-faucets.pdf

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4.3.2.4 Kitchen Faucet Water Use

Daily kitchen faucet water use for the baseline configuration for each reference home is
determined based on Equation 12.

Equation 12: Daily Kitchen Faucet Water Use for Baseline Configuration

Daily kitchen faucet water use for baseline configuration (gallons)
= Occupants x Daily use x Gallons per use

Where:

•	"Occupants" is established using Equation 3 or Equation 4, depending on the
reference home.

•	Daily use = 14.3 kitchen faucet uses per person per day.31

•	Gallons per use = 0.5 gallons.32

As with lavatory faucets, kitchen faucet flow rate cannot be directly used to estimate water use
because of user behavior. In addition, a kitchen faucet could only be turned entirely open for pot
filling or other volumetric-based needs. In this case, flow rate would have an impact on run time,
but not total water use.

For the water-efficient configurations, EPA estimates kitchen faucet savings based on a similar
methodology it uses for lavatory faucets in Section 4.3.2.3; however, the methodology is
modified to apply a ratio of kitchen faucet uses to lavatory faucets, accounting for increased
daily uses of kitchen faucets compared to lavatory faucets. EPA is using this method because it
is not aware of any field studies to suggest estimated daily, annual, or per capita water savings
from reducing the flow rate of kitchen faucets.

31	Because WRF's Residential End Uses of Water, Version 2 does not differentiate between lavatory faucet and
kitchen faucet uses, EPA assumes that the number of kitchen faucet uses per occupant per day is equal to the total
number of faucet uses per occupant (20) minus the number of lavatory faucet uses estimated from Section 4.3.2.3.
Information on total daily faucet uses was determined in Residential End Uses of Water, Version 2, Table 6.10.

32	WRF, 2016. Residential End Uses of Water, Version 2. Table 6.10.

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The daily kitchen faucet water use for an efficient configuration is determined based on
Equation 13.

Equation 13: Daily Kitchen Faucet Water Use for Efficient Configuration

Daily kitchen faucet water use for efficient configuration (gallons) =

Daily kitchen faucet water use for baseline configuration — [Occupants x

(Standard kitchen faucet flow rate — Efficient kitchen faucet flow rate) x

,Kitchen faucet daily use. , Post-retrofit savings

Lavatory faucet dail use Retrofit flow rate reduction

Where:

•	Daily kitchen faucet water use for the baseline configuration is established using
Equation 12.

•	"Occupants" is established using Equation 3 or Equation 4, depending on the
reference home.

•	Standard kitchen faucet flow rate = 2.2 gpm.33

•	Efficient kitchen faucet flow rate = 2.2 gpm or less, as determined based on the
requirements or features of the water-efficient home(s) under the PCM.

•	Kitchen faucet daily use = 14.3 uses per person per day.

•	Lavatory faucet daily use = 5.7 uses per person per day.

•	Post-retrofit savings = 0.6 gallons per person per day.34

•	Retrofit flow rate reduction = 0.7 gpm, based on faucet flow rate reduction from the
Seattle and EBMUD retrofit studies from 2.2 gpm to 1.5 gpm.

For the efficient configurations, unless a more efficient flow rate is required or credited under a
PCM, EPA defaults the kitchen faucet flow rate at 2.2 gpm (the national standard flow rate) and
assumes no water savings are achieved. WaterSense does not currently label kitchen faucets
but could in the future.

33	The maximum water use (i.e., flow rate) for kitchen faucets is codified in 10 CFR Part 430.32.

34	The post-retrofit savings are based on the per capita per day water savings from retrofitting lavatory faucets, as
explained in Section 4.3.2.3; however, EPA is not aware of comparable savings data specific to kitchen faucets.

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4.3.2.5 Clothes Washer Water Use

Clothes washer water use for each baseline and water-efficient configuration for a reference
home is determined based on Equation 14.

Equation 14: Daily Clothes Washer Water Use

Daily clothes washer water use (gallons)

= Occupants x Daily use x Clothes washer capacity
x Clothes washer integrated water factor

Where:

•	"Occupants" is established using Equation 3 or Equation 4, depending on the
reference home.

•	Daily use = 0.3 loads per person per day.35

•	Clothes washer capacity = 3.9 cubic feet.36

•	The clothes washer integrated water factor is dependent on whether the daily
clothes washer water use is being determined for the baseline or the water-
efficient configuration.

o For baseline configurations, EPA uses an integrated water factor of 6.5
gallons per cycle per cubic foot, based on the federal requirements for top-
loading clothes washers with a capacity of 1.6 cubic feet or greater, as
codified in 10 CFR ง430.32.
o For the water-efficient configurations, the clothes washer integrated water
factor is determined based on requirements or features included in the
water-efficient home(s) of the PCM. If the PCM requires or provides credit
for ENERGY STAR certified clothes washers, EPA uses an integrated
water factor of 4.3, as this is the ENERGY STAR requirement for top-
loading clothes washers with a capacity greater than 2.5 cubic feet.37

35	WRF, 2016. Residential End Uses of Water, Version 2. Table 6.14.

36	Based on the average capacity (cubic feet) of clothes washers from U.S. Department of Energy (DOE) Energy
Efficiency and Renewable Energy (EERE) Compliance Certification Database. Accessed March 6, 2019.

37	ENERGY STAR Clothes Washers Program Requirements, Version 8.0. Effective February 5, 2018.
www.eneravstar.gov/products/appliances/clothes washers/partners

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4.3.2.6 Dishwasher Water Use

Dishwasher water use for each baseline and water-efficient configuration for a reference home
is determined based on Equation 15.

Equation 15: Daily Dishwasher Water Use

Daily dishwasher water use (gallons)

= Occupants x Daily use x Dishwasher gallons per cycle

Where:

•	"Occupants" is established using Equation 3 or Equation 4, depending on the
reference home.

