4

EPA

WaterSense

WaterSense® Draft Specification for Point-of-Use
Reverse Osmosis Systems Supporting Statement

WaterSense® Draft Specification for Point-of-Use Reverse Osmosis

Systems Supporting Statement

I. Introduction

The U.S. Environmental Protection Agency's (EPA's) WaterSense program has developed this
draft specification for point-of-use (POU) reverse osmosis (RO) systems to promote and
enhance the market for water-efficient RO models. The intent of the WaterSense specification is
to help manufacturers produce and sell water-efficient RO systems that meet EPA's criteria for
performance to earn the WaterSense label The WaterSense label, in turn, helps purchasers
more easily identify products that use less water and perform as well as or better than standard
models.

A POU RO system is a water treatment system that is connected to a single fixture (e.g., at the
kitchen sink) and uses the RO process to remove contaminants from the incoming water supply
to that fixture. RO is the process by which pressure forces water through a semi-permeable
membrane, creating a stream of treated water, called "permeate," and a stream of reject water,
called "concentrate" or "brine," consisting of water with more concentrated contaminants that
were unable to pass through the membrane. Figure 1 shows a diagram of a typical point-of-use
RO system that would be installed under a kitchen sink. In most systems, the permeate is sent
to a storage tank, so it can be readily available to users when they dispense water from the tap.
The concentrate is sent to the drain and ultimately becomes wastewater.

Reject
Water to
Drainpipe

Permeate
Pump

Flow

Restrictor

5th Stage

Post Carbon Filter

4th Stage

RO
Membrane

I

Feed Water

Auto Shut
Off Valve

~
H

s.j;

S iis

co

"EJ d)

to £

Storage
Tank

Treated
Water from
RO Faucet

J® 1_

o
cc

I

Figure 1. Diagram of a Typical Point-of-Use RO System

RO systems are effective at reducing common water contaminants of concern such as lead,
copper, chromium, and arsenic. However, these systems also can generate a significant
amount of water waste during operation. A typical POU RO system sends five gallons of water
or more down the drain for every gallon of treated water that it produces.

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Reverse Osmosis Systems Supporting Statement

In recent years, membrane technology has improved, and some POU RO systems have been
designed to operate more efficiently, with some manufacturers advertising systems that send
just one gallon of concentrate down the drain for every one gallon of permeate produced. EPA
is establishing a WaterSense specification to help consumers distinguish RO systems that
operate with greater water efficiency, while still providing the water treatment that consumers
expect.

EPA is aware of concern that the WaterSense label could encourage consumers who would not
otherwise purchase an RO system to buy one, therefore resulting in greater overall water
consumption. In effect, an RO system would be purchased instead of other water treatment
technologies, such as filtration and ultraviolet (UV) treatment, that effectively remove some
contaminants but do not generate any water waste. The intent of this specification is not to
promote RO over other, less water-intensive treatment systems, but rather to help consumers
who already intend to purchase an RO system identify those models that are both water-
efficient and high-performing. EPA does not believe the availability of WaterSense labeled
models will encourage the purchase of RO systems by consumers who would not otherwise
have selected an RO system. This belief is supported by a consumer awareness survey
conducted by EPA in 2022 on WaterSense brand recognition. The survey indicated that
consumers generally become aware of the WaterSense label at the point of purchase or when
doing research before purchase. Once the consumer becomes aware of the meaning, they are
more likely to select a WaterSense labeled model over a standard model.

II. Current Status of POU RO Systems

There is no federal standard that prescribes water efficiency or performance requirements for
RO systems sold in the United States. However, there are a number of applicable industry
standards that specify certification requirements for RO systems. The NSF International
(NSF)/American National Standard Institute (ANSI) 58 Reverse Osmosis Drinking Water
Treatment Systems standard establishes minimum requirements for materials, design and
construction, and performance of POU RO drinking water treatment systems, including
procedures for testing claims of product efficiency and contaminant removal. The two primary
model plumbing codes in the United States (i.e., the International Plumbing Code and the
Uniform Plumbing Code) require POU RO systems to be certified to NSF/ANSI 58.

