WaterSense
WaterSense Draft Specification for Showerheads
Supporting Statement
WaterSense® Draft Specification for Showerheads
Supporting Statement
I. Introduction
Showering is one of the leading uses of water inside the home, representing approximately 17
percent of annual residential indoor water use in the United States. This translates into more
than 1.2 trillion gallons of water consumed each year.1,2 WaterSense is releasing for public
comment a draft specification for showerheads to capitalize on this opportunity to raise
consumer awareness, further improve water and energy efficiency, and promote the use of
more efficient showerheads. The intent of this specification is to help consumers identify and
differentiate those products that have met EPA's criteria for water efficiency and performance.
WaterSense collaborated with the American Society of Mechanical Engineers
(ASME)/Canadian Standards Association (CSA) Joint Harmonization Task Force to develop the
draft specification criteria for high-efficiency showerheads. This task force is open to the public
and comprises a wide variety of stakeholders including showerhead manufacturers, water and
energy utilities, testing laboratories, consultants, and other water-efficiency and conservation
specialists. Their participation, resources, and expertise enabled WaterSense to evaluate
showerhead efficiency and performance and develop meaningful testing protocols that can
effectively differentiate showerhead performance.
This is important because prior to the task force's work there were no universally accepted
criteria for measuring showerhead performance. Federal water-efficiency legislation and
national performance standards only establish product flow rates that dictate water
consumption—they do not address what makes a satisfactory, or unsatisfactory, shower. Now,
with this draft specification, WaterSense and the task force have bridged this consumer
information gap by incorporating performance requirements for products that can earn the
WaterSense label. The proposed requirements address flow rate across a range of pressure,
spray force, and spray coverage, three key attributes of showerhead performance, according to
consumer testing. These new requirements are designed to ensure a high level of performance
and user satisfaction with high-efficiency showerheads.
II. Current Status of Showerheads
Wth nearly 110 million occupied housing units in the United States3 and an average of two
showerheads per household4, WaterSense estimates that there are 220 million showerheads
currently installed in homes across the United States. WaterSense also estimates that
1 Assumes a per capita shower use of 11.6 gallons. See Mayer, Peter W. and William B. DeOreo.
Residential End Uses of Water. Aquacraft, Inc. Water Engineering and Management. American Water
Works Association. 1998. Page 102.
2 According to the U.S. Census Bureau, there are 300 million persons in the United States.
3 See U.S. Census Bureau and the U.S. Department of Housing and Urban Development's American
Housing Survey for the United States. 2007.
4 Mayer and DeOreo, op. cit., 99.
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WaterSense Draft Specification for Showerheads
Supporting Statement
approximately 10 percent of the existing 220 million showerheads are replaced each year due to
wear, remodeling, or other reasons. This means that the vast majority of these existing
showerheads have flow rates equal to or less than the federal standard of 2.5 gallons per
minute (gpm), which was mandated by the Energy Policy Act (EPAct) of 1992. With normal
replacements and units sold for new construction, WaterSense estimates that approximately
23.8 million5 new showerheads are sold each year. Since Congress enacted the federal
requirements in the early 1990s, manufacturers have gone on to develop showerheads that use
significantly less water than the flow rates set in EPAct 1992. These high-efficiency
showerheads can save at least 20 percent compared to standard fixtures, resulting in a potential
savings of more than 1,200 gallons per showerhead per year.
III. WaterSense Specification for Showerheads
Scope
This draft specification applies to showerheads and hand-held showers. Showerheads are fixed
devices for directing water onto a user for bathing purposes. Hand-held showers, a subset of
showerheads, are moveable devices for directing water onto a user. Hand-held showers can be
installed on a support to function as a showerhead.
Multiple showerheads are eligible to receive the WaterSense label provided the showerheads
are sold in combination in a single device intended to be connected to a single shower outlet.
Further, each showerhead must meet all of the requirements of the specification and the entire
multiple-head system must meet the maximum flow rate requirement of the specification in all
possible operating modes.
Body sprays are excluded from this specification because their function and design are wholly
different than that of a showerhead or hand-held shower. Retrofit devices, including aftermarket
flow control devices, are also excluded because the intent of the specification is to recognize
and label complete, fully functioning fixtures or fittings, and not individual components.
