Pool Water Efciency
JUMP Into
Thoughtful residential swimming pool design and ongoing maintenance can
help save pool owners water, energy, and money. Addressing issues related
to evaporation, water quality, leaks, or pool usage can all save water. The U.S.
Environmental Protection Agency’s (EPA’s) WaterSense
®
program developed
this guide to help residential pool owners and maintenance professionals
understand and minimize pool water use. Commercial pool owners can nd
additional information in WaterSense at Work: Best Management Practices for
Commercial and Institutional Facilities at www.epa.gov/watersense.
Introduction
Pools provide a fun and relaxing way to keep
cool during warmer months. However, if not
adequately maintained, your pool could be
sending water and money down the drain.
Pools can consume water through evaporation,
pool cleaning, leaks, and splashing. Investing
in new equipment or employing targeted
maintenance techniques can save water,
energy (for heated pools), and money.
This guide provides an overview of design
considerations, retrots, and maintenance
practices that are aimed to improve the water
eciency of residential pools. WaterSense
developed this guide with a focus on in-
ground and above-ground residential
pools, but many of the practices also apply
to commercial pools or spas. For more
information, consult the additional resources
listed at the end of this document.
Evaporation
Evaporation is one of the leading causes of
water loss in residential pools, especially in hot,
drier climates where pools are most prevalent.
The rate of evaporation from a pool is
dependent on a number of variables, including
temperature, humidity, and wind speed. EPA
estimates that, depending on climate, an
uncovered 500-square-foot swimming pool
could lose between 12,000 and 31,000 gallons
of water per year due to evaporation, with this
number being even higher for heated pools.
Not only does this contribute to water waste,
but it can also cost homeowners money!
Reducing water loss from evaporation is the
best way to reduce overall water usage in your
pool.
Size Pools for Use
A pool’s surface area directly impacts the
volume of evaporation that may occur. In
eect, the larger a pool, the more water that
is likely to be lost due to evaporation. Further,
a deeper pool requires more water to ll and
more resources to maintain (e.g., ltration,
chemicals, heating).
Therefore, when planning a new pool
installation, consider how you want to use the
pool and select a size and design that will meet
your needs while minimizing potential water
usage. A smaller pool design can result in lower
maintenance costs and helps reduce water
consumption.
Cover Up
Pool covers are the most eective method
of reducing water losses from evaporation.
When in use, solid pool covers can reduce
evaporation by more than 90 percent and, in
the case of heated pools, save between 50 and
70 percent of pool heating costs.
1
Any pool can
Cover Your Bases
According to data collected as part of
the 2016 Residential End Uses of Water
study, only 15 percent of pool owners
have and regularly use a pool cover.
2
1
Minos, 2021
2
DeOreo et. al., 2016
2
3
Table 1: Types of Pool Covers and Their Attributes
Type
Eectiveness
at Reducing
Evaporation
When in Use
3
Can It Serve
as a Safety
Cover?
Additional Information and
Considerations
Solid/mesh/hybrid Up to 95 percent Yes
Mesh covers are lighter weight
than solid covers but allow more
evaporation to occur.
Solar (bubble cover,
solar rings, thermal)
50 to 95 percent
(varies based
on shape and
coverage)
No
Solar covers are designed to use
the sun’s energy to heat the pool.
Liquid evaporation
suppressant
15 percent No
Non-toxic, chemical evaporation
suppressant is applied to pool
surface on a regular basis.
3
Muleta, 2016
Figure 1: Solid Pool Cover
Figure 3: Reel Used For Applying Bubble
Pool Cover
Figure 4: Solar Rings
3
Figure 2: Bubble Pool Cover
be retrotted with a cover, so if your pool
doesn’t have one, this is the most eective rst
step you can take to reduce evaporation. If you
already own a cover, use it as often as possible,
as covers are only eective at reducing
evaporation when they are applied.
Pool covers can be made from a variety of
materials and can signicantly vary in terms
of cost, usability, safety, and eciency. Solid
covers prevent debris and precipitation from
entering the pool, but water can collect on top,
which may require a pump to remove. Mesh
covers allow some debris and precipitation to
pass through, so no water will collect on top.