WaterSense does not have any data on the number of RO systems that are currently in use;
however, WaterSense estimates that approximately one million POU RO systems are sold
annually in the United States. Based on information from industry stakeholders and a review of
products currently available on the market, typical POU RO systems operate at efficiencies
between 10 percent and 20 percent, meaning that they send approximately four to nine gallons
of water down the drain for every gallon of treated water produced.

In 2020, ASSE International (ASSE) released its ASSE 1086 Performance Requirements for
Reverse Osmosis Water Efficiency—Drinking Water standard to establish criteria for
designating water-efficient POU RO systems. ASSE 1086 requires an RO system to achieve a
minimum efficiency of 40 percent, meaning that the system sends 1.5 gallons of water down the
drain or less for every one gallon of treated water produced. However, ASSE 1086 has seen
little uptake in the RO system industry. When conducting product research for this specification,
EPA was only able to identify one system that had been certified to the standard.

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Reverse Osmosis Systems Supporting Statement

While the ASSE 1086 certification has not had a dramatic effect on RO market transformation
towards water-efficient systems, it has created a consensus-based, industry-approved
framework, which EPA intends to build upon—along with NSF/ANSI 58—to encourage the
production and adoption of more efficient RO systems where the installation and use of the
technology is appropriate.

III. WaterSense Specification for Point-of-Use RO Systems
Scope

EPA has developed this specification to address criteria for improving and promoting water-
efficient, high-performing point-of-use RO systems. The scope of this specification is intended to
align with the scope of NSF/ANSI 58 and apply to point-of-use RO systems. However,

NSF/ANSI 58, and by reference NSF/ANSI 330 Glossary of drinking water treatment unit
terminology, do not explicitly define the terms "RO system" or "point-of-use RO systems,"
although they do define other terms that can be used to discern appropriate definitions. ASSE
1086 includes a definition for RO systems, which is also useful for WaterSense's purposes.
Based on a review of NSF/ANSI 58, NSF/ANSI 330, and ASSE 1086, EPA prepared the
following definitions to establish the scope of this specification:

•	RO system: A system that incorporates a water treatment process that removes
undesirable materials from water by using pressure to force the water molecules through
a semipermeable membrane.

•	Point-of-use RO system: A plumbed-in or faucet-mounted RO system used to treat the
drinking and/or cooking water at a single tap or multiple taps, but not used to treat the
majority of water used for washing and flushing or other non-consumption purposes at a
building or facility. Any batch RO system or device not connected to the plumbing
system is considered a point-of-use RO system.

In general, in addition to the RO membrane, all RO systems incorporate filtration stages in their
treatment process, and some will include additional treatment technologies such as UV light.
The additional treatment technologies included in an RO system may therefore fall within the
scope of other NSF/ANSI standards. For example, filters are tested and certified according to
NSF/ANSI 42 Drinking Water Treatment Units—Aesthetic Effects and/or NSF/ANSI 53 Drinking
Water Treatment Units—Health Effects. UV systems are tested and certified according to
NSF/ANSI 55 Ultraviolet Microbiological Water Treatment Systems. Systems containing
multiple, sequential treatment technologies (i.e., treatment trains) fall within the scope of this
specification and will therefore be eligible to earn the WaterSense label. However, while the
WaterSense label is applied to the system as a whole, it is not meant to assess or ensure the
water efficiency and/or performance of the non-RO treatment components. This means that
EPA did not prescribe any water efficiency or performance criteria for non-RO components
within the specification, aside from those included by reference in the NSF/ANSI 58 standard
(see General Requirements). This is based on EPA's understanding that these additional
treatment technologies do not impact system water efficiency, and therefore they fall outside the
purview of the WaterSense program.