•	Daily use = 0.1 loads per person per day.38

•	Dishwasher gallons per cycle is dependent on whether the daily dishwasher water
use is being determined for the baseline or the water-efficient configuration.

o For baseline configurations, EPA uses 5.0 gallons per cycle, based on the

federal requirements for dishwashers codified in 10 CFR ง 430.32.
o For the water-efficient configurations, the dishwasher gallons per cycle are
determined based on requirements or features included in the water-
efficient home(s) under the PCM. If the PCM requires or provides credit for
ENERGY STAR certified dishwashers, EPA uses 3.5 gallons per cycle.39

38	WRF, 2016. Residential End Uses of Water, Version 2. Table 6.15.

39	ENERGY STAR Program Requirements for Residential Dishwashers, Version 6.0. Effective January 29, 2016.
www.eneravstar.aov/products/appliances/dishwashers/partners

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4.3.2.7 Bathtub Water Use

Bathtub water use for each baseline and water-efficient configuration for a reference home is
determined based on Equation 16.

Equation 16: Daily Bathtub Water Use

Daily bathtub water use (gallons) = Occupants x Daily use x Volume per bath
Where:

•	"Occupants" is established using Equation 3 or Equation 4, depending on the
reference home.

•	Daily use = 0.07 baths per person per day.40

•	Volume per bath = 20.2 gallons.41

Because bath consumption is a fixed, volumetric use, EPA uses Equation 16 and the associated
inputs to generate water use for the baseline and water-efficient configurations for each
reference home. Under the technical evaluation, there is not a means to reduce water use from
baths.

Although it may not be significant, water use from baths is accounted for, since it is a likely use
of water within a home. Therefore, to ensure WaterSense labeled homes are able to reduce
water use by the requisite amount based on the water efficiency requirement from the
WaterSense Specification for Homes, EPA must establish a realistic baseline against which to
compare water savings, even if it means accounting for uses for which there are not options to
achieve savings.

40	WRF, 2016. Residential End Uses of Water, Version 2. Table 6.17.

41	WRF, 2016. Residential End Uses of Water, Version 2. Table 6.17.

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4.3.2.8 Water Waste From Hot Water Delivery

In a home with characteristics of typical new construction, there is potential for significant water
waste while a user waits for hot water to reach the showerhead or faucet. By improving hot
water distribution system design or installing an on-demand hot water recirculation system, the
amount of water wasted while waiting for hot water can be substantially reduced.

EPA establishes water waste from hot water delivery for the baseline configuration for each
reference home based on Equation 17.

Equation 17: Daily Water Waste From Hot Water Delivery for Baseline Configuration

Daily water waste from hot water delivery for baseline configuration (gallons)
= Occupants x Daily useful hot water draws
x Standard volume wasted per hot water draw

Where:

•	"Occupants" is established using Equation 3 or Equation 4, depending on the
reference home.

•	Daily useful hot water draws = 1.22 useful hot water draws per person per

day.42'43

•	Standard volume wasted per hot water draw = 1.77 gallons.44

The technical evaluation can estimate water savings from two methods for reducing water waste
from hot water delivery: 1) efficient design that reduces the piping distance and/or diameter
between the hot water heater and the point of use, thus reducing the amount of water that
needs to be cleared from the system before hot water arrives; or 2) inclusion of a hot water
recirculation system. EPA assigns savings for the water-efficient configuration(s) based on the
hot water delivery requirements of the PCM from either approach, but not both.

42	A useful hot water draw is characterized as an instance where the user waits for hot water to reach the plumbing
fitting (e.g., showerhead) priorto performing a task (e.g., showering).

43	EPA estimates the number of useful hot water draws per person per day to be the number of showers per person
per day (0.69; based on WRF, 2016. Residential End Uses of Water, Version 2. Table 6.9) and the number of long
faucet draws per person per day (0.53, based on Lutz, James, 2005. Estimating Energy and Water Losses in
Residential Hot Water Distribution Systems).

44	Based on Lutz, James, 2005. Estimating Energy and Water Losses in Residential Hot Water Distribution Systems.
The study estimated household daily water waste at 6.35 gallons, with an average occupancy of 2.8 persons per
household and 1.28 faucet and shower draws per capita per day.

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To account for efficient design that reduces the piping distance and/or diameter between the hot
water heater and point-of-use, EPA establishes water waste from hot water delivery for the
water-efficient configurations for each reference home using Equation 18.

Equation 18: Daily Water Waste From Hot Water Delivery for Efficient Configuration

Daily water waste from hot water delivery for efficient configuration(gallons)
= Occupants x Daily useful hot water draws
x Efficient home volume wasted per hot water draw

•	"Occupants" is established using Equation 3 or Equation 4, depending on the
reference home.

•	Daily useful hot water draws = 1.22 useful hot water draws per person per

day.45'46

•	Efficient configuration volume wasted per hot water draw is determined based on
requirements or features included in the water-efficient home(s) under the PCM.
For example, if a program requires or provides credit for designing a hot water
delivery system such that the volume of water stored in the piping must be less
than 0.5 gallons, then 0.5 gallons would be used.

Alternatively, if a reduction in hot water delivery water waste is accounted for in a water-efficient
home(s) through installation of a hot water recirculation system, EPA applies water savings to
the water-efficient configurations for each reference home, as determined by Equation 19.

45	A useful hot water draw is characterized as an instance where the user will wait for hot water to reach the plumbing
fitting (e.g., showerhead) prior to performing a task (e.g., showering).

46	EPA estimates the number of useful hot water draws per person per day to be the number of showers per person
per day (0.69; based on WRF, 2016. Residential End Uses of Water, Version 2. Table 6.9) and the number of long
faucet draws per person per day (0.53, based on Lutz, James, 2005. Estimating Energy and Water Losses in
Residential Hot Water Distribution Systems).