General Criteria
Many showerheads are sold with multiple modes to provide the user with options for different
spray types (e.g., misting, massaging, or pause). WaterSense wants to maintain manufacturing
flexibility and consumer choice for multiple mode showerheads, thus the draft specification
addresses these types of showerheads by requiring all modes to meet the maximum flow rate
requirement (i.e., no mode can exceed 2.0 gpm) and at least one of the modes, as specified by
the manufacturer, must meet all of the requirements contained in the specification, including the
maximum and minimum flow rates, spray force, and spray coverage requirements.
5
Units sold for replacement is based upon a 10 percent natural replacement rate. Units sold for new
construction is based on 906,000 housing starts in 2008 as reported in the U.S. Census Bureau, Housing
Starts, Construction Reports, Series C-20.
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Water-Efficiency Criteria
The water-efficiency component of this draft specification establishes a maximum flow rate of
2.0 gpm (7.6 liter per minute [Lpm]). WaterSense settled on this flow rate after examining the
range of products currently available on the market. This maximum flow rate represents a 20
percent reduction from the current federally allowable maximum flow rate of 2.5 gpm
established by EPAct 1992, which is consistent with WaterSense's stated water-efficiency goal.
The draft specification also includes minimum flow rate requirements at 80, 45, and 20 pounds
per square inch (psi) of pressure (the upper, mid, and lower range of potential household
pressures) to ensure performance and user satisfaction under a variety of household conditions.
Specifically, at 45 and 80 psi the tested flow rate cannot be less than 75 percent of the
showerhead's maximum "rated"6 flow rate value. This minimum requirement is specified at both
45 and 80 psi because some showerheads that are designed to provide pressure compensation
will actually produce maximum flow at 45 psi. Likewise, at 20 psi the tested flow rate cannot be
less than 60 percent of the showerhead's maximum rated flow rate value. Table 1 below
provides some examples of the allowable minimum flow rates for showerheads with various
rated flow rates. Defining minimum flow rate requirements in this manner ensures that the
showerhead is designed to provide consistent flow across a range of pressures.
Tab
e 1. Example Minimum Flow Rates
Showerhead
Minimum Allowable Flow Rate
Rated Flow Rate
80 psi
45 psi
20 psi
2.0 gpm
1.5 gpm
1.5 gpm
1.2 gpm
1.75 gpm
1.3 gpm
1.3 gpm
1.1 gpm
1.5 gpm
1.1 gpm
1.1 gpm
0.9 gpm
1.0 gpm
0.8 gpm
0.8 gpm
0.6 gpm
WaterSense is requiring both the maximum and minimum flow rates of the showerhead to meet
the testing and verification protocols for sampling outlined in the Code of Federal Regulations
(see 10 CFR 430 Subpart F, Appendix B, Steps 6[b] and 6[a], respectively). The U.S.
Department of Energy currently uses the sampling plan outlined in the CFR for assessing
compliance of showerhead flow rates with EPAct 1992 requirements, and thus referencing it in
this specification provides specific and familiar guidance to third-party certifying bodies for
determining whether a showerhead meets the flow rate requirements established by
WaterSense.
Performance Criteria
Establishing performance-based criteria for WaterSense labeled showerheads is critical to
ensuring user satisfaction and maintaining the integrity of the WaterSense label. Prior to this
draft specification, however, there were no universally agreed-upon testing protocols for
showerhead performance or measures that adequately defined user satisfaction. WaterSense
worked with the task force to determine, through its expertise and supported by consumer
testing, the key performance attributes of showerheads. To measure those attributes in a
6 The "rated" flow rate is the showerhead's maximum flow rate, as specified by the manufacturer, verified
through testing, and in compliance with this specification.
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laboratory setting, the task force undertook an intensive effort to develop test protocols. The
spray force and spray coverage requirements contained in the draft specification are a result of
these efforts. Both test protocols subsequently underwent several iterations of round robin
testing in various laboratories by multiple manufacturers and independent third-party certifiers in
order to ensure that the procedures are repeatable and the results reproducible. Laboratory test
data were then compared back to the consumer test data for a variety of showerheads to
determine the specific performance levels that are included in the draft specification. These
performance levels define the boundaries for user satisfaction for both spray force and spray
coverage.