Table 1 on page 3 displays the most common
types of pool covers on the market and their
associated attributes.
Pool covers are only eective when applied to
the surface of the pool; therefore, pool owners
should consider ease of use when making a
purchase so that any time the pool is not in
use, the pool cover is. Automatic covers, which
are installed on a track at the edge of your pool,
can be deployed at the press of a button and
can take the heavy lifting out of pool cover
use. If an automatic pool cover is not practical,
a motor-driven reel or hand crank can be used
with some types of covers to help guide the
cover over the pool surface.
Winter covers are a subset of pool covers. A
winter cover is used over an extended period
during the pool oseason to protect it from
damage and debris. Winter covers can be more
secure and typically double as safety covers,
but often are not practical to be used on a daily
basis for evaporation reduction.
Some utilities oer rebates of up to $200 for
qualied covers. Check with your local water
utility to see if they oer a rebate to purchase
and install a pool cover.
Cool O
Water temperature aects the evaporation
rate of a pool, since higher temperature water
evaporates more quickly. In a heated pool,
evaporation reduces the water temperature,
which means additional energy is needed to
keep the pool at the desired temperature. Most
heated pools are kept between 78°F and 82°F,
and depending on your location, each degree
increase could increase energy costs by 10
to 30 percent.
4
For an outdoor pool, keeping
the pool temperature lower can reduce
evaporation and heating costs. For an indoor
pool, keeping the ambient air temperature
higher than the water temperature can reduce
evaporation. If you are planning to be away for
several days, be sure to turn the pool heater o
or turn the temperature down. Don’t forget to
throw on a pool cover, too!
Other Ways to Reduce Evaporation
Many pools have water features such as
fountains or waterfalls. While these features can
4
Minos, 2021
4
Safety First
When purchasing a cover for your
pool, prioritize safety, in addition
to potential water and energy
savings. Safety covers help inhibit
pool access by children, animals, or
other unwanted swimmers during
unsupervised periods.
Pool covers can be certied as
safety covers under ASTM F1346-
91, the Standard Performance
Specication for Safety Covers and
Labeling Requirements for All Covers
for Swimming Pools, Spas and Hot
Tubs. The standard test methodology
includes tests for load bearing and
surface water drainage, and also
ensures no openings are present
between the cover and pool. Many
states and local jurisdictions have
established safety requirements for
residential pools, and in some cases
require a safety cover if fencing and
locked gates are not installed.
5
be aesthetically pleasing when the pool is in
use, the turbulence added to the pool surface
increases evaporation and can also result in
water lost to wind or splashing. To reduce
water loss, only turn on these features when
the pool is in use. Alternatively, put water
features on a timer to make sure they turn o
after a set amount of time or at night.
Installing a windbreak to reduce wind speed
around the pool can also help to reduce
evaporation. Landscaping or other physical
barriers, such as stone walls or fencing, can
increase wind protection. Increasing shade
through landscaping can also keep the pool
cooler and reduce the eects of evaporation.
Be sure to carefully select landscape plants so
they don’t contribute more debris to the pool.
Water Quality
Maintaining a pool’s water quality keeps water
safe and looking clean for swimmers, but it
can also reduce water loss! The California
Urban Water Conservation Council (CUWCC)
estimated that 23 percent of quantiable pool
water use is attributed to lter backwashes,
the process of sending water backwards
through a lter to remove debris build-up,
and 21 percent is attributed to control of
total dissolved solids (TDS), which can only
be maintained by dumping portions of
contaminated water and replacing it with
fresh water.
5
Keeping a pool free of debris
and microbes can reduce corrosion, decrease
the risk of developing leaks, and increase the
longevity of your pool water.
Filtration
Deploying a high-performance lter can
keep debris out of a pool and reduce the risk
of leaks. Filters range in their ltration ability
5
Koeller and Homan & Associates, 2010
6
ENERGY STAR, n.d.
Pump It Up
Pool pump upgrades can make your
circulation system energy-ecient
and extend the life of your pool lter.
Beginning in 2021, pool pumps sold
in the United States are required to
be variable-speed pumps. A variable-
speed pump oers substantial energy
savings compared to older models.