Where:

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Equation 19: Savings From Hot Water Recirculation System for Efficient

Configuration

Daily water savings from hot water recirculation for efficient configuration (gallons)
= Occupants x (Daily faucet savings attributable to recirculation
+ Daily showerhead savings attributable to recirculation)

Where:

•	"Occupants" is established using Equation 3 or Equation 4, depending on the
reference home.

•	Daily faucet savings attributable to recirculation = 0.97 gallons per person per
day.47

•	Daily showerhead savings attributable to recirculation = 1.11 gallons per person
per day.48

Savings calculated in Equation 19 are subtracted from the overall indoor water use for the
water-efficient configuration for each reference home.

4.3.2.9 Water Waste From Household Leaks

Household water leaks are a reality in many homes, including those that are newly constructed.
According to Residential End Uses of Water, Version 2, only 5 percent of existing homes
included in the study were completely free of leaks during the data collection period.49 A similar
study completed in 2011 by Aquacraft that assessed the water use patterns of new homes
designed and constructed to be high-efficiency (considered to be roughly equivalent to homes
built to the WaterSense Specification for New Homes, Version 1.0) found a median daily leak
rate of 2.8 gallons of water across the study homes.50 Therefore, to properly account for all
anticipated water uses in a home, EPA is including water waste from leaks in its technical
evaluation of baseline and water-efficient configurations for each reference home.

For baseline configurations, EPA assumes that each reference home has a daily leak rate of 4.3
gallons of water, based on the median daily household leak volume identified in Residential End
Uses of Water, Version 2.51 In contrast to other information cited from Residential End Uses of
Water, Version 2, where the mean value is used, EPA uses the median daily household leak
volume. This is because some study homes had cases of extreme water leaks, therefore
contributing disproportionately to the average leak rate. Residential End Uses of Water, Version
2 noted that 80 percent of homes in the study had daily leak volumes of 20 gallons or less,
contributing to only 17 percent of the total leaked volume identified in the study. EPA is also
using a per household leak rate rather than a per capita leak rate. While most indoor water uses
are largely dependent on occupants and their daily behaviors (e.g., toilet flushes, showers),

47	WRF, 2016. Residential End Uses of Water, Version 2. Table 6.29.

48	WRF, 2016. Residential End Uses of Water, Version 2. Table 6.29.

49	WRF, 2016. Residential End Uses of Water, Version 2. Page 130.

50	DeOreo, William B, 2011. Analysis of Water Use in New Single-Family Homes.

51	Based on the median daily household leak volume identified in WRF, 2016. Residential End Uses of Water,
Version 2. Table 6.18.

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leaks are independent of occupancy. Therefore, the 4.3 gallons for household water leaks is
applied across the baseline configuration for all reference homes.

The Mandatory Checklist requires homes earning the WaterSense label to be free of leaks at all
fixtures, fittings, and appliances and throughout the plumbing system and irrigation system (if
applicable). Therefore, EPA has assurance that homes are leak-free at the time of final
completion and certification. While this process is intended to identify and correct for any leaks
before certification, it would be unrealistic to expect these actions will impact all subsequent
leaks. To account for this verification, EPA's technical evaluation assumes the amount of water
waste from leaks is reduced by 50 percent (2.15 gallons per day) for the water-efficient
configurations for all reference homes.

While the technical evaluation assumes the actions included in the Mandatory Checklist reduce
water waste from leaks by 50 percent, the remaining 50 percent (2.15 gallons per day) can be
influenced if a leak detection and/or flow sensing system is required or credited for in the water-
efficient home(s) under a PCM. Leak detection or flow-sensing systems are used to monitor
water flows and detect if a household leak is occurring. The system will then either alert the
homeowner or shut off the water until the issue is resolved.

EPA is aware that there are data needs associated with this new type of technology. It is difficult
to estimate daily or annual water savings from leak detection devices, because actual water
savings are dependent on instances where significant water leaks are prevented; however, EPA
wants to recognize the benefits of these technologies and encourage their use by accounting for
savings in its technical evaluation. As better data become available, the technical evaluation can
be updated to reflect the best available data.

4.4 Evaluating Outdoor Water Use

Generally, outdoor water use is influenced by climate, irrigated area, irrigation (type of
technology and irrigation schedule/maintenance), and landscape features (e.g., plant type). EPA
uses this information within its technical evaluation to establish outdoor water use for each
baseline and water-efficient configuration, using the results from each reference home scenario
to compare the reduction in outdoor water use from installing water-efficient features and
implementing water-efficient practices. The outdoor water use reduction is considered with the
indoor water use reduction discussed in Section 4.3 to determine the total water savings for the
home compared to the baseline, which must meet EPA's water efficiency requirement across all
reference home scenarios for each PCM-specific, water-efficient design evaluated.

EPA uses a theoretical irrigation requirement (TIR) method to determine landscape water use,
for both the baseline (Section 4.4.1) and water-efficient landscape scenarios (Section 4.4.2).
The TIR accounts for factors such as irrigated area, plant types, reference evapotranspiration
(ET0), and allowance for irrigation inefficiencies. TIR is meant to determine how much water is
required for optimum plant growth. This method is based, with modification, on Residential End
Uses of Water, Version 2.52 As acknowledged in Residential End Uses of Water, Version 2,

52 WRF, 2016. Residential End Uses of Water, Version 2. (Note: The methodology is based on the landscape
coefficient method described in the University of California Cooperative Extension's A Guide to Estimating Irrigation
Water Needs of Landscape Plantings in California, which itself was derived from standard water engineering
techniques such as the U. S. Department of Agriculture, SCS Technical Release 21 and the American Society of Civil
Engineers, Evapotranspiration and Irrigation Water Requirements.)

