- Fill a 5-gallon bucket with pool water to about two-thirds from the top.Bring the pool water to normal level and start the pool filter pump.
- Place the bucket on the first or second step of the pool. Ensure the bucket is immersed in the pool at least five inches.
- Mark the water level inside the bucket.
- Shut off the pump and mark pool water level on the outside of the bucket.
- Resume normal pool pump operation (or run the pump for at least enough time for all of the water in the pool to have passed through the filter once).
- After 24 hours, compare the two water levels. If the pool water (outside mark) goes down more than the bucket’s water level, there is probably a leak. If levels are the same, only evaporation has occurred.
- In case of rain, repeat the bucket test. Expect water loss from normal evaporation. Test is invalid after 24 hours.
A quarter inch of water loss per day is most likely evaporation. The evaporation rate in your area will depend on humidity, sunlight intensity, barometric pressure, wind and the level of activity in the pool or spa.