The spray force component of the specification requires a showerhead's spray force to be at
least 2.0 ounces (0.56 newtons [N]) at an inlet pressure of 20 psi when the water is flowing. The
testing procedure, described in Appendix A of the specification, is a pass/fail test that assesses
the relative force of the shower spray through the use of a force balance fixture. The force
balance fixture is equipped with a force target on one side that receives the shower spray and
counterbalancing weights on the other side, set to the specified force (i.e., 2.0 ounces). As the
shower spray hits the force target, the force balance fixture measures the rotation angle of the
balance at the pivot point of the two sides (the spray and counterbalancing weights). If the
shower spray force is greater than the specified minimum, it will overcome, or move, the
counterbalancing weights to or beyond the point of balance, achieved when the rotation angle is
equal to or greater than 0.0 degrees. Under this scenario the showerhead would pass the force
requirements. If the showerhead's force is less than the specified minimum, it will not overcome
the counterbalancing weights and the angle of balance will not rotate past 0.0 degrees. Under
this scenario, the showerhead would fail the force requirements. The specific target force
proposed in the draft specification represents the lower bounds of user satisfaction based on
results from consumer tests using a variety of showerheads.
The spray coverage component of the specification, as described in Appendix B of the
specification, requires the use of an annular ring gauge consisting of a series of 10 concentric
rings, starting with a 2-inch diameter center ring and each successive ring increasing in
diameter by 2 inches. The showerhead is positioned and turned on directly above the surface of
the annular ring gauge. The relative amount of water captured in each set of concentric rings
provides a representation of the distribution of the spray pattern and can be used to evaluate
the showerhead's spray coverage. Simultaneous to the development of the test apparatus,
WaterSense gathered consumer test data to determine user preferences with regard to spray
coverage. Data showed general dissatisfaction with showerheads that spray with a hollow spot
in the center or that have too much water flowing in the center to form a very narrow beam.
Thus the criteria contained in the draft specification were crafted to capture and disqualify
showerheads with these types of coverage characteristics. Specifically, to meet the spray
coverage requirement, the total volume of water collected in the two center rings (out to 4
inches) cannot exceed 75 percent of the total collected water volume (i.e., the showerhead
cannot deliver all its water through a narrow beam in the center). In addition, the total combined
volume of water collected in the three center rings (out to 6 inches) must be at least 25 percent
of the total collected water volume (i.e., the showerhead cannot have a hollow spot in the
center).
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WaterSense Draft Specification for Showerheads
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Product Marking
With this specification, WaterSense has adopted a new approach to product and package flow
rate marking. The requirements are designed to clarify and clearly indicate which maximum flow
rate value the manufacturer is to use. At the outset of certification, the manufacturer specifies a
maximum flow rate value ("rated" flow rate), not to exceed 2.0 gpm, which is subsequently
verified through testing. WaterSense requires the manufacturer to mark the product and product
packaging with this rated flow rate value, so that the information provided to the consumer is
both informative and accurate.
In addition to marking the product and packaging with the maximum rated flow rate, the product
packaging (but not the product itself) must also be marked with the showerhead's minimum flow
rate at 45 psi. As with the maximum flow rate value, this minimum flow rate is specified by the
manufacturer at the outset of certification and is subsequently verified through testing. The
purpose of this marking requirement is to assist installers in properly matching showerheads
and automatic-compensating mixing valves for installation in order to provide protection against
thermal shock and scalding events (see Section V below for more information). This additional
marking requirement can be found in the Appendix C: Informative Annex for WaterSense
Labeling of the draft specification. It is separated from the marking requirements in the body of
the specification because it is not required by existing standards or federal regulations and it is a
requirement unique to products with packaging that will bear the WaterSense label.
Potential Water and Energy Savings
Note: Refer to Appendix A for the assumptions and calculations used to derive these estimates.
