The most effective way to save water in a swimming pool is to cover it whenever no one is swimming: the U.S. Department of Energy says a pool cover can cut the make-up water a pool needs by 30% to 50% (DOE Energy Saver, 2026). After a cover, the biggest savings come from finding leaks early, backwashing only when the filter needs it and keeping the water balanced so the pool never has to be drained.
Here are nine ways to keep more water in your pool, starting with the ones that save the most.
Where does pool water go?
A pool loses water in five main ways: evaporation, leaks, backwashing the filter, splash-out and draining. Evaporation is usually the largest. The City of Mesa, Arizona says a typical swimming pool can lose as much as 25,000 gallons of water to evaporation in a year, and its chart for a 400-square-foot pool in Phoenix-area weather shows about 79 inches (19,664 gallons) lost over 12 months, with the most in June (City of Mesa, 2026). Pools in cooler, more humid places lose less, but the same causes apply everywhere.
According to the U.S. Department of Energy, the higher the pool temperature and wind speed and the lower the humidity, the faster a pool evaporates.
1. Does a pool cover really save water?
Yes. A pool cover is the single biggest water saver for most pools because it blocks evaporation at the surface. The U.S. Department of Energy says a cover can reduce the make-up water a pool needs by 30% to 50%, cut the pool’s chemical use by 35% to 60%, and save 50% to 70% on pool heating costs (DOE Energy Saver, 2026). The DOE also notes that evaporation is by far the largest source of energy loss in a pool, so a cover saves water and heat at the same time.
Indoor pools benefit too. The DOE says covers on indoor pools reduce evaporation and the need to ventilate the room, and exhaust fans can be shut off while the pool is covered.
2. How do I know if my pool is leaking?
Use a bucket test to tell a leak from normal evaporation. The City of Mesa describes it this way (City of Mesa, 2026):
- Turn off the pool’s automatic fill valve, if it has one.
- Set a weighted bucket on the top step, fill it to the same level as the pool water, and mark both water lines.
- After two or three days, compare the two drops. If the pool dropped more than the bucket, the pool is probably leaking.
- Repeat the test once with the pump running and once with it off. If the pool loses more water with the pump on, the plumbing is the likely cause.
Leaks are common and easy to miss. The City of Chandler, Arizona estimates that 30% of all pools have a leak, and says a fill valve stuck open can waste up to 30,000 gallons in a month (City of Chandler, 2026).
Small leaks add up. A leak that drops the water one inch a day in a 15-by-30-foot pool loses about 280 gallons a day (450 square feet times 1/12 foot is 37.5 cubic feet, and a cubic foot holds about 7.48 gallons). Over a year that is about 102,000 gallons. For step-by-step help finding the source, see Swimming Pool Leak Detection 101.
3. Does lowering the pool temperature reduce evaporation?
Yes. Warmer water evaporates faster, so a lower water temperature means less water lost and less energy spent heating it (DOE Energy Saver, 2026). If you heat your pool or spa, set it a few degrees lower when you can and cover it when it is not in use. For help choosing a setting, see What Is the Best Pool Temperature?
4. Do fountains and waterfalls waste pool water?
They can. Fountains, waterfalls and slides throw water into the air, which speeds up evaporation, and some of that water lands outside the pool. The Northern Territory Government in Australia advises running fountains and waterfalls only when you are entertaining because they increase evaporation (Northern Territory Government, 2026), and the City of Mesa recommends turning water features off when they are not in use (City of Mesa, 2026).
5. How often should I backwash my pool filter?
Backwash a sand filter (or any filter that backwashes) only when it needs it, and stop as soon as the water runs clear. The City of Chandler says the average backwash uses between 250 and 1,000 gallons of water (City of Chandler, 2026), so backwashing on a fixed schedule instead of when the filter needs it wastes a lot of water. Watch the filter’s pressure gauge and follow the manufacturer’s guidance on when to clean it.
Two other habits help. A skimmer sock (a fine mesh liner for the skimmer basket) catches debris before it reaches the filter, which means fewer backwashes (City of Chandler, 2026). Cartridge filters do not need backwashing at all: they can be removed and cleaned by hand by rinsing and soaking them (Northern Territory Government, 2026).
6. How does water chemistry affect how much water a pool uses?
Balanced water saves water because it avoids draining and refilling. The City of Mesa recommends keeping the chemical balance in range to avoid frequent draining, asking a pool professional before draining, and looking at pool water recycling services as an alternative to a full drain (City of Mesa, 2026). Run the pump long enough each day to keep the water circulating and filtered, and test the water regularly so small problems do not turn into a drain.
A steady, low chlorine level is easier to hold with a supplemental system. In a home pool with Clear Comfort’s hydroxyl-based AOP, a typical free chlorine range is 0.5 to 1.5 ppm; a low chlorine residual is still needed. For target levels and dosing, see How Much Chlorine to Add to a Pool.
7. How full should a swimming pool be?
Keep the water about halfway up the skimmer opening. The City of Chandler says this level helps minimize splash-out (City of Chandler, 2026), and the City of Mesa notes that overfilling leads to water lost from splashing (City of Mesa, 2026). When you fill the pool, stay nearby or set a timer so it does not run over, and check that an automatic fill valve shuts off the way it should.
8. How do I reduce splash-out?
Splash-out is water carried out of the pool by swimmers, games and equipment. Ask swimmers to skip cannonballs when water is tight, keep the water at the right level, and turn off the spray or tail on an automatic pool cleaner if it throws water out of the pool. The Northern Territory Government also suggests lowering the water level a little during heavy use to reduce splashing losses (Northern Territory Government, 2026).
9. Can I reuse backwash or drained pool water?
Sometimes. The cities of Mesa and Chandler suggest reusing drained or backwash water on salt-tolerant landscape plants, after letting it sit for up to 72 hours with no new chemicals added (City of Mesa, 2026; City of Chandler, 2026). Check your local rules first: many cities limit where pool water can be discharged.
Saving water is one part of running a lower-impact pool. For energy and chemical steps too, see How to Make Your Pool More Eco-Friendly.
Frequently asked questions
How much water does a swimming pool lose to evaporation?
It depends on climate, but it can be a lot. The City of Mesa, Arizona says a typical pool can lose as much as 25,000 gallons a year to evaporation, and its chart for a 400-square-foot pool shows about 79 inches lost over 12 months in Phoenix-area weather. Pools in cooler, more humid climates lose less.
How much water does a pool cover save?
The U.S. Department of Energy says a pool cover can reduce the make-up water a pool needs by 30% to 50%. The same cover can also cut chemical use by 35% to 60% and pool heating costs by 50% to 70%.
How can I tell if my pool is leaking or just evaporating?
Do a bucket test. Turn off the auto-fill, set a weighted bucket of pool water on the top step, mark both water lines and compare them after two or three days. If the pool drops more than the bucket, the pool is probably leaking.
How much water does backwashing a pool filter use?
The City of Chandler, Arizona says an average backwash uses 250 to 1,000 gallons of water. Backwash only when the filter needs it and stop once the water runs clear.
Should I drain my pool every year?
Most pools do not need a yearly drain. Keeping the water balanced helps you avoid draining, and pool water recycling services can be an alternative to a full drain. Ask a pool professional before draining.
Want a low-chlorine home pool that is easier to keep balanced? See Clear Comfort’s residential AOP systems.