This specification applies to POU systems only. EPA chose to exclude point-of-entry (POE)
systems from the scope of the specification because they treat—and subsequently waste—
much larger quantities of water than POU systems, and they are typically not recommended for
most treatment applications. While POE RO systems are generally more efficient due to their

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Reverse Osmosis Systems Supporting Statement

tendency to include electric booster pumps and/or recirculate some of the concentrate water,
not all end uses of water require or even benefit from the quality of water produced by an RO
system (e.g., water used for toilet flushes, clothes washing, or bathing). In most cases it is more
practical to install a POU system that treats water at just one fixture in a house than it is to
install a POE system to treat the entire household water supply. EPA, therefore, does not want
to encourage the use of oversized systems that subsequently generate significant water waste
during the treatment process. For the purposes of this specification, EPA is defining point-of-
entry RO systems as follows, based on the NSF/ANSI 330 definition for a point-of-entry system:

• Point-of-entry RO system: An RO system used to treat the water supply at the entry of
a building or facility for drinking and for washing, flushing, or other non-consumption use.
A POE RO system has a minimum initial clean-system flow rate of not less than 15 liters
per minute at 103 kilopascals pressure drop and 18 ± 5 °C water temperature (not less
than four gallons per minute at 15 psig pressure drop and 65 ± 10 °F water
temperature).

There are a variety of accessories or "add-on" devices available on the market intended to
improve water efficiency, enhance the production rate of treated water, or otherwise impact the
operation of an RO system. For example, a permeate pump is a non-electric device that can be
used to retrofit a POU RO system to reduce the back pressure from the storage tank and
therefore improve the system's water efficiency and performance. Other companion products
include retrofit recirculation kits (used to recirculate the concentrate water as feed water) and
any systems that divert RO reject water for other uses. This specification is intended to
recognize and label complete RO systems, not individual components (e.g., replacement
membranes), accessories, or other add-on devices. If a POU RO system requires the use of a
companion product to meet the requirements of the specification, then the companion product
must be tested, packaged, and sold along with the system in order for the system to earn the
WaterSense label.

General Requirements

NSF/ANSI 58 is the primary standard used in the United States to certify RO systems. This
WaterSense specification requires conformance with NSF/ANSI 58. This is consistent with
requirements for RO systems within the two primary model plumbing codes in the United States.

NSF/ANSI 58 prescribes testing procedures for measuring removal of total dissolved solids
(TDS) and requires all systems to reduce TDS by at least 75 percent. TDS, which includes
dissolved solids such as minerals, salts, metals, and organic matter in the water, is a common
indicator used to determine the general quality of drinking water. TDS percent reduction is a
performance metric that is used to quantify an RO system's ability to reduce drinking water
contaminants. By requiring all WaterSense labeled systems to be certified to NSF/ANSI 58, the
specification ensures that a baseline level of contaminant removal is achieved. The NSF/ANSI
58 standard also allows for and provides testing methods and requirements for the removal of
other more specific contaminants to verify manufacturer reduction claims. Systems are only
required to achieve specified removal rates for a given contaminant if the manufacturer makes a
claim that the system is able to reduce that contaminant. See the Performance Criteria section
for more information.

This specification also requires an RO system to be equipped with a shutoff device. ASSE 1086
includes a similar requirement and defines a shutoff device as a device that prevents reject

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water when the system is not treating water; EPA has adopted this definition for this
specification. Shutoff devices are especially important for preserving the water efficiency of RO
systems that have a tank. As the storage tank fills up, the pressure from the storage tank
increases and approaches the pressure of the incoming water. This is called "back pressure."1
An automatic shutoff valve is designed to automatically close when the back pressure from the
tank reaches a certain portion of the pressure of the incoming water. This stops the treatment
process and prevents the storage tank from overflowing, as well as treated water from flowing
down the drain. Inclusion of a shutoff device within RO systems is also required by the Uniform
Plumbing Code.

Water Efficiency Criteria

Water Efficiency Metrics and Test Procedures

NSF/ANSI 58 prescribes testing procedures for a system's water efficiency based on "efficiency
rating" and "recovery rating." These terms, further described below, are used to express the
percentage of intake water that ultimately becomes available to the user as permeate under
specific testing conditions. In general, systems with higher efficiency ratings or recovery ratings
are more water-efficient than those with lower ratings.