Showerheads with a flow rate of 2.0 gpm or less have the potential to save significant amounts
of water both individually and at the national level. Replacing standard showerheads with
WaterSense labeled showerheads could save more than 1,200 gallons per showerhead or
2,300 gallons of water per household per year. Nationwide, if all 220 million showerheads were
replaced with WaterSense labeled models, more than 260 billion gallons of water could be
saved each year.
Based upon the amount of water saved, the average household could save 300 kilowatt hours
(kWh) of electricity or 1,500 cubic feet of natural gas that would otherwise be required to heat
the water. National energy savings could exceed 14 billion kWh of electricity and 94 million
cubic feet (Mcf) of natural gas each year.
Cost-Effectiveness
Note: Refer to Appendix A for the assumptions and calculations used to derive these estimates.
The average homeowner retrofitting his or her showerheads with WaterSense labeled
showerheads will realize an accompanying $14 savings on water and wastewater costs
annually due to lower water consumption. Factoring in the accompanying energy savings, the
average household with electric water heating may save an additional $33, for a combined
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Supporting Statement
annual savings of $47. The average household with natural gas water heating may save an
additional $18 for a combined annual savings of $32.
If the average showerhead costs $30 retail, the average payback period for the replacement of
two standard showerheads per household with WaterSense labeled models would be
approximately 15 months for those with electric water heating and about two years for those
heating with natural gas.
IV. Certification and Labeling
WaterSense has established an independent third-party product certification process, described
on the WaterSense Web site at www.epa.gov/watersense/specs/certification.htm. Under this
process, products are certified to conform to applicable WaterSense specifications by
accredited third-party licensed certifying bodies. Manufacturers are then authorized to use the
WaterSense label in conjunction with certified products.
V. Other Issues
Detailed Drawings for the Force Balance Test Apparatus
As the specification indicates, the spray force performance requirement is measured via a force
balance test apparatus. This force balance test apparatus was developed by the task force
specifically for the purpose of determining a showerhead's compliance with the specification's
force requirements; therefore it is not a readily available or mass-produced piece of testing
equipment. In addition, the test apparatus needs to be manufactured with very specific
tolerances to ensure the results are repeatable and reproducible in any laboratory setting.
WaterSense has made available the specification drawings to facilitate the construction of this
test equipment. Detailed drawings for the force balance test apparatus are available on the
WaterSense Web site at www.epa.gov/watersense/pp/showerheads.htm.
Health and Safety
In developing this draft specification, WaterSense and the task force considered potential
negative impacts of reducing the flow rate on consumer satisfaction, including potential health
and safety issues once these products are installed in the plumbing system. Of particular
concern is the potential for increasing the risk of thermal shock or scalding as shower flow rates
are reduced. Thermal shock or scalding can be caused when a hot- or cold-water-using device
is activated while the shower is running. Water is diverted away from the shower, causing a
pressure drop in either the hot or cold water supply line to the shower. As a consequence, the
balance of hot and cold water is shifted either to a hotter or colder temperature mix. This sudden
change in temperature can either cause a user to abruptly move away from the shower stream,
potentially resulting in an injury or fall, or if the temperature increase is severe enough, scalding
can occur.
To mitigate the risks of temperature-related shower injuries, most U.S. plumbing codes require
showers to be outfitted with individual automatic-compensating mixing valves that comply with
either the American Society of Sanitary Engineers (ASSE) 1016 or ASME A112.18.1/CSA
B125.1 standards. An automatic-compensating mixing valve is a device that is installed as part
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of the shower's flow control that helps to regulate water temperature, it is not part of the
showerhead itself. The valve works either through balancing the incoming hot and cold water
pressures or through controlling the mixed outlet temperature with a thermostatic element that
can maintain water temperature to within +/- 3.6°F.
Despite advances in plumbing codes and mixing valve technology, thermal shock and scalding
risks are still present under two scenarios. First, automatic-compensating mixing valves are
currently only required to be tested and certified at a flow rate of 2.5 gpm at 45 psi. When these
devices are outfitted in conjunction with a showerhead that has a lower flow rate, there may not
be adequate assurance that the valve is sensitive enough to provide the required protection.