ENERGY STAR
®
certied pool pumps
take energy eciency even further,
reducing energy use by 11 to 18
percent.
6
(measured in terms of the smallest particle they
can lter out); cost; maintenance practices; and
water eciency. Filtration ability is discussed in
terms of microns (one micron is one millionth
of a meter). The smaller the micron that can be
removed, the better the ltration ability. Table
2 displays the main types of pool lters on the
market and their associated characteristics.
Each lter type has its advantages and
disadvantages. Sand lters are the most
commonly used lter type for residential
pools due to lower initial cost and ease of
maintenance. A comparable, but more water-
ecient, alternative to sand lters is a lter
with glass media, which allows a shorter
backwash cycle. Glass media can often be
used as replacement media within an existing
sand lter. Cartridge lters are the most
water-ecient because they do not require
backwashing. Using oversized cartridge lters
can also cut down on water use because
cleaning frequency is reduced. Diatomaceous
Earth (DE) lters oer the highest performance
but are also the most costly and require
additional DE after each backwash.
6
7
Koeller and Homan & Associates, 2010
8
Giovanisci, 2021
9
1
st
Direct Pools, 2021
10
DOE, n.d.
Heat Up Energy Savings
Take energy eciency into
consideration when purchasing a new
pool heater. Consider replacing your
gas heater with a solar heater or heat
pump to reduce long-term energy
costs.
If purchasing a heat pump pool
heater, check its coecient of
performance (COP) to determine the
energy eciency. COPs typically range
from 3 to 7; the higher the COP, the
more ecient the heater.
10
Check the DOE’s Energy Saver pages
on ecient pool heaters for more
information.
Table 2: Types of Filters and Their Attributes
Filter Type Filtration Ability
Water
Usage
Filter Media
Lifetime
Maintenance Practices
and Other Notes
Sand 20 - 40 microns
7
3 - 6 years
7
• Backwash once per week
Glass 5
microns
8
7 - 15 years
9
• Backwash once per week
• Alternative to sand with
shorter backwash cycles
• Requires less frequent
replacement of media
than sand lters
Diatomaceous
Earth (DE)
5 microns
7
2 to 3 years
(grid lifetime)
8
• Backwash every 4 to 8
weeks
• DE media must be
added after every
backwash
• DE can be harmful if
inhaled
Cartridge
10 microns
(can vary)
7
2 to 4 years
7
• Frequency of cleaning
depends on cartridge
• Clean by spraying with
hose, no backwash
required
7
If you are constructing a new pool, consider
using a cartridge lter to jumpstart your pool’s
water eciency. If you are looking to upgrade
to a dierent lter type, it is important to know
whether changing lter systems would require
extensive plumbing alterations to operate
eciently.
The best way to reduce water use is to
minimize the frequency and length of
backwashes or cleanings. Using skimmers and
vacuums to manually remove leaves and debris
can reduce the load on lters and increase
the time before a backwash is necessary.
Installing a pressure gauge on the lter can
help determine when it is time to backwash.
When the water pressure increases by 10
pounds per square inch (psi), a backwash is
usually necessary. You can also consider using
backwash water on your lawn or garden. Just
be sure the backwash water is not freshly
chlorinated, so it is safe for your plants.
Other Ways to Maintain Water Quality
Other ways to maintain pool water quality
include use of ozone, ultraviolet light,
copper-silver ionizers, reverse osmosis, and
nanoltration. Ozone is a disinfectant that can
be used in place of chlorine, and ultraviolet
light is a system that sanitizes pool water.
Copper-silver ionizers are used in conjunction
with low levels of sanitizers (e.g. chlorine,
bromine) and release small amounts of copper
and silver ions into a pool, which kills bacteria
and prevents algae growth. All three methods
can be used to reduce the need for chlorine,
which in turn reduces TDS.
Periodic reverse osmosis (RO) treatment or
nanoltration are alternative methods to
maintain water quality. These processes send
contaminated water through a membrane to
remove particles and generate a wastewater
stream of concentrated contaminants. RO and
nanoltration can be used to reduce TDS levels
in a pool, reduce the use of chemicals such as
chlorine, and can increase the time before any
pool water needs to be dumped. However, RO
treatment systems can be costly and waste a
lot of water depending on their eciency, so
carefully compare water consumption from
a RO system to other methods of treatment.