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these methods have been used for many years. Additionally, Residential End Uses of Water,
Version 2 reiterates that it is important to acknowledge that the TIR is a "theoretical number
designed to optimize plant growth by fully supplying all of the water requirements as if for a
commercial or agricultural operation." It is not a predictive value and should not be used as
such; however, EPA intends to use it as a starting point to evaluate potential reduction in water

The calculation employed in the technical evaluation uses Equation 2053 to determine the TIR:

Equation 20: Theoretical Irrigation Requirement

Where:

•	TIR = theoretical irrigation demand (gallons per year).

•	0.6233 = conversion factor for inches of ModNetET0 to gallons per square foot.

•	ModNetETo = Modified net ET0 based on effective rainfall (inches), explained in
more detail below.

•	n = number of irrigated zones in the landscape.

•	i = individual zone.

•	Ai = irrigated area of individual zone (sq. ft.).

•	Effi = irrigation efficiency allowance of individual zone (taken from Table 3-3).

•	Kspecies = species coefficient (taken from Table 3-3).

Key TIR inputs are further described in the subsections below. Sections 4.4.1 and 4.4.2
describe how TIR is applied to estimate outdoor water use for a baseline and water-efficient
configuration, respectively.

Modified Net ET0 Based on Effective Rainfall

The purpose of this calculation is to determine the theoretical amount of water a reference plant
needs in the form of irrigation. It is calculated using monthly ET0 and rainfall data. EPA uses
reference ET (ET0) and rainfall data from the World Water and Climate Atlas, a project of the
International Water Management Institute (IWMI).54 EPA processed data from 1961 to 1990 to
determine monthly ET0 and rainfall for each zip code in the United States. For additional
information on data processing, please visit the WaterSense Water Budget Data Finder
webpage55 for details on converting IWMI data into monthly values.

ET0 is the rate of evapotranspiration from an extensive surface of cool-season grass cover of
uniform height of 12 centimeters, actively growing, completely shading the ground, and not short

53	Note that this equation is a modified version of Equation 3 in Residential End Uses of Water, Version 2.

54	International Water Management Institute (IWMI). World Water & Climate Atlas.
www.iwmi.cqiar.orq/resources/world-water-and-climate-atlas/

55	WaterSense Water Budget Data Finder, www.epa.gov/watersense/water-budqet-data-finder

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of water.56 Theoretically, ET0 minus effective rainfall is the amount of supplemental water the
reference crop needs for optimum growth.

Annual modified NetET0 based on effective rainfall (ModNetET0) is calculated according to
Equation 21.

Equation 21: Annual Modified Net ET0 Based on Effective Rainfall

Where (Monthly ET0- Monthly effective rainfall) is greater than 0:

Where:

•	Only positive values of (Monthly ET0- Monthly effective rainfall) are used as an
indicator for the irrigation season.

•	ET0 = Reference ET0 (inches).

•	Monthly effective rainfall = 25 percent of rainfall for a given month (inches).

Equation 21 modifies rainfall to acknowledge that not all the rain that falls is available to the
plant. EPA determined the effective rainfall to be 25 percent of total rainfall as a conservative
estimate to prevent underestimating the TIR in parts of the country with sustained rainfall during
the growing season.57 Then, effective rainfall is subtracted from ET0. The months with positive
values are then summed to determine annual modified NetET0 based on effective rainfall.

Note that only months with positive values of ET0 minus effective rainfall are included in the
sum, as these months more likely correspond to the irrigation season. Theoretically, during
months where effective rainfall exceeds ET0, a household's landscape should not require
irrigation. Therefore, EPA assumes that irrigation is only applied in months where ET0 exceeds
the effective rainfall. Months with negative values of ET0 minus effective rainfall are assumed to
be zero.

Irrigation Efficiency Allowance and Species Coefficient

Both the efficiency of an irrigation system and plant water needs impact the theoretical amount
of water required by a landscape. In the technical evaluation, EPA uses the values included in

56	Food and Agriculture Organization (FAO). 1998. Crop evapotranspiration—Guidelines for computing crop water
requirements—FAO Irrigation and drainage paper 56; and ASCE, 1990. ASCE Manual and Reports on Engineering
Practice 70. American Society of Civil Engineering in Irrigation Association. 2005. Landscape Irrigation Scheduling
and Water Management.

57	The Irrigation Association's "Landscape Irrigation Scheduling and Water Management" (2005) states that effective
rainfall should not exceed 50 percent for planning purposes. EPA selected 25 percent to remain consistent with the
WaterSense Water Budget Approach (2014; www.epa.qov/sites/production/files/2017-01/documents/ws-homes-
water-budaet-approach.pdf). so as to not underestimate the amount of irrigation required.

Annual ModNetET0 = (Monthly ET0 — Monthly effective rainfall)

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Residential End Uses of Water, Version 2 in order to remain consistent with peer reviewed
literature. The values used are displayed in Table 4-3.

Table 4-3. Landscape Parameters58

Landscape type

Species
Coefficient

(Kspecies)

Irrigation Efficiency
Allowance (Effj)

Combined Factor

Entire lot

NA

NA

NA

Non-turf plants with
spray irrigation3

0.65

71%

0.92

Pool or fountain

1.25

100%

1.25

Cool season turf

0.8

71%

1.13

Warm season turf3

0.6

71%

0.85

Vegetable garden

0.8

71%

1.13

Xeriscapeb

0.3

90%

0.33

Non-turf plants with
microirrigation0

0.65

90%

0.72

Non-irrigated ground

0

0%

0

a EPA modified this row to clarify that the combination is for non-turf plants irrigated with spray irrigation.
b EPA is reserving these species coefficients for regions where these plant types are most viable. EPA is reserving
the species coefficient forxeriscape plants for regions in warm, arid climates; EPA is reserving the species coefficient
for warm season turf for regions in warm climates.

c EPA added this row to the table. This type of landscape (non-turf plants) watered with microirrigation is not included
in Residential End Uses of Water, Version 2. EPA incorporated this additional combination because it is a common
practice in irrigated landscapes. While Residential End Uses of Water, Version 2 includes xeriscape with an irrigation
efficiency allowance assumed to be equated with microirrigation (90 percent), EPA is reserving the species coefficient
associated with xeriscape plants for only those regions in warm, arid climates, and therefore needed a combination
representing other non-turf plants that are watered with microirrigation. EPA selected 0.65 as the species coefficient
and 90 percent as the irrigation efficient allowance to remain consistent with Residential End Uses of Water, Version
2.