The specification requires all systems without a storage tank to have a minimum recovery rating
of 30 percent and all systems with a storage tank to have both a minimum recovery rating and
efficiency rating of 30 percent when tested in accordance with NSF/ANSI 58. While use of a
storage tank increases convenience and ensures that ample permeate is readily available to the
user, it also introduces back pressure that slows permeate production as the tank fills up. As a
result, the water efficiency for systems with a storage tank is lower than it would be if the system
did not have a tank. Therefore, separate water efficiency metrics and test procedures are
necessary for systems with a storage tank. The efficiency and recovery rating metrics, defined
below based on NSF/ANSI 58 and, by reference, NSF/ANSI 330, are meant to provide a more
comparable measure of efficiency for products with and without a storage tank, respectively.

•	Efficiency rating. The percentage of the influent water to the RO system that is
available to the user as treated water under operating conditions that approximate
typical usage. Only systems equipped with an automatic shutoff valve and a pressurized
or non-pressurized tank will have an efficiency rating.

•	Recovery rating. The percentage of the influent water to the membrane portion of the
system that is available to the user as RO treated water when the system is operated
without a storage tank, or when the storage tank is bypassed and the permeate is open
to the atmosphere. All products can have a recovery rating. Systems without a shutoff
valve and pressurize/non-pressurized tank will only have a recovery rating.

Systems without a storage tank will not have an efficiency rating. Therefore, the recovery rating
is used to quantify the system's water efficiency. Systems with a storage tank may have both a
recovery rating and an efficiency rating. However, the efficiency rating provides a more accurate
estimate that accounts for efficiency losses due to system backpressure. Based on a review of
certification data and product literature for systems currently available on the market, systems
with a storage tank are tested for both efficiency rating and recovery rating. Therefore,

1 Water Quality Association (WQA), 2019. "Getting Smart With Reverse Osmosis Systems: Best Practices
for Industry Professionals & Tips for Consumers." https://wqa.org/resources/getting-smart-with-reverse-
osmosis-systems/.

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WaterSense® Draft Specification for Point-of-Use
Reverse Osmosis Systems Supporting Statement

WaterSense

WaterSense intends to stay consistent with this practice and require all systems with a storage
tank to be tested and meet criteria for both efficiency rating and recovery rating. The efficiency
rating should always be lower than the recovery rating; therefore, as discussed in the Packaging
and Documentation Requirements section below, the efficiency rating will be used as the
primary water efficiency metric for tank systems.

More detailed test methods and calculations for efficiency rating and recovery rating are
included in NSF/ANSI 58. However, the general concept of the efficiency rating and recovery
rating can be understood by the formula below:

One important item to note is that some tankless systems on the market require a periodic
system flush in which water is passed through the treatment system and sent down the drain,
rather than being consumed, for a specified period of time. The NSF/ANSI 58 procedures do not
account for the volume of water used during this flush. Therefore, the recovery rating for
tankless systems with this feature may not convey the full the volume of wastewater (water not
available for end use) generated by these systems. EPA is aware of a current NSF task group
working to review and potentially revise the water efficiency testing procedures for NSF/ANSI 58
to account for this flushing procedure and develop a more accurate recovery rating value. The
task group that has undertaken this analysis is also evaluating whether it would be beneficial to
remove the term and concept of "recovery rating" from the standard and establish an industry-
wide practice of using one universal term to quantify and compare RO system water
efficiencies. The intent behind this change would be to reduce industry and consumer
confusion.

Because it is difficult to predict the timeline of any potential changes made to the standard
resulting from this task group, EPA has decided to move forward and develop a specification
that aligns with the current NSF/ANSI 58 standard. If the task group initiates any changes to the
standard that warrant revisions to the WaterSense specification prior to or following publication
of the final specification, EPA will evaluate the changes and revise the specification
requirements as necessary.

Water Efficiency Criteria

To establish the efficiency criteria, WaterSense reviewed NSF/ANSI 58 certification data from
the Water Quality Association (WQA), IAPMO R&T, and NSF. In its initial notification of intent to
develop a specification for this product category, WaterSense proposed a minimum efficiency
rating and recovery rating of 40 percent to align with the ASSE 1086 criteria. However, EPA
received substantial comments from stakeholders explaining that the 40 percent threshold is
difficult for many non-electric RO systems to achieve and would result in significant tradeoffs to
membrane life and removal rates for certain contaminants (e.g., nitrate/nitrite). Because
contaminant removal and membrane life are key performance metrics for RO systems, EPA
does not want to establish more stringent efficiency criteria that would compromise these
aspects of the system. This specification therefore establishes an efficiency threshold at 30
percent. EPA believes that this criterion balances water savings and market transformation
towards more efficient systems with potential performance tradeoffs and achievability across a
range of products.

