WaterSense® Guide to Selecting
Water Treatment Systems

November 2024

WaterSense


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WaterSense Guide to Selecting Water Treatment Systems

Introduction

It is not unusualforwaterto contain some contaminants
or impurities. Your water system treats water to remove
contaminants, and under the Safe Drinking Water Act
(SDWA), the U.S. Environmental Protection Agency (EPA) sets
legal limits on more than 90 contaminants in drinking water.

These legal limits are intended to protect human health by
establishingthe maximum amount of each contaminant that
can be present in drinking water. U.S. water utilities provide
treated drinking water that meets these standards and are
otherwise required to communicate when unsafe levels of
contaminants are present. However, if you are concerned
with the taste, odor, color, or potentially unhealthy
concentrations of contaminants in your drinking water at home or at work, water treatment units can be
used to improve water quality. EPA's WaterSense program has developed this guide to help consumers
understand treatment options for drinking water and how these systems can be maintained to ensure
good performance and water efficiency.

Understanding Your Water Quality

Homes and businesses that get their water from a public water system should receive a consumer
confidence report (CCR) from their utility each summer. The CCR contains state-certified lab results that
compare the utility's water quality against National Primary Drinking Water regulations. As a water utility
customer, you have the right to review the CCR; contact your local water supplier if you have not received
one. Learn more about CCRs on EPA's website at www.epa.gov/ccr/ccr-information-consumers.

Homes that receive water from a well should have their water periodically tested by a state-certified lab
to assure compliance with national drinking water standards. Individuals who receive water from a public
utility but are concerned about their water quality can also get their water tested by a state-certified
lab. EPA maintains a list of certified laboratories atwww.epa.gov/dwlabcert/contact-information-
certification-programs-and-certified-laboratories-drinking-water. EPA also has information about what to
do to safeguard and test well water atwww.epa.gov/privatewells/protect-your-homes-water.

Determining Your Treatment Goals

Using water quality test results, CCR information, and/or personal experiences with the water supply,
you can determine whether your water quality poses any concerns that need to be addressed, if there are
specific contaminants or concerns, you may wish to purchase a water treatment unit, but it's important
to identify your treatment goals first. Table 1 on page 3 describes some example water treatment
goals and potential sources of contamination. For additional information on a wide variety of water
contaminants, visit EPA's National Primary Drinking Water Regulations web page: www.epa.gov/ground-
water-and-drinking-water/national-primary-drinking-water-regulations.

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WaterSense Guide to Selecting Water Treatment Systems

TABLE 1: EXAMPLE WATER TREAMENT GOALS AND CONSIDERATIONS

Example
Treatment
Objective

Potential Sources of
Contamination

Highest
Susceptibility

Potential Health Effects

Improve taste and
odor

Disinfectants
and minerals in
municipally-supplied
water

Municipally-supplied
water

Taste and smell are not necessarily a
sign of poor water quality, since most
harmful contaminants do not affect the
taste or smell of water. Consider having
water tested or consult the local water
utility if there are noticeable changes in
taste or smell.

Remove lead

Corrosion in lead
service lines and lead-
soldered plumbing
parts

Homes and
businesses with lead
service lines

Lead in drinking water is especially
harmful to children and pregnant
women; it can cause damage to the
brain and nervous system, impede
development, and introduce learning,
behavior, hearing, and speech issues in
children.

Remove nitrate

Fertilizer, manure,
septic systems, and
sewage, as well as
natural deposits

Well water

Nitrate can decrease blood's ability to
carry oxygen to tissues, which can most
severely affect pregnant women and
bottle-fed babies.

Remove arsenic

Found naturally in
some groundwater

Private wells and
public water systems
that use groundwater

Arsenic has been linked to several
cancers and can cause other symptoms
such as nausea, decreased production
of red and white blood cells, and
abnormal heart rhythm.

Remove per- and
polyfluoroalkyl
substances
(PFAS)

Industrial sites (e.g.,
textile and plastic
manufacturers),
landfills, fire training
and fire response sites

Water sourced
near urban areas
and potential PFAS
sources

Studies have shown that PFAS could be
linked to several cancers, liver damage,
high cholesterol, and increased risk of
asthma.

Why Does My Water Smell Like a Swimming Pool?

Sometimes you may smell chlorine in your tap water because your utility adds chlorine as part of the
water treatment process. Chlorine is a disinfectant used to help to control pathogens in water. Many
treatment devices can remove chlorine to improve water taste and odor. When selecting a treatment
device, make sure to choose one that has been certified to NSF International (NSF)/American
National Standards Institute (ANSI) 42 Drinking Water Treatment Units—Aesthetic Effects. The NSF/
ANSI 42 standard addresses products that improve taste and odor. You can also reduce the chlorine
taste and odor by simply pouring water into an open pitcher and placing it in the refrigerator for a
day or two. The chlorine will naturally evaporate from the water over time, reducing taste and odor
concerns.