The species coefficient allows the TIR to account for the different plant water requirements. For
example, some plants require consistent irrigation, resulting in a higher species coefficient,
while others can exist on little, if any, irrigation.59 These values were developed as a percentage
of ET0. Additional information on how the species coefficients were determined is included in
Residential End Uses of Water, Version 2.

Irrigation efficiency allowance allows the TIR to account for inefficiencies in irrigation systems
and the fact that not all water that is distributed from the system is usable by plants, as some is
lost to evaporation, wind or overspray. The irrigation efficiency allowances included in
Residential End Uses of Water, Version 2 are based on well-designed irrigation systems, not
those typically found in the field. Spray irrigation is typically the lowest efficiency form of
irrigation (assigned 71 percent in Residential End Uses of Water, Version 2), due to factors such
as evaporation and runoff, whereas microirrigation is typically more efficient (assigned 90
percent in Residential End Uses of Water, Version 2) due to slower water delivery that is

58	Modified from WRF, 2016. Residential End Uses of Water, Version 2. Table 2.1.

59	WRF, 2016. Residential End Uses of Water, Version 2.

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targeted to plants' roots. Residential End Uses of Water, Version 2 assigned each ground cover
an irrigation efficiency based on whether it was expected to have spray or microirrigation.
Additional information regarding how these values were determined is included in Residential
End Uses of Water, Version 2. As explained in the footnotes of Table 4-3, EPA created an
additional combined value to account for a common combination of plant type and irrigation type
found in many water-efficient homes programs (i.e., non-turf plants watered with microirrigation).

4.4.1 Establishing Outdoor Water Use for Baseline Configuration

Baseline outdoor water use is determined for each reference home using Equation 22:

Equation 22: Annual Outdoor Water Use for Baseline Configuration

Annual outdoor water use for baseline configuration (gallons)

= Baseline TIR x Actual irrigation factor

Where:

•	Baseline TIR = theoretical irrigation requirement for the baseline scenario (assume
100 percent cool season turfgrass watered with spray irrigation) (gallons per year).

•	Actual irrigation factor = 0.58.60

For the baseline outdoor water use estimate, EPA assumes the entire landscaped area, as
determined according to Section 4.2, is comprised of cool season turfgrass irrigated with spray
irrigation. This assumption allows EPA to account for the highest likely water use. As described
in Section 4.1, EPA uses a specific, or range of, ModNetET0(s) within the TIR equation to
account for the geographic area and the climate where the reference home(s) are located.

EPA acknowledges that homeowners do not typically irrigate landscapes to their full water plant
demand. Therefore, EPA applies a factor of 58 percent to the baseline TIR to account for actual
anticipated irrigation. This factor is based on results generated in Residential End Uses of
Water, Version 2, which indicated that, on average, homeowners watered landscapes to 58
percent of their TIR.

4.4.2 Establishing Outdoor Water Use for Efficient Configuration

There are several different approaches that PCMs could implement to encourage water savings
outdoors. In general, these approaches fall into two categories: 1) an approach based on
landscape type and irrigation features (i.e., requiring or rewarding for more efficient plant
choices and/or irrigation systems, and/or promoting other water-efficient practices associated
with outdoor water use); and 2) an approach that promotes irrigation system capacity control
(i.e., limiting irrigation system flow rate and/or irrigated area).

60 Based on WRF, 2016. Residential End Uses of Water, Version 2. Page 157. Average actual water use by residents
in the study was 58 percent of their TIR.

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The technical evaluation can assess both approaches. EPA will select Option 1 or Option 2,
explained in more detail below, to evaluate the water-efficient configurations' outdoor water use
based on the PCM's outdoor requirements.

4.4.2.1 Option 1: Landscape Type and Irrigation Feature-Based Approach

Several home certification programs in the marketplace aim to impact outdoor water use by
influencing decisions made about landscape and/or irrigation features. There are two common
approaches that intend to reach the same goal. The first is a water budget, which aims to
influence design decisions about plant type (e.g., turf or shrubs/ornamentals) and irrigation type
(e.g., spray irrigation or microirrigation). The budget is typically developed using landscape area
and climate data (ET0 and rainfall), as well as plant type and irrigation type. The second
approach is a more prescriptive approach that either limits plants that typically consume more
water, limits certain types of irrigation, and/or rewards efficient design practices, such as
hydrozoning or head-to-head coverage for spray irrigation. Option 1 of the technical evaluation
is designed to determine outdoor water savings for PCMs that either implement the water
budget or use a prescriptive approach to encourage reductions in outdoor water use.

The following steps and calculations establish the outdoor water use for water-efficient
configurations using the landscape and irrigation feature-based approach. For purposes of this
next section, the TIR for water-efficient configurations will be indicated as Tl Reff to differentiate it
from the baseline TIR.

•	Step 1: Calculate the TlReff, using Equation 20, based on the plant types and
irrigation type for the water-efficient landscape design(s) included in a PCM (see
Section 4.2 for information on determining the water-efficient landscape design
for the reference home).