This is potentially true for all showerheads, as standard showerheads are currently tested and
certified at a flow rate of 2.5 gpm at 80 psi. Second, not all homes are equipped with an
automatic-compensating mixing valve. The risks are of particular concern for showerhead
retrofits in homes built prior to 1987.
As a part of the development of the criteria for showerheads, WaterSense and the task force
evaluated the link between flow rate and temperature deviations associated with pressure and
temperature changes. The task force gathered and presented data to compare the temperature
profiles that result from a drop in hot and cold water pressure for both standard and high-
efficiency showerheads under the two risk scenarios: 1) installation with various types of
automatic-compensating mixing valves (thermostatic, pressure balancing, or combination)
designed for a flow rate of 2.5 gpm at 45 psi and 2) installation without the protection of an
automatic-compensating mixing valve. The data showed that the risks are present for
showerheads of all flow rates, but that more efficient showerheads are more sensitive to sudden
changes in water pressure. As a consequence, temperature change in water exiting the shower
may be amplified when the pressure within the cold water or hot water supply plumbing changes
suddenly.
Ultimately, WaterSense and the task force came to the conclusion that the thermal shock and
scalding risks cannot be fully addressed through the specification for showerheads. First, there
is a clear disconnect between the showerhead and automatic-compensating mixing valve
compatibility, as the products are tested at different pressures (80 psi and 45 psi, respectively)
and currently automatic-compensating mixing valves are only tested at a flow rate of 2.5 gpm.
Second, the potential temperature of the hot water is controlled by the design of the hot water
heater and delivery system, that can discharge water well in excess of the code required 140°F
due to "layering" and the location of the thermostat at a point that is not necessarily the location
of the hottest water. Because of the interrelated nature of these three components in the
plumbing system, the control of the risks cannot solely rest on the design of the showerhead. In
fact, the showerhead itself has very little, if any, control over the outlet water temperature.
What WaterSense can do and has done to address this issue in the draft specification is to
require the manufacturers to mark the product packaging with the minimum flow rate at 45 psi
as determined by testing at that pressure. This is a vital step toward providing the information
necessary to "match" the showerhead with a compatible automatic-compensating mixing valve
that is rated to provide protection at the same flow rate and tested pressure. WaterSense also
will continue to work with ASSE and ASME to revise the existing standards for mixing valves.
This work will ensure that mixing valves are compatible with high-efficiency showerheads so
that when used in combination, they provide the necessary protection against thermal shock
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and scalding. In addition, WaterSense is preparing materials to help educate its partners and
consumers regarding the issue and associated risks so that consumers can continue to make
informed purchasing decisions.
VI. Request for Comments and Data
At this time WaterSense is interested in receiving comments on any and all aspects of the
proposed draft specification. Comments should be submitted to WaterSense in writing at
watersense-products@erq.com.
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Appendix A: Calculations and Key Assumptions
Potential Water Savings Calculations
Assumptions:
• Average actual flow rate for an existing showerhead is 2.22 gpm7 (the average flow rate
is less than the standard rated flow rate of 2.5 gpm most likely because the products are
rated at 80 psi, but installed in homes with less pressure)
• Average shower duration is 8.2 minutes8
• The average person takes 0.67 showers per day9
• A WaterSense labeled showerhead reduces the flow rate by 20 percent
Equation 1. Annual Water Savings From Replacing a 2.5 gpm Rated Showerhead
((2.22 gpm - (2.22 x (1-0.2))) x 8.2 minutes/shower x 0.67 showers/person/day x 2.6
people/household x 365 days/year) = 2,300 gal/household/year
(2,300 gal/household/year / 2 showerheads/household) = 1,200 gal/showerhead/year
Equation 2. Annual National Water Savings From Replacing 2.5 gpm Showerheads
(1,200 gal/showerhead/year x 220 million showerheads) = 260 billion gal/year
Unit Abbreviations:
gal = gallon
gpm = gallons per minute
psi = pressure per square inch
Potential Energy Savings Calculations
Assumptions:
• Approximately 73 percent of showerhead water used in a household is hot water10
• 42,239,000 (approximately 40 percent) of occupied residences in the United States heat
their water using electricity11
• 60,998,000 (approximately 56 percent) of occupied residences in the United States heat
their water using natural gas11,12
• Water heating consumes 0.18 kWh of electricity per gallon of water heated assuming:
o Specific heat of water =1.0 Btu/lb x0 F
o 1 gallon of water = 8.34 lbs
7 Mayer and DeOreo, Op. cit., 102.
8 Calculated based upon an assumed 17.2 gallons per shower and 11.6 gallons per day for showering.
(Ibid.).