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WaterSense Guide to Selecting Water Treatment Systems

Certain individuals may not be concerned with removing a particular contaminant but instead wish
to protect vulnerable populations in their household (e.g., pregnant women, children, the elderly,
immunocompromised) who may be more susceptible to waterborne pathogens. In these cases, ensuring
removal of pathogens, such as Cryptosporidium, Giardia, and E. coli, may be of particular concern.
However, conventional water treatment processes are highly successful at pathogen removal in drinking
water.

Why Soften Water?

Water hardness increases with calcium and magnesium
concentrations. Homes and businesses with significant water
hardness may see mineral/scale formation on plumbing fixtures
and appliances and find it difficult to get sufficient lather from
soaps and detergents. While some water hardness is generally not
a health hazard, water softeners can be used to remove excessive
hardness.

Softening water with a water softener or neutralizing the scale-
forming water properties using a water conditioner can improve
taste and reduce impacts of water hardness on the plumbing
system. When selecting a water softener or conditioner, make
sure to choose one that has been certified to NSF/ANSI44 Requirements for Water Softeners or
International Association of Plumbing and Mechanical Officials (IAPMO)/ANSI Z601 Standard for
Scale Reduction Devices.

Cation exchange water softeners can consume water during ion regeneration cycles and can
therefore contribute to additional water use. NSF/ANSI 44 includes a voluntary efficiency rating that
requires softeners to use 5.0 gallons of water or fewer per 1,000 grains of hardness removed. To
minimize water and salt use when selecting a water softener, identify a model with demand-initiated
regeneration that has a lower water consumption (i.e., gallons per 1,000 grains of hardness removed)
and higher salt efficiency (i.e., grains of hardness exchanged per pound of salt).

Cation exchange water softeners can impact local water quality because they discharge salts as part
of the treatment process. Therefore, some local jurisdictions have restrictions on the installation and
use of these systems. Check local requirements prior to purchasing one of these systems.

Deciding What Is the Right System for Your Needs

Once you have identified water treatment goals for your situation and reviewed the options, you can
select a system that fits your water use and lifestyle. Think about where treated water is needed most
at home or in your business and the quantity of water that requires treatment each day. Avoid oversizing
treatment systems, as larger systems tend to be more costly to purchase, operate, and maintain. Note,
many water-consuming activities within a home or business (e.g., f lushing toilets, washing clothes) do
not require additional water treatment; stick to only treating water used for cooking and drinking.

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WaterSense Guide to Selecting Water Treatment Systems

Point-of-Use Systems

Treating water at the tap or where it is used is known as point-of-use treatment and can include a water
pitcher with a filter; a filter that is installed on a dedicated faucet or spigot; or a device installed under
the sink. Point-of-use devices are best suited for homes or businesses that wish to treat water used for
drinking and cooking. Following are some point-of-use systems and how they are used:



Less





Costly











More





•	Water pitcher filters depend on the user to fill the pitcher with water manually.

•	Faucet-mounted filters are attached to existing faucets and can be toggled on
and off to produce filtered or unfiltered water from the tap.

•	Refrigerator filters are a built-in feature of many modern refrigerators. Water
and ice are supplied through a dedicated spigot or dispenser. Filters should be
replaced based on the manufacturer's instructions.

•	Faucet-integrated filters are faucets equipped with integrated filters. The filter
housing is built into the faucet rather than a separate filter fitted to the tap.

•	Countertop or stand-alone systems can be placed away from the kitchen sink
and either draw water from the water supply line or require water to be filled
manually within a self-contained unit.

•	Under-sink systems are typically installed under the kitchen sink and are
plumbed into a seperate faucet. Water from the supply line is treated within the
system before it is directed to a dedicated faucet. Under-sink systems can treat
larger quantities of water.

Point-of-Entry Systems

A point-of-entry—or whole-house—system is installed to treat water at the point the water enters the
building to distribute treated water throughout it for all uses (e.g., toilet flushing, showering, clothes
washing). Therefore, point-of-entry devices treat large quantities of water, and they are best suited
for situations where the water source poses consistent and significant contamination challenges.
Installation of these systems generally costs several thousand dollars and may require plumbing
alterations and professional maintenance services.