Equation 1

percent recovery or
percent efficiency

permeate volume

* 100%

(concentrate volume + permeate volume)

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The 30 percent efficiency threshold also achieves the WaterSense program's goal of labeling
products that are at least 20 percent more water-efficient than typical products on the market.
As stated earlier, typical POU RO systems have an efficiency rating between 10 and 20 percent.
Assuming a 15 percent average efficiency rating and production of approximately 1,000 gallons
of permeate per year, a system would generate 5,667 gallons of reject water per year. This
reject water is typically disposed of as wastewater. By establishing criteria requiring RO systems
to achieve 30 percent efficiency, the amount of reject water generated would be reduced to
2,333 gallons per year, representing an average reduction in reject water of 59 percent and an
average reduction in overall system consumption by 50 percent. Even compared to a system
with a 20 percent efficiency rating, a WaterSense labeled system would reduce reject water by
42 percent and overall system consumption by 33 percent, as shown in Table 1.

Table 1. Waste Water Generated for Typical and WaterSense Labeled RO Systems

RO System Type

Gallons of
Permeate
Required per
Household per
Year

Efficiency Rating

Total Gallons Wasted
per Household per Year
(gallons)



A

B

C=(A/B)-A

10% efficient

1,000

10%

9,000

15% efficient

1,000

15%

5,667

20% efficient

1,000

20%

4,000

WaterSense labeled
RO system (30%
efficient)

1,000

30%

2,333

While many RO systems operate on water pressure alone, some systems use an electric pump
to feed incoming water through the treatment process. These systems tend to operate at higher
efficiency levels because the pump helps overcome backpressure from the storage tank. Both
pump-assisted and non-pump-assisted systems are included in the scope of the specification.
EPA considered setting different efficiency threshold requirements for pump-assisted and non-
pump-assisted systems. However, lack of data made it difficult to quantify the efficiency gains
attributable to electric pumps. Additionally, it is generally uncommon for WaterSense to specify
tiered water efficiency criteria based on product composition. Therefore, WaterSense has set
the efficiency and recovery rating requirements at threshold levels it understands to be
achievable with or without a pump. WaterSense considers electric pumps to be one of several
design strategies available to manufacturers to help them meet the specification requirements.

Performance Criteria

Based on industry research and discussions with stakeholders, EPA identified contaminant
reduction and membrane and filter lifespan as essential contributors to RO system performance.
From a consumer's perspective, the ideal RO system is able to substantially reduce drinking
water contaminants and is easy to maintain. These qualities provide convenience for the
consumer and assurance that their drinking water is adequately treated.

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WaterSense® Draft Specification for Point-of-Use
Reverse Osmosis Systems Supporting Statement

WaterSense

Membrane Life

As previously mentioned, there can be a tradeoff between RO system efficiency and membrane
lifespan, meaning that fouling of RO membranes may occur more frequently in more efficient
systems, which therefore requires more frequent membrane replacements. This can translate to
greater inconvenience and cost to the consumer. WaterSense addresses this tradeoff by
requiring systems to be tested according to the ASSE 1086 membrane life test—with
modification taking into consideration WaterSense's 30 percent efficiency criteria—and meet
certain efficiency, flow rate, and TDS removal criteria. The test must be performed over a
minimum of 20 days to produce a total product volume of at least 1,000 gallons. The procedure
calls for a difficult challenge water that places more stress on the membrane than typical tap
water. This test is meant to be representative of a year of treatment under challenge conditions.

WaterSense adopted the ASSE 1086 testing procedures to ensure that all labeled systems are
able to maintain adequate efficiency and performance for a minimum of one year under
challenge conditions. EPA considered increasing the test length and/or minimum treatment
volume to make the test representative of a longer period of use. However, because the test
uses a difficult challenge water, EPA believes the current requirements provide a reliable
benchmark upon which to measure membrane longevity. Systems that are able to achieve
these criteria will presumably last longer than one year in real-world applications with less
contaminated influent water.