While permanent RO systems are generally
impractical to use for regular pool water
treatment, some companies oer mobile RO
treatment, where an industrial-sized RO system
can be brought to a property to clean pool
water. Some of these larger RO systems can
recover up to 85 percent of the pool water.
This process is an alternative to dumping and
relling pools.
When working with professionals in design
or pool maintenance, look for companies
with professional certications, like those
certications oered by the Pool & Hot Tub
Alliance.
Leaks
One important way to reduce water loss is
to learn to recognize potential leaks. Annual
water loss from pool leaks is dicult to
quantify, as leaks can often go unnoticed for
extended periods of time. However, small
leaks can quickly turn into big leaks if they go
unattended.
8
Leaks can be found in the pool liner, the pump
seal, pool piping, the pool-to-pipe connection,
pool edges, and in pipe joints. If your pool is
losing more than 2 inches of water per week, or
3 inches in hot, dry areas with high evaporation
rates, then it is likely you have a leak. Wet spots
around the pool, or air bubbles in the water
return pipeline or in the pump strainer can also
be signs of leakage. Installing a water meter can
help you actively monitor water consumption
and identify potential leaks.
You can also add water manually, rather than
automatically, to be aware of your pool’s weekly
water loss. If you have an automatic rell for
your pool, then once every three months, the
automatic ll should be shut o for 24 hours to
test for leaks.
Automatic ll valves can sometimes
malfunction and send water to a pool’s
overow drain. Periodically conrm your ll
valve is shutting o properly by plugging the
overow drain and monitoring if the pool level
is rising. If it is, your ll valve may be stuck in
the open position and should be repaired or
replaced.
In cooler climates, another step to prevent
leaks from forming is to make sure your pool is
properly prepared for the winter. Winterize your
pool by cleaning the pool water and all parts
of the pool, balancing out pool chemicals, and
adding winterization chemicals such as shock
and algaecide, which kills bacteria and algae.
Balancing chemicals is important, as a chemical
imbalance could corrode the pool and lead to
structural damage. It is also important to drain
water from equipment such as lters, pumps,
heaters, and piping, as freezing water can cause
cracks, which can later cause leaks.
Pool Usage
Water can also be lost to splashing and “drag
out,” which is the water that is removed as
a person exits a pool. Like leaks, the total
water loss from splashing and drag out is
hard to quantify, but mitigation techniques
can be implemented during pool design and
construction. Many pools are built such that
the pool edges are cantilevered and divert
water back into the pool. An example of a
cantilevered edge is shown in Figure 5 on
page 9.
Some pools also have a gutter or grate system
around the pool edges to drain water back
Do-It-Yourself Leak Test
It’s important to periodically test for
leaks in the pool by performing an
evaporation bucket test.
1. On a day without rain or heavy
winds, shut down all pool systems
(ltration systems, pool cleaners,
automatic lls, etc.), and close the
pool for 24 hours.
2. Fill a 2.5- to 5-gallon bucket to
about 1 inch from the top and set
the bucket in the pool (on a bench or
step) such that at least two-thirds of
the bucket is submerged in the pool,
and the bucket water level is a little
higher than the pool level.
3. Mark the initial water level within
the bucket with a marker, piece of
tape, or by using a ruler to record the
distance from the top of the bucket.
Mark/measure the initial height of the
still pool water the same way.
4. Leave the bucket for 24 hours, then
re-record the pool and bucket water
levels. If pool water loss is greater than
bucket water loss, the pool may have
a leak.
For more details, refer to the ANSI/
APSP/ICC-13 Standard for Water
Conservation Eciency in Residential
and Public Pools, Spas, Portable Spas,
and Swim Spas.
9
into the pool. Implementing these common
features during the design of your pool will
work to reduce water loss.
You can also reduce water loss from human
activity by preventing overlling and
maintaining water levels at an appropriate
height. Maintain 4 inches of freeboard, or the
distance from the level of the pool water to the
top of the overow or pool deck, to prevent
water overowing when there is activity in
the pool. Also consider plugging the overow
drain(s) when the pool is being used.