Figure 1. Types of Water Treatment Systems

To Irrigation
System

Point
of Use

System

Point of Entry (POE) Treatment

Point of Use (POU) Treatment

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WaterSense Guide to Selecting Water Treatment Systems

Water Treatment Technologies

Water treatment technologies vary by levels of contaminant removal and sophistication, so consideryour treatment goals when reviewing
options. Table 2 describes typical residential and commercial facility water treatment technologies and their testing standards, benefits,
and limitations. Table 2 also shows whether a treatment technology consumes additional water during the treatment process. Several
water treatment systems are available, and no single treatment system removes all contaminants, but many systems combine treatment
technologies to address a wide range of water concerns.

TABLE 2: WATER TREATMENT TECHNOLOGIES COMPARISON

Treatment
Technology

A	Does It Consume

How It Works	pp ica e es ing	Benefits	Limitations	Water During

Standard	T ^ °

Treatment?

Filtration

Filters often use physical
barriers, such as fabric,
fiber, ceramic screening,
or other filtration methods
to remove contaminants.
Activated carbon or resins
are commonly used in filters
to trap contaminants and
improve taste and odor.

•	NSF/ANSI 42: Drinking
Water Treatment
Units—Aesthetic
Effects

•	NSF/ANSI 53: Drinking
Water Treatment
Units—Health Effects

•	NSF/ANSI 401:
Emerging Compounds/
Incidental
Contaminants

•	Relatively inexpensive
to install and maintain

•	Improves taste and
odor

•	Removes organic
contaminants

•	Some can remove
chlorination
byproducts, cleaning
solvents, and
pesticides

• Does not remove
nitrates, bacteria, or
dissolved minerals

No

Reverse
Osmosis
(RO)

Using pressure, RO
forces water through a
membrane that limits the
size of the particles that
can pass through. The
membrane traps and rejects
contaminants, creating a
stream of treated water that
is able to pass through the
membrane and a stream of
reject water that is unable to
pass through the membrane.

NSF/ANSI 58: Reverse
Osmosis Drinking Water
Treatment Systems

•	Improves taste and
odor

•	Removes sodium,
dissolved inorganics,
and organics

•	Some can reduce
nitrates, pesticides,
dioxins, chloroform,
and petrochemicals

•	Does not remove all
inorganic and organic
contaminants

•	Removes beneficial
minerals such as
calcium, along with
contaminants

•	Can be costly to install
and maintain

Potentially produces
a large quantity of
reject water during
the treatment
process; select a
WaterSense labeled
RO system to waste
less water

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Treatment
Technology

How It Works

Applicable Testing
Standard

Distillation

Water is heated to the boiling
point to kill microbes and
generate water vapor. Most
chemical contaminants
remain in the liquid water.
The water vapor is then
collected into a separate
container as it condenses.

NSF/ANSI 62: Drinking
Water Distillation
Systems

Ultraviolet
(UV)

Water is passed through a
chamber equipped with a
UV lamp that is used to kill
pathogens.

NSF/ANSI 55: UV Water
Treatment Systems

WaterSense Guide to Selecting Water Treatment Systems

Benefits

•	Removes nitrates,
bacteria, viruses,
pathogens, sodium,
hardness, dissolved
solids, most organic
compounds,
heavy metals, and
radionuclides

•	Can be used during boil
water advisories

Inactivate biological
contaminants such as
bacteria, viruses, and
protozoa

Limitations

•	Does not remove
some volatile organic
compounds, some
pesticides, or volatile
solvents

•	Bacteria may grow on
cooling coils during
inactive periods

•	Can be costly, and
treatment is typically
energy-intensive

•	Not effective against
chemicals (e.g., heavy
metals, organics)

Does It Consume
Water During
Treatment?

Minimal water
consumption
for cleaning and
maintenance
between uses

No

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WaterSense Guide to Selecting Water Treatment Systems

Water Treatment Technology Certification

Certification of water treatment products
helps ensure that the manufacturers' claims
are independently verified and accurate.

When choosing treatment technologies, it is
important to ensure that they are certified to
the applicable NSF/ANSI standards to treat for
targeted contaminants. Certifications focus
on different contaminants and performance
indicators, and the specific contaminants
that each treatment system can treat for can
vary widely. Some systems combine different
technologies to treat a variety of contaminants
and are therefore certified to multiple
standards. For example, an RO system might
include filters or UV treatment in addition to the
RO membrane, and therefore could be certified
to NSF/ANSI 42, NSF/ANSI 53, or NSF/ANSI 55,
in addition to NSF/ANSI 58.