A Tl Reff is calculated for each zone and summed to calculate the Tl Reff for the total landscaped
area for each reference home.

•	Step 2: Calculate the outdoor water use for the water-efficient landscape design
for each reference home using Equation 23.

Equation 23: Annual Outdoor Water Use for Water-Efficient Landscape Design

Annual outdoor water use for efficient configuration (gallons)

= TIRejy x Actual irrigation factor

Where:

•	TIReff = theoretical irrigation requirement for the water-efficient landscape design
(gallons per year).

•	Actual irrigation factor = 0.58.61

61 Based on WRF, 2016. Residential End Uses of Water, Version 2. Page 157. Average actual water use by residents
in the study was 58 percent of their TIR.

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• Step 3: Subtract water savings associated with efficient irrigation technologies
and efficient practices from the outdoor water use for the water-efficient
landscape design (from Equation 23), which is based on the technologies
included in the water-efficient landscape design(s) included for the PCM.

In addition to placing requirements on plant type and irrigation type to achieve savings, many
PCMs require or provide credit for efficient irrigation technologies and/or practices. The
technical evaluation includes these requirements or credits by subtracting potential water
savings for each technology or practice included in the water-efficient configurations from the
outdoor water use for the water-efficient landscape design.

Technologies and practices for which additional savings are accounted for in the technical
evaluation are discussed in in the subsections below. Throughout the technical evaluation, EPA
considered technologies and practices with proven, quantifiable water savings.

4.4.2.1.1	Savings From Pressure Regulation

Landscape irrigation sprinklers are often installed at sites where the system pressure is higher
than what is recommended for the sprinkler nozzle. This can lead to excessive flow rates,
misting, fogging, and uneven coverage, all of which results in inefficient irrigation and water
waste. In irrigation systems, pressure can either be regulated at the valve or at the sprinkler
body, providing a consistent flow rate at the sprinkler nozzle. Additionally, when a sprinkler is
operating at its optimal pressure, the nozzle is better able to generate the right amount of water
spray and coverage for more uniform distribution of water across the landscape. For PCMs that
require or credit for installation of pressure-regulating valves or WaterSense labeled spray
sprinkler bodies62 in the water-efficient configuration(s), EPA applies 22 percent water savings
to the outdoor water use for the water-efficient landscape design (from Equation 23). The water
savings estimate of 22 percent is based on the reduction in flow calculated in the WaterSense
Specification for Spray Sprinkler Bodies Supporting Statement.63 In either case, the water
savings only apply to areas irrigated with spray irrigation, as the 22 percent savings identified by
EPA only applies to spray sprinklers. Savings are not applied to areas irrigated with
microirrigation, since pressure regulation for microirrigation/drip irrigation systems is typical
practice.

4.4.2.1.2	Savings From Irrigation Scheduling Technologies

The most common method used to schedule irrigation is a manually programmed clock timer
that irrigates for a specified amount of time on a preset schedule the user programs. In these
systems, the responsibility of changing the irrigation schedule to meet landscape water needs
lies with the end user or a contracted irrigation professional. Clock timer controllers can be a
significant source of wasted water because irrigation schedules are often set to water at the
height of the growing season, and the homeowner is unlikely to adjust the schedule to reflect
seasonal changes or changes in plant watering needs. For example, plant water requirements
decrease in the fall, but many homeowners forget to adjust their irrigation schedules to reflect
this change. Therefore, a homeowner could be watering in October as if it were July. As an

62	Spray sprinkler bodies that have earned the WaterSense label are required to have integral pressure regulation.

63	EPA, 2017. WaterSense Specification for Spray Sprinkler Bodies Supporting Statement. September 21, 2017.
www.epa.aov/sites/production/files/2017-09/documents/ws-products-support-statement-ssb.pdf

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alternative to a clock timer controller, "smart" scheduling technology, such as weather-based
irrigation controllers and soil moisture-based irrigation controllers (also known as soil moisture
sensors), can make irrigation schedule adjustments automatically by tailoring the amount,
frequency, and timing of irrigation events based on landscape conditions and either current
weather data or soil moisture levels. To a lesser extent, rainfall shutoff devices (also known as
rain sensors) can also provide a level of savings by interrupting the irrigation schedule during
periods of rain.

Within the technical evaluation, for PCMs that require or provide credit for one or more of these
technologies, EPA subtracts applicable water savings from the outdoor water use for the water-
efficient landscape design (from Equation 23, after savings from pressure regulation are
subtracted, if applicable), as follows:

•	Soil moisture-based irrigation controllers make irrigation schedule adjustments by
automatically tailoring the amount and/or frequency and timing of irrigation events based
on the moisture content of the soil in the landscape. The technical evaluation applies 30
percent water savings to the outdoor water use for the water-efficient landscape design
(from Equation 23) if soil moisture-based irrigation controllers are required or provided
credit for in a PCM. The savings value of 30 percent is based on the water savings
estimates included in the WaterSense Specification for Soil Moisture-Based Irrigation
Controllers Supporting Statement,64

•	WaterSense labeled weather-based irrigation controllers create or modify irrigation
schedules based on landscape attributes and real-time weather data, applying water
only when the landscape needs it. The technical evaluation applies 15 percent water
savings to the outdoor water use for the water-efficient landscape design (from Equation
23) if WaterSense labeled weather-based irrigation controllers are required or provided
credit for in a PCM. The savings value of 15 percent is based on the water savings
estimates calculated in the WaterSense Specification for Weather-Based Irrigation
Controllers Supporting Statement.65,66