Calculated based upon an assumed 17.2 gallons per shower and 11.6 gallons per day for showering.
(Ibid.)
0 DeOreo, William B., and Peter W. Mayer. The End Uses of Hot Water in Single Family Homes From
Flow Trace Analysis. 2000. Aquacraft, Inc.
11 U.S. Department of Housing and Urban Development and U.S. Census Bureau. American Housing
Survey for the United States: 2007. 2008. Table 1A-5, page 7..
12 Ibid.
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o 1 kWh = 3,412 Btus
o Incoming water temperature is raised from 55° F to 120° F (A 650 F)
o Water heating process is 90 percent efficient for electric hot water heaters
• Water heating consumes 0.88 Mcf of natural gas per 1,000 gallons of water heated
assuming:
o Specific heat of water =1.0 Btu/lb x0 F
o 1 gallon of water = 8.34 lbs
o 1 Therm = 99,976 Btus
o Incoming water temperature is raised from 55° F to 120° F (A 650 F)
o Water heating process is 60 percent efficient for natural gas hot water heaters
Electricity
Equation 3. KWh Required to Raise 1 gallon of Water 65° F
[(1 gal x 1.0 Btu/lbs x 0 F) (1kWh/3,412 Btus) I (1 gal/8.34 lbs) x 65° F] I 0.90 = 0.18 kWh/gal
Equation 4. Electricity Saving per Household
(2,300 gal/year x 0.73) x (180 kWh of electricity/1,000 gal) = 300 kWh of electricity per year
Equation 5. National Electricity Savings Potential
(260 billion gal x 0.73 x 0.40) x (180 kWh of electricity/1,000 gal) = 14 billion kWh of electricity
nationwide
Natural Gas
Equation 6. Therms Required to Raise 1 gallon of Water 65° F
[(1 gal x 1.0 Btu/lbs x 0 F) (1 Therm/99,976 Btus) I (1 gal/8.34 lbs) x 65° F] I 0.60 = 0.009
Therms/gal
Equation 1. Converting Therms to Mcf
0.009 Therms/gal x 1,000 gal x 1 Mcf/10.307 Therms = 0.88 Mcf/kgal
Equation 8. Natural Gas Savings per Household
(2,300 gal/year x 0.73) x (0.88 Mcf of natural gas/1,000 gal) = 1.5 Mcf (1,500 cubic feet) of
natural gas per year
Equation 9. National Natural Gas Savings Potential
(260 billion gal x 0.73 x 0.56) x (0.88 Mcf of natural gas/1,000 gal) = 94 Mcf of natural gas
nationwide
Unit Abbreviations:
Bcf = billion cubic feet
Btu = British thermal unit
F = Fahrenheit
kgal = kilogallons
kWh = kilowatt hour
lbs = pounds
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Mcf = thousand cubic feet
Cost-Effectiveness Calculations
Assumptions:
• Price of electricity is $0.11/kWh13
• Price of natural gas is $11,88/Mcf14
Equation 10. Annual Water and Wastewater Cost Savings
2,300 gallons/year x $6.0615/1,000 gallons = $14
Equation 11. Average Payback Period (Electric Water Heating)
($30/showerhead x 2 showerheads/household) / $47 saved per year =1.3 years (-15 months)
Equation 12. Average Payback Period (Natural Gas Water Heating)
($30/showerhead x 2 showerheads/household) / $32 saved per year =1.9 years
13 U.S. Department of Energy, www.eia.doe.gov/cneaf/electricitv/epm/table5 3.html.
14 U.S. Department of Energy, www.eia.doe.gov/steo.
15 Raftelis Financial Consulting. Water and Wastewater Rate Survey. American Waterworks Association.
2006.
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