Figure 2: Example Certification Marks on Water Treatment
Products

NSF/ANSI 42 & NSF/ANSI 372 Certified

Ensures your drinking water safety

Lead free



Certifi&L- JV WQA again . NSF/ANSI standard 42 m model EWF-8000S loi

tlie reduction ot the claims specified on the Performance Eata Sheet and to
NSF/ANSI 372 (50.25% lead).

Toted and certified by WQA International oyoinsi NSF/ANSI 42, and NSF/ANSI 372 standard*.

Look for the certification logos on the product
packaging, supporting documentation, and/
or the system itself, or language to suggest
the system is certified to the applicable
standard (Figure 2). In addition, review
the system's performance data sheet to
confirm it is certified to treat for the targeted
contaminant(s), or check for listings on a
third-party certification website. Third-party
certification is offered by organizations such as
CSA Group, ICC Evaluation Services (ICC-ES),
IAPMO Research and Testing (R&T), NSF, UL,
and the Water Quality Association (WQA).

Pricing and Water Efficiency

Prices of water treatment systems and
installation vary depending on the type of
technology used, where the unit is installed,
and what contaminants it removes. Basic
water pitchers and tap filters typically cost
less than $100 and require no installation,

Look for the WaterSense Label

Reverse osmosis systems
generate water waste during
the treatment process and
therefore, will increase home
or building water use once
installed. EPA estimates that a
typical point-of-use RO system generates at least
five gallons of water waste for every gallon of
treated water it produces, while some inefficient
models can consume up to 10 gallons of water
waste for every gallon of treated water produced.

All RO systems will generate some water waste.
If purchasing an RO system, be sure to select a
WaterSense labeled RO system for a more water-
efficient option. WaterSense labeled models
generate 2.3 gallons of water waste or less for
every gallon of treated water produced. For more
information, visitwww.epa.gov/watersense/point-
use-reverse-osmosis-systems.

A "•

& ™ Jy

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WaterSense Guide to Selecting Water Treatment Systems

whereas distillation and RO systems tend to cost a few hundred dollars and may require professional
installation, Point-of-entry systems can cost thousands of dollars and generally require professional
installation. Maintenance costs for all types of systems typically include periodic filter and/or membrane
replacements to ensure the treatment is occurring.

A system's efficiency can also affect the long-term cost of a water treatment option. For example, RO
systems increase overall household or building water use, because they generate water waste for every
gallon of treated water produced. Distillation, meanwhile, is an energy-intensive process that can
increase your energy bill.

Maintenance

All water treatment systems require some level of ongoing
maintenance to ensure they remain effective and efficient,
and unmaintained systems may make water quality worse.

Maintenance may involve changing filters, disinfecting treatment
units, removing mineral build-up, and backwashing. Filters
should be replaced accordingto the manufacturer's instructions
and recommended schedule. Some systems, such as RO
systems, also have a membrane and other parts that may need
to be replaced over time. Periodic water testing using a home
test kit can help ensure that systems are functioning properly.

Some purchasers may opt to have their system professionally
maintained. Several companies offer maintenance services that send a water treatment professional to
your home regularly to replace filters, clean your system, and address any specific concerns.

References and Additional Resources

CDC. About Choosing Home Water Filters, https://www.cdc.gov/drinking-water/prevention/about-choosing-home-water-
filters.html.

CDC. About Home Water Treatment Systems, https://www.cdc.gov/drinking-water/about/about-home-water-treatment-
systems.html.

EPA, 2024. Consumer Tool for Identifying Point-of-Use and Pitcher Filters Certified to Reduce Lead in Drinking Water, https://
www.epa.gov/system/files/documents/2024-06/how-to-id-filters-certified-to-reduce-lead-in-drinking-water-epa june-2024.
pdf.

EPA, 2024. Reducing PFAS in Your Drinking Water with a Home Filter, https://www.epa.gov/system/files/documents/2024-04/
water-filter-fact-sheet.pdf.

EPA, 2006. Point-of-Use or Point-of-Entry Treatment Options for Small Drinking Water Systems, https://www.epa.gov/sites/
defauLt/fiLes/2015-09/documents/guide smaLLsystems pou-poe june6-2006.pdf.

EPA. Drinking Water in Your Home, www.epa.gov/ground-water-and-drinking-water/drinking-water-your-home.

EPA WaterSense. Point-of-Use Reverse Osmosis Systems, www.epa.gov/watersense/point-use-reverse-osmosis-systems.

Minnesota Department of Health, 2022. Home Water Treatment Fact Sheet, www.health.state.mn.us/communities/
environment/water/factsheet/hometreatment.html.

oEPA

To learn more about WaterSense, visitwww.epa.gov/watersense.

(866) WTR-SENS (987-7367) j watersense@epa.gov	832-F-24-024

November 2024


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