More Ways to Improve Water
Efficiency
While draining your pool should be relatively
infrequent, it is sometimes unavoidable to
make repairs or improve overall water quality.
The frequency at which water needs to be
removed can vary depending on local water
quality and conditions, but a well-maintained
pool should only need to be drained every
3 to 7 years to keep TDS levels down. If this
becomes necessary, consider opportunities
for water reuse. Before draining, let the water
sit in your pool for 48 to 72 hours without
adding chemicals; at that point, pool water is
often safe enough for garden or landscape use.
However, be sure to check for local regulations
on pool water discharge before draining your
pool water into sanitary or storm sewers or
onto your property.
Figure 5: Cantilevered Pool Edge
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PHONE (866) WTR-SENS (987-7367) WEBSITE www.epa.gov/watersense EMAIL [email protected]
EPA-832-F-22-015
SEPTEMBER 2022
References and Additional Resources
The following are resources that were used in the development of this guide:
1st Direct Pool. 11 January 2021. “How Often Should You Replace Your Swimming Pool Filter?”
www.1stdirectpools.com/blog/post/how-often-should-you-replace-swimming-pool-lter.
Association of Pool & Spa Professionals (APSP). 6 January 2017. ANSI/APSP/ICC-13 2017 American
National Standard for Water Conservation Eciency in Residential and Public Pools, Spas, Portable
Spas, and Swim Spas. American National Standards Institute. https://webstore.ansi.org/Standards/
APSP/ANSIAPSPICC132017.
APSP. 2014. “Copper-Silver Ionizers.” www.phta.org/pub/?id=082CD55C-1866-DAAC-99FB-
D9CCF4026297.
Aquanomics Pools. 23 August 2017. “Pros and Cons of Dierent Pool Filters.”
www.aquanomicspools.com/pros-and-cons-of-dierent-pool-lters/.
ASTM International (ASTM). February 2018. ASTM F1346 - 91(2018), Standard Performance
Specication for Safety Covers and Labeling Requirements for All Covers for Swimming Pools, Spas and
Hot Tubs. www.astm.org/f1346-91r18.html.
DeOreo W., Mayer P., Kiefer J., Dziegielewski B. 2016. Residential End Uses of Water (REUWS) Study
Update. Water Research Foundation (WRF).
DOE Energy Saver. “Swimming Pool Heating.” www.energy.gov/energysaver/swimming-pool-
heating.
ENERGY STAR. “Pool Pumps.” www.energystar.gov/products/pool_pumps.
Giovanisci, Matt. 4 May 2021. “How to Select the Best Pool Filter.” Swim University,®
www.swimuniversity.com/pool-lter/.
Koeller, John, and H.W. (Bill) Homan & Associates LLC. September 2010. “Evaluation of Potential
Best Management Practices—Pools, Spas, and Fountains.” CalWEP, The California Urban Water
Conservation Council, calwep.org/wp-content/uploads/2021/03/Pools-Spas-and-Fountains-
PBMP-2010.pdf.
Let’s Pool Together. “Pool, Hot Tub & Spa Water Conservation Tips.” Accessed 1 March 2022.
www.letspooltogether.com/pool-spa-tips/.
Minos, Scott. 5 July 2021. “Stay above Water with an Ecient Swimming Pool.” U.S. Department of
Energy (DOE), www.energy.gov/energysaver/articles/stay-above-water-ecient-swimming-pool.
Muleta, Misgana. January 2016. “Cal Poly Study: Eectiveness of Pool Covers to Reduce
Evaporation from Swimming Pools.” National Plasterers Council (NPC), www.npconline.org/page/
cal-poly-study.
Pool & Hot Tub Alliance. Certication. www.phta.org/certication/.
Water – Use It Wisely. “Saving Water Outdoors.” https://wateruseitwisely.com/saving-water-
outdoors/swimming-pools/.
WaterSense. WaterSense at Work: Best Management Practices for Commercial and Institutional
Facilities. www.epa.gov/watersense/best-management-practices.