•	Rain shutoff devices are products designed to interrupt a scheduled irrigation event
when a certain amount of rain has fallen. The technical evaluation applies a 6.7 percent
water savings to the outdoor water use for the water-efficient landscape design (from
Equation 23) if rainfall shut devices are required or provided credit for in a PCM. The
savings value of 6.7 percent is based on the water savings estimates included in the
Landscape Irrigation Controllers document developed by the Codes and Standards
Enhancement (CASE) Initiative in California.67

Each of these technologies functionally accomplish the same thing—using some indicator of
weather conditions (i.e., local weather data, soil moisture, rain) to alter the irrigation schedule.
Therefore, savings from these technologies are not additive. Thus, for PCMs that require or

64	EPA, 2021. WaterSense Specification for Soil Moisture-Based Irrigation Controllers Supporting Statement.

February 2021. www.epa.aov/watersense/soil-moisture-based-control-technoloaies

65	EPA, 2011. WaterSense Specification for Weather-Based Irrigation Controllers Supporting Statement. November 3,
2011. www.epa.qov/sites/production/files/2017-01/documents/ws-products-support-statement-irriqation-
controllers.pdf

66	Note that 15 percent water savings is based on data that WaterSense collected as part of the specification
development process for weather-based irrigation controllers prior to 2011. This estimate was later supported by
research conducted by Lawrence Berkeley National Laboratory (LBNL, 2014).

67	Codes and Standards Enhancement (CASE) Initiative, 2017. Landscape Irritation Controllers. September 18, 2017.

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provide credit for more than one of these technologies in the water-efficient home(s), only the
greatest water savings will be applied to the water-efficient configurations. For example, if a
PCM requires or provides credit for installation of a rainfall shutoff device and a WaterSense
labeled weather-based irrigation controller, the technical evaluation will only apply a water
savings of 15 percent to the outdoor water use for the water-efficient landscape design (from
Equation 23).

4.4.2.1.3 Savings From Professional Irrigation Design, Installation or Audit

As much as half of water used outdoors is wasted due to evaporation, wind, or runoff, often
caused by improper irrigation system design, installation, maintenance, or scheduling. Proper
commissioning of a system through efficient design, correct installation, and/or an audit done by
an irrigation professional can all reduce water wasted in an irrigation system. EPA provides
water savings within its technical evaluation to PCMs that require or provide credit for an
irrigation system that is designed, installed, and/or audited by an irrigation professional certified
by a WaterSense labeled program. These certified professionals are familiar with WaterSense
and the best practices for designing, installing, or maintaining an irrigation system.68 EPA based
the inclusion of professionally designed, installed, and/or audited systems on a research project
based in Colorado that examined pre/post audit usage of more than 2,000 participants. While
the study has limitations, results suggest that irrigation audits can save approximately 5
percent.69 EPA conservatively assumes that savings from professional irrigation design and
installation are commensurate. Therefore, in instances where the PCM requires a professional
irrigation design, installation, and/or audit, water savings of 5 percent is applied within EPA's
technical evaluation to the outdoor water use for the water-efficient landscape design (from
Equation 23, after savings from pressure regulation and irrigation scheduling technologies are
applied).

4.4.2.2 Option 2: Irrigation System Capacity Control

Research suggests that irrigation system flow rate and irrigated area significantly impact
outdoor water use, and can be used as a method to reduce outdoor water use in place of
prescriptive or water budget approaches that focus of specific plant types or irrigation
equipment.70 Therefore, some PCMs may be designed to influence outdoor water use by
limiting capacity (i.e., irrigation flow rates and irrigated area) instead of implementing a water
budget or more prescriptive approach.

The following calculations establish the outdoor water use for water-efficient configurations in
certification methods using the capacity control approach:

• Step 1: Apply capacity adjustment to the baseline configuration's annual outdoor
water use (from Equation 22).

68	For more information, visit the WaterSense Irrigation Professionals webpage: www.epa.gov/watersense/irriqation-
pro

69	The Center for Resource Conservation. 2014. Water Conservation Impact Assessment 2013 Final Report.

70	Sovocool, Kent, 2018. Estimating Annual Water Demands from Irrigation Flow Rates. Southern Nevada Water
Authority (SNWA).

www.irriqation.orq/IA/FileUploads/IA/Resources/TechnicalPapers/2018/Estimatinq Annual Water Demands SOVO
COOL.pdf

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Irrigation capacity can be determined by calculating a Residential Irrigation Capacity Index
(RICI) score, as described in Estimating Annual Water Demands from Irrigation Flow Rates,
prepared by Kent Sovocool from the Southern Nevada Water Authority (SNWA). A RICI score is
based on the flow rate for each irrigation valve and the corresponding irrigated area. In the most
basic sense, RICI demonstrates that higher water use is associated with the higher capacity of
the irrigation system (e.g., higher flow rates and larger areas result in higher outdoor water use).

RICI is calculated in Equation 24.

Equation 24: Residential Irrigation Capacity Index

Where:

•	Sum of flows for all irrigation valves (gpm).

•	Irrigation area (sq. ft.).

As part of the research study, during the standard development process for ANSI/RESNET/ICC
850-2020 Standard Calculation and Labeling of the Water Use Performance of One- and Two-
Family Dwellings Using the Water Rating Index, the author evaluated data from Residential End
Uses of Water, Version 2 and established a baseline RICI of 5. During this evaluation, the
author also determined that a 20 percent reduction in irrigation system flow rate (equivalent to a
RICI score reduction of 1) resulted in outdoor water savings of approximately 10 percent.71
Therefore, to determine outdoor water use for a water-efficient configuration, EPA applies 10
percent water savings to the baseline outdoor water use for every RICI score reduction of 1.

If a PCM requires or provides credits for capacity reduction, EPA will convert capacity reduction
to an applicable RICI score using Equation 24. EPA will then use Equation 25 to calculate the
outdoor water use for the water-efficient configurations considering the certification method's
reduction in RICI.

