WaterSense5M Tank-Type High-Efficiency Toilet Specification
       WaterSense® Tank-Type High-Efficiency Toilet Specification
I.      Introduction

The WaterSense Program released its performance specification for tank-type high-efficiency
toilets (HETs) (Specification) on January 24, 2007, to promote and enhance the market for
water-efficient toilets. The goal of this Specification is to differentiate products in the
marketplace that meet this Specification's criteria for efficiency and performance and help
consumers identify these water-efficient products.

This Specification addresses toilets typically found in homes, and in light commercial settings,
such  as hotels and restaurants. It does not address valve-type commercial toilets typically found
in public restrooms (e.g., airports, theaters, arenas, schools) or composting toilets, both of which
have different designs,  patterns of use, and performance requirements.

II.     Current Status of Toilets

WaterSense estimates  there are currently 222 million residential toilets in the United States.
This estimate is based on an assumed one-to-one ratio of toilets to bathrooms.1 In addition to
the existing stock, approximately 10 million new toilets are sold each year for installation in new
homes or replacement of aging fixtures in existing homes.2 Residential toilets account for
approximately 30 percent of indoor residential water use in the United States—equivalent to
more than 2.1 trillion gallons of water consumed  each year.3

The Energy Policy Act of 1992 established the maximum flush volume for all gravity tank-type,
flushometer tank, and electromechanical hydraulic toilets at 1.6 gallons per flush (gpf). These
requirements are codified in the Code of Federal Regulations at 10 CFR Part 430 (specifically
§430.32(q) Water Closets). Federal regulations also require that all toilets sold in the United
States be tested and certified in accordance with the test requirements specified in American
Society of Mechanical Engineers (ASME) A112.19.2-Vitreous China Plumbing Fixtures and
Hydraulic Requirements for Water Closets and Urinals. All dual-flush toilets sold in the United
States also must comply with ASME A112.19.14-Six-Liter Water Closets Equipped with a Dual
Flushing Device.

In addition, there are several voluntary, non-certification toilet testing programs. These tests are
frequently required by water utilities for toilets to  qualify for rebates under local water
conservation  toilet replacement programs. Two of the most popular and widely used voluntary
testing programs in North America are the Maximum Performance (MaP) Testing of Popular
Toilet Models and the Los Angeles Department of Water and Power Requirements for Ultra-
Low-Flush-Toilets, Supplementary Purchase Specification to ASME A112.19.2 (LADWP SPS).
1 U.S. Census Bureau, American Housing Surveys for the United States, 1970-2003.
2 Plumbing Fixtures market Overview: Water Savings Potential for Residential and Commercial Toilet and
Urinals. D&R International. September 30, 2005
3 Mayer, Peter W. and William B. DeOreo. Residential End Uses of Water. Aquacraft, Inc. Water
Engineering and Management. American Water Works Association. 1998.
                                                                            February 9, 2007

                                     WaterSense5M Tank-Type High-Efficiency Toilet Specification
MaP is entirely performance based, testing a toilet's maximum ability to remove waste starting
with a  50 gram soybean paste sample and increasing at 50 gram intervals. A minimum passing
score is 250 grams. The LADWP SPS requires the use of durable, chemical-resistant flush
valve seals, and restricts maximum flush volumes under maximum trim adjustment and
pressure conditions.

One problem with the number of different voluntary toilet testing programs in existence was the
lack of uniformity or consistent requirements. Manufacturers found it difficult and costly to
develop products that met the requirements of multiple  testing programs, and water authorities
were unsatisfied with the limited availability of qualified  products. Consumers found the
patchwork of toilet specifications, requirements, and "approved toilet lists" confusing at best. To
remedy this situation, in 2004, members of the plumbing industry and water utilities combined
the MaP Testing and LADWP SPS standards to create  the Uniform North American
Requirements (UNAR)  for Toilet Fixtures: Guidelines and Specifications.  UNAR is a voluntary
system for qualifying toilet fixtures that achieve sustainable water savings and ensure a high
level of customer satisfaction with flushing performance.

In developing this Specification, WaterSense adopted the framework of the UNAR standard
while making several significant changes to the water-efficiency and performance criteria.
WaterSense estimates that there are currently 68 toilet  models on the market that meet the
requirements of this specification and would be qualified to apply for and  use the WaterSense

III.    WaterSense Tank-Type High-Efficiency Toilet Specification

The WaterSense Program developed this Specification to address criteria for improvement and
recognition of water-efficient and high-performance tank-type toilets. These toilets are
commonly found in residential and light  commercial settings and include the standard gravity
type found in most homes, pressure assisted, and electrohydraulic assisted toilets. The majority
of these fixtures are single flush toilets,  toilets with one  constant flush volume, though an
increasing number of dual flush models  are coming to market. Dual flush toilets have two flush
volumes—a full flush for solids and a reduced flush for  liquids only. WaterSense initially focused
on residential toilets because they are the largest water consuming fixture in homes.