The specification requires all systems to meet the following requirements upon completion of
the membrane life test:

•	The percent TDS reduction shall be a minimum of 75 percent each day.

•	The flow rate shall not decrease by more than 50 percent of the Day 1 reading
throughout the test.

•	The percent recovery, as calculated according to the ASSE 1086 testing procedures,
shall be on average a minimum of 30 percent. One-tenth of the sample readings may be
less than 30 percent and no less than 20 percent. The final percent recovery
measurement shall be at a minimum of 30 percent.

It is important to note that the percent recovery, as determined through the ASSE 1086
membrane life test, is not necessarily equivalent to the NSF/ANSI 58 recovery rating or
efficiency rating. In addition to differences in the makeup of the challenge water, under ASSE
1086, the percent recovery of all systems, regardless of whether they have a storage tank, is
measured using the following formula:

Contaminant Reduction Claims

Consistent with NSF/ANSI 58, the specification requires all manufacturer performance claims
for chemical reduction or mechanical filtration to be verified according to the applicable criteria
and requirements in NSF/ANSI 58. Rather than requiring that all products remove certain
contaminants, WaterSense chose to maintain the standard's structure of verifying the
manufacturer's contaminant removal claims. For each performance claim, the system must be

Equation 2

percent recovery =

100mL permeate

* 100%

(reject volume + 100 mL permeate)

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Reverse Osmosis Systems Supporting Statement

able to effectively reduce the level of the contaminant from the influent challenge level to less
than or equal to a set concentration for that contaminant outlined in the standard. This claim
reduction verification maintains maximum flexibility for manufacturers to make and market
products that target removal of certain contaminants, particularly in the event of a tradeoff in
performance associated with increased product efficiency and/or the removal of other
contaminants.

Packaging and Documentation Requirements

In addition to the applicable instructions and information requirements in NSF/ANSI 58, the
specification establishes packaging and documentation requirements to more clearly
communicate the water efficiency and performance of RO systems.

Water Efficiency Marking

This specification requires all WaterSense labeled RO systems to include on the packaging and
other point-of-purchase product documentation (e.g., product specification sheets, webpage) a
statement that clearly indicates the product's efficiency rating (for systems with a storage tank)
or recovery rating (for systems without a storage tank), along with the associated waste-to-
product ratio (i.e., the gallons of water the system will discharge for every gallon of treated water
it produces). The waste-to-product ratio is generally calculated from the efficiency/recovery
rating as show in Equation 3.

Equation 3

100%

waste-to-product ratio = Y.Y =		—-——	1

verified efficiency or recovery rating

For example, a system with a storage tank with a 30 percent efficiency rating would calculate
the waste-to-product ratio as follows:

100%

waste-to-product ratio = Y.Y =	1 = 2.3

F	30%

In this example, the RO system would send 2.3 gallons of water down the drain for every gallon
of permeate it produces and would include the resulting waste-to-product ratio (i.e., 2.3:1) on its
packaging and product documentation.

For RO systems, as the recovery or efficiency rating goes up, the waste-to-product ratio goes
down. Therefore, a lower waste-to-product ratio is indicative of a more water-efficient system.
EPA included this requirement so that customers can more easily comprehend and compare
efficiency and recovery ratings for labeled products and also understand how those ratings
translate to actual system water use and waste. NSF/ANSI 58 requires manufacturers to report
the system's verified efficiency rating in product instructions and on product data sheets
(recovery rating is optional). However, when researching products for this specification, EPA
identified several systems for which efficiency rating and/or recovery rating were not included in
product literature or where claims about efficiency in marketing materials did not appear to be
backed by the NSF/ANSI 58 certification data. Additionally, NSF/ANSI 58 does not specifically
require product packaging or point-of-purchase documentation (e.g., webpage listings) to
include this information, so it may not be available to potential buyers. Therefore, EPA is

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epa	WaterSense® Draft Specification for Point-of-Use

WaterSense	Reverse Osmosis Systems Supporting Statement

including this requirement to ensure that consistent information on system efficiency is available
and easy for customers to find and understand.