RICI =

Sum of flows for all irrigation valves

x 1,000

Irrigation area

71 Ibid.

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Equation 25: Annual Outdoor Water Use for Efficient Configuration Based on
Capacity Adjustment

Annual outdoor water use for efficient configuration (gallons)

= Annual outdoor water use for baseline configuration
— [Annual outdoor water use for baseline configuration
x (RICIBaseiine - RICIEff) x 10 percent]

Where:

•	Annual outdoor water use for baseline configuration is calculated based on Equation
22.

•	RICI Baseline — 5.

•	RICIEff is the RICI score of the water-efficient configuration, based on the capacity
reduction required or provided credit for in the water-efficient home(s) under the PCM.

• Step 2: Similar to Step 3 of Option 1, subtract water savings for the technologies
and practices listed in Sections 4.4.2.1.2 and 4.4.2.1.3 from the baseline TIR to
determine the final use for the water-efficient landscape.

EPA is not including savings from irrigation technologies that impact irrigation system flow rate,
such as microirrigation, WaterSense labeled spray sprinkler bodies, or pressure regulation at
the valve. These savings are already accounted for in the capacity reduction captured by
reduction in RICI, since RICI is a ratio that includes the total flow rate of the system.

4.5 Other Water Uses

While EPA's technical evaluation is meant to assess all quantifiable water uses (and respective
savings) expected for a home, it is possible that there are other potential water uses and/or
savings for which EPA has not accounted. If an HCO believes that water use or savings from a
requirement or feature of its PCM is not adequately accounted for, the HCO can submit
technical justification to EPA for consideration. Technical justification shall include, but is not
limited to:

•	The expected impact on water use per household per day or per occupant per day for
standard models or standard design.

•	The expected water savings per household per day or per occupant per day from
incorporation of more efficient product models or system design.

•	Studies, data, and other supporting materials on the use of the specific design or
technology in the field that supports the HCO's claims.

•	For systems that supply alternative water sources (such as rainwater or greywater
systems), the temporal resolution with which water collection and use is calculated.

•	For systems that supply alternative water sources (such as rainwater or greywater
systems), the percentage of useful water that the system is anticipated to yield after
treatment.

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EPA will review the technical merits of an HCO's request on a case-by-case basis. If sufficient
technical justification is provided and approved, EPA will incorporate anticipated water use
and/or savings for the baseline and water-efficient configuration for each reference home in the
technical evaluation, as applicable.

4.6 Generating Total Water Efficiency Percent Savings

As the last step of the technical evaluation, EPA combines the indoor and outdoor water use
generated for the respective baseline and water-efficient configuration for each reference home
to establish a total water use. Total water use for each water-efficient reference home
configuration, representing the least efficient home design(s) for the PCM, is compared to its
respective baseline reference home configuration to establish a percent savings. If the water
efficiency requirement from the WaterSense Specification for Homes is achieved across each
reference home scenario, EPA will approve the PCM, as discussed in Section 5.0.

5.0 EPA Response to HCOs

Upon technical evaluation, EPA shall issue an evaluation report to the HCO to indicate whether
its PCM demonstrated the ability to consistently differentiate homes that meet the water
efficiency requirements compared to a home with characteristics typical of new construction (as
required in the WaterSense Specification for Homes).

As part of the evaluation process, EPA may submit comments or recommendations to the HCO
for consideration during future revisions to the certification method to further enhance the water
efficiency and/or performance requirements. Upon request from the HCO, EPA may also
provide recommendations for PCMs that do not consistently differentiate homes that meet
EPA's water efficiency requirements. Following revision to its certification method, an HCO can
resubmit a PCM for technical evaluation.

EPA will license HCOs whose PCMs are capable of consistently achieving WaterSense's
efficiency requirements for homes in accordance with the WaterSense Home Certification
System. The PCM will subsequently be designated as a WACM.

As discussed in the WaterSense Homes Certification System, EPA's intent is to recognize a
WACM for a period of five (5) years, as long as it is not revised by the HCO such that the
revisions could impact its ability to differentiate homes that meet EPA's water efficiency
requirement.

6.0 Amendments, Modifications and Revisions

As required under the WaterSense Home Certification System, an HCO shall notify EPA in
writing of any changes to its WACM that could materially affect its performance under EPA's
technical evaluation. Notification shall be made at least 60 days prior to the implementation of
such changes and with sufficient time to allow for EPA to evaluate the changes and determine if
the WACM will continue to meet the efficiency requirements of the WaterSense Specification for
Homes. EPA shall evaluate revisions to the HCO's WACM using the latest version of the
WaterSense Technical Evaluation Process for Approving Home Certification Methods.

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EPA

WaterSense* Technical Evaluation Process for
Approving Home Certification Methods

WaterSense

EPA also reserves the right to revise the technical evaluation process, as described in the
WaterSense Home Certification System. EPA will consider revisions should: 1) national product
and appliance efficiency standards or typical construction characteristics change in the future
such that it affects baseline water use estimates; 2) better data on water use by products,
appliances, systems, and/or the whole household become available; and/or 3) technological
and/or market changes affect its usefulness to consumers, industry, or the environment.

As described in the WaterSense Home Certification System, EPA will only make major revisions
to the technical evaluation process following an open public process, including discussion with
builders, HCOs, verifiers, and other interested stakeholders. Major revisions will typically require
re-approval of existing WACMs to the new technical evaluation or the WaterSense Home
Certification System. Minor revisions or technical clarifications will generally be editorial in
nature and serve to clarify vague or unclear requirements and will not require reapproval.

7.0 More Information

For inquiries or other questions related to this technical evaluation process document, the
WaterSense Specification for Homes, or the WaterSense Labeled Homes Program, please
contact the WaterSense Helpline at (866) WTRSENS (987-7367) or watersense@epa.gov.

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