Commercial valve-type (a.k.a., flushometer valve) toilets were excluded from this specification
because of their differing design, patterns of use, and performance expectations. Commercial
valve-type toilets are tankless, relying on water pressure controlled by flushing valves to remove
waste  rather than gravity. Because of the fundamental difference in design, a different set of
technical requirements is needed. Commercial valve-type toilets also have a different pattern of
use than residential or light commercial  tank-type toilets and will likely require different
performance specifications. For example, the test media needing to be cleared by a commercial
valve-type toilet may need to include a paper toilet seat cover and potentially more paper. If
WaterSense decides to address this type of toilet, it will do so under a separate specification  at
a later time.

Water Efficiency Criteria
                                                                            February 9, 2007

                                     WaterSense5M Tank-Type High-Efficiency Toilet Specification
The water-efficiency component of the Specification establishes a maximum effective flush
volume of 1.28 gpf for all HETs. This value represents a 20 percent reduction from the current
1.6 gpf standard and is consistent with WaterSense's stated goal of increasing product
efficiency by at least 20 percent. Under this Specification, there are two ways by which an MET
can meet the effective flush volume criteria:

       Single flush toilet must use 1.28 gpf or less; or
       Dual flush toilets must have a full flush no more than 1.6 gpf and a reduced flush no
       more than 1.1 gpf. Field studies indicate that in actual use such toilets will flush 1.28 gpf
       or less, on average.

Performance Criteria
In light of the history of poor performance and user dissatisfaction with several  of the early 1.6
gpf ultra-low flush (ULF) toilets in the early 1990's, WaterSense wanted to ensure that
WaterSense labeled HETs consistently perform at a high level and meet or exceed user
expectations. The Flush Performance Criteria (Section 4.0) of the Specification ensures this
level of performance and is based on the UNAR standard, with  two key differences.  First, the
WaterSense specification increased the mass of the soy bean paste test media from 250 grams
to 350 grams. WaterSense decided to  make the Specification more rigorous in order to
establish a higher level of performance for HETs and ensure  customer satisfaction with these

Second, WaterSense also decided to switch from cased media, as used in UNAR, to an
uncased media.  Several manufacturers reported variability in test results when using cased
media and expressed concern  over the sample  reliability. In addition, the primary justification for
using cased media—reusability to save time and reduce costs—while important requirements in
a research and development mode when many  repeated tests are performed, were not as
critical in regards to this HET specification, as a maximum of only five tests are required. The
uncased media provides a more realistic sample and has a more established testing track
record. For these reasons, WaterSense adopted the use of uncased media.

Potential Water Savings
The 222 million residential toilets in use today are a mix of the current standard 1.6 gpf fixtures
and older, pre-1992 models. Water consumption in these older  models range from 3.5 gpf to
more than 5.0 gpf, depending on age and model. Table 1 provides a breakdown of the mix of
the existing toilet stock.

To estimate the potential water savings impact of HETs, WaterSense assumed that the average
person flushes 5.1 times per day at home.4 Wth an estimated population of 296  million people
in the United States and 222 million residential toilets in use,  this equates to 6.8
flushes/toilet/day (see Calculation 1). Assuming that 10 percent of the existing 222 million toilets
in the United States could reasonably be expected to be replaced with WaterSense labeled
HETs, the total daily savings potential is approximately 246 million gallons per day (see Table 1
and Calculation 2). This equates to more than 89.7 billion gallons  each year (see Calculation 3).
4 Peter W. Mayer and William B, DeOreo. Residential End Uses of Water. Aquacraft, Inc. Water
Engineering and Management. American Water Works Association. 1998. p. 94.
                                                                            February 9, 2007

                                      WaterSense5M Tank-Type High-Efficiency Toilet Specification
                       Calculation 1.Average Daily Flushes per Toilet

(5.1 flushes/person/day)(2.96 x 108 people) / (2.22 x 108 toilets) = 6.8 flushes/toilet/day

Table 1. Number of Toilets by Flush Volume and Potential Savings5
# of toilets (millions)
# of toilets replaced given
10% replacement of
existing fixtures (millions)
Savings per flush by
switching to 1.28 MET
                              Calculation 2. Total Daily Savings
                   (If 10% of all existing toilets replaced with 1.28 gpf MET)

     5.0 gpf: (6.7 x 106 toilets) (3.72 gpf) (6.8 flushes/toilet/day) =     169,483,200 gallons/day

     3.5 gpf: (3.3 x 106 toilets) (2.22 gpf) (6.8 flushes/toilet/day) =     49,816,800 gallons/day

     1.6 gpf: (12.2 x 106 toilets) (0.32 gpf) (6.8 flushes/toilet/day) =    26,547,200 gallons/day

     Total Daily Savings                                           245,847,200 gallons/day

                            Calculation 3. Total Annual Savings

     (245,847,200 gallons/day) (365 days/year) =   89,734,228,000 gallons/year
                                                  89.7 billion gallons/year
 Plumbing Fixtures market Overview: Water Savings Potential for Residential and Commercial Toilet and
Urinals. D&R International. September 30, 2005
                                                                              February 9, 2007