Contaminant Reduction Claim Marking

While this specification allows manufacturers continued flexibility to identify, through claim
verification, the specific contaminants the RO system can remove, EPA wants to make it easy
for the customer to determine whether a system is certified to reduce a certain subset of
drinking water contaminants that are of most common concern. Therefore, the WaterSense
specification requires all systems to include the following table on their product packaging and
associated point-of-purchase product documentation that clearly displays whether the RO
system has been verified to remove arsenic (pentavalent) challenged with an average
concentration of 300 parts per billion (ppb), chromium (hexavalent and trivalent), lead,
nitrate/nitrite, and perfluorooctanoic acid (PFOA)/perfluorooctane sulfonate (PFOS).

	Water Efficiency and Performance at a Glance	

	Water Use	

This system is certified to achieve a XX% [efficiency rating/recovery
rating] in the production of treated water. This means that it will send
Y.Y gallons of water down the drain for every gallon of treated water

it produces.	

Contaminant Removal

Contaminant

NSF 58 Minimum
Required Reduction

Actual Reduction

Arsenic1

96.7%

% Removal/Not Tested

Chromium2

66.7%

% Removal/Not Tested

Lead

96.7%

% Removal/Not Tested

Nitrate/nitrite

66.7%

% Removal/Not Tested

PFOA/PFOS3

95.3%

% Removal/Not Tested

•	All contaminant removal claims listed above are verified through
NSF/ANSI 58 testing

•	Contaminants listed as "Not tested" have not been verified for
removal under NSF/ANSI 58

•	All contaminants reduced by this system are listed in the
performance data sheet

•	Not all contaminants listed may be present in the water	

1	Pentavalent, at a concentration of 300 parts per billion (ppb)

2	Hexavalent and trivalent

3	Perfluorooctanoic acid/perfluorooctane sulfonate	

WaterSense consulted with the EPA Office of Ground Water and Drinking Water to identify this
subset of priority drinking water contaminants for RO system consumers. Per NSF/ANSI 58 and
this WaterSense specification, a product is only required to be tested for removal of these
contaminants (among others) and meet minimum reduction requirements if the manufacturer
advertises a reduction claim for those contaminants.

EPA also intends for the label able to help small public water systems (PWSs) identify more
efficient products that can be used to treat for target contaminants of concern in their water
supply. Wth the approval from the primacy agency, EPA allows small PWSs to use point-of-use

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RO systems or other treatment technologies to meet the requirements of the National Primary
Drinking Water Regulations (NPDWRs) as these systems may be a more affordable option for
PWSs than traditional, centralized treatment. The EPA document, Point-of-Use and Point-of-
Entry Treatment Options for Small Drinking Water Systems, provides guidance on this
compliance option. California adopted a similar regulation allowing PWSs with less than 200
service connections to use point-of-use treatment systems to fulfill the requirements of the Safe
Drinking Water Act where centralized treatment is not immediately economically feasible.

Replacement Parts and Operation and Maintenance Marking

Consistent with NSF/ANSI 58, the specification also requires that product literature (e.g.,
manuals, installation and maintenance instructions) include information on replacement parts for
membranes, filters, and any other components that are expected to require replacement during
the life of the system. The literature should also state the recommended replacement frequency
for each component. Proper maintenance is essential to the performance and water efficiency of
the system, and failure to replace these components could lead to the system no longer meeting
the specification criteria. Therefore, it is important that the consumer understand their role in
maintaining the system. Additionally, this specification requires that any instructions related to
the maintenance of the product direct the user on how to maintain product efficiency. The
product packaging, marking, and literature may not include instructions directing the user to an
operational setting that would override the system's efficiency.

If a system requires the use of components or a companion product (e.g., permeate pump) to
meet the requirements of the specification, this specification requires that these components
and/or companion products be packaged and sold along with the system in order to bear the
WaterSense label.

