How Much Water Should a Pool Lose to Evaporation in Southern California?
There is no single normal evaporation number for every Southern California pool. Heat, low humidity, wind, water temperature, sun exposure, surface area and waterfalls can all increase loss. Many references describe broad weekly losses that can reach inches under demanding conditions, but a change from your pool’s normal pattern is more useful than a universal cutoff.
CONDITIONS THAT INCREASE EVAPORATION
• Hot, dry air above the water.
• Wind that removes humid air from the pool surface.
• Warm pool water, especially when nights are cool or dry.
• Waterfalls, spillways, deck jets and aeration.
• Large exposed surface area.
• An uncovered pool.
Southern California’s inland heat and Santa Ana winds can create very different losses from a mild, still week. Splash-out and backwashing also lower the water level but are not evaporation.
ESTABLISH YOUR POOL’S NORMAL PATTERN
Mark or photograph the waterline at the same time of day and compare it over several days with similar weather and equipment operation. Note recent swimming, backwashing, autofill operation and water-feature schedules.
A bucket test can help compare water lost from the pool with water lost from a container exposed to the same weather. Follow a reliable procedure and disable the autofill during the observation so added water does not hide the result.
SIGNS THE LOSS MAY BE A LEAK
• The level drops faster than a nearby bucket comparison.
• The autofill runs much more often than usual.
• Water loss continues during mild, calm weather.
• Wet soil, deck cracks, air in the system or unexplained chemical demand appears.
• Loss changes when the pump runs or stops.
REDUCE AVOIDABLE WATER LOSS
A properly fitted cover can greatly reduce evaporation when used safely. Repair splash-out problems, operate water features only when wanted and maintain the water at the appropriate level rather than overfilling.
If the pattern looks abnormal, review pool leak detection — https://www.superiorpoolpro.com/pool-leak-detection and request an evaluation — https://www.superiorpoolpro.com/contact-us. Do not keep refilling indefinitely without investigating; added water also changes chemistry.
FAQ
Is one inch per week always normal? No. It may be plausible in some conditions and abnormal in others. Weather, pool design and the pool’s established baseline matter.
Can an autofill hide a leak? Yes. It can replace lost water automatically while increasing the water bill and diluting pool chemistry.
Source: U.S. EPA WaterSense pool water-efficiency guidance — https://www.epa.gov/watersense/pool-water-efficiency.