IV. Potential Savings and Cost Effectiveness
Potential Water Savings

The ASSE 1086 testing protocol, which is meant to be representative of a year's water
consumption in a typical home, requires the system to produce a minimum product volume of
1,000 gallons of treated water. WaterSense assumes that the average person will withdraw one
gallon of permeate per day from their RO system for drinking and cooking. According to the U.S.
Census Bureau, the average number of persons per household is 2.6.2 This translates to
approximately 950 gallons of water per household per year for drinking and cooking, which
aligns approximately with the ASSE 1086 estimate of 1,000 gallons per year. As mentioned
previously, WaterSense identified typical efficiency ratings between 10 percent and 20 percent
for RO systems with storage tanks (common in residential settings). Therefore, WaterSense is
assuming an average efficiency rating of 15 percent for typical POU RO systems. As shown in
Table 2 on page 12, this translates to 5,400 gallons of waste water sent down the drain per
household per year. A WaterSense labeled RO system with an efficiency rating of 30 percent
will send just 2,220 gallons of waste water down the drain per year to produce the same amount
of treated water. This means a household will save an estimated 3,180 gallons of water per year
when switching to a WaterSense labeled RO system.

2 U.S. Census Bureau, 2020. American Community Survey. Table S1101. Households and Families.

https://data. census. gov/cedsci/table?q=Families%20and%20Household%20Characteristics&tid=ACSST5Y2020.S11

01

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WaterSense® Draft Specification for Point-of-Use
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Table 2. Water Savings Potential for WaterSense Labeled POU RO Systems







Gallons of











Permeate





System
Type

Consumption
(gallons) per
Person per
Day

Persons
per
Household

Required

per
Household
per Year

Efficiency
Rating

Total Concentrate
Generated per
Household per
Year (gallons)



A

B

C=A*B*365

D

E=(C/D)-C

Typical RO
system







15 percent

5,400

WaterSense
Labeled RO

1

2.6

953

30 percent

2,220

system











Water Savings per Year (Gallons)

3,180

EPA estimates that one million new RO systems are installed in the United States each year,
either for new sales or natural replacement. If all new units were WaterSense labeled, more
than three billion gallons of water could be saved annually across the country.

Cost Effectiveness

According to the American Water Works Association (AWWA) 2021 Water and Wastewater
Rate Survey, the average combined estimated cost of water and wastewater for residential
customers in the United States is $13.11 per thousand gallons.3 Therefore, households that use
a WaterSense labeled RO system instead of an RO system with typical efficiency can expect to
save approximately $40 per year on water and wastewater expenses.

It is difficult to quantify the cost and potential payback of a WaterSense labeled RO system
compared to a typical RO system because the cost and lifespans of systems, membranes, and
filters vary substantially across the market and are affected by factors other than water
efficiency. RO systems range from about $180 to upwards of $700. Anecdotally, EPA has
observed that more efficient RO systems tend to be in the middle or on the higher end of this
range. However, this could be due to the inclusion of more expensive parts, such as electric
pumps, that aren't necessarily designed or incorporated to increase water efficiency, but
nonetheless improve it. Due to the lack of data to distinguish the impact water efficiency has on
system and maintenance costs, EPA cannot provide an accurate estimate of the payback period
of a WaterSense labeled RO system.

Replacement membranes can cost between $20 to $100, similarly dependent on the model and
manufacturer. Based on discussions with manufacturers and industry stakeholders, the primary
impact of water efficiency on RO system cost is attributed to potential increases in membrane
replacement frequency—membranes in higher efficiency systems may foul more quickly and
therefore require more frequent replacement. The membrane life test requirement included in
the specification is meant to ensure that the membrane will last at least one year; however, as
discussed in the Performance Criteria section, EPA anticipates membranes able to meet the
testing requirements under challenge conditions will last longer. This requirement is intended to
protect against significant increases in maintenance costs due to purchase of replacement

3 Raftelis Financial Consulting, Inc. American Waterworks Association. 2021 Water and Wastewater Rate Survey.

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membranes. Additionally, annual water and wastewater cost savings can help offset additional
costs from membrane replacement.

V. Certification and Labeling

WaterSense has established an independent, third-party product certification process,
described in the WaterSense Product Certification System. Under this process, products are
certified to conform to applicable WaterSense specifications by accredited licensed certifying
bodies. Manufacturers are authorized by licensed certifying bodies to use the WaterSense label
in conjunction with labeled products.

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