The bucket test: is your pool leaking or just evaporating?
A bucket, a marker and 24 hours tell you whether the pool is leaking. Here is how to run the test and what the result means.
Every pool loses water. In Conejo Valley summer heat with a little wind, a quarter inch a day is normal evaporation, and a heated spa or a Santa Ana week can double that. The bucket test tells you in a day whether what you're seeing is weather or a leak, and it costs nothing.
The test
- Fill the pool to its normal level and turn off the autofill if you have one.
- Set a bucket on the second step and fill it so the water inside matches the pool level outside. Weigh it down with a brick if it floats.
- Mark the water level inside the bucket and on the outside of the bucket with tape or a marker.
- Turn the pump off and wait 24 hours. No swimming.
- Compare the two marks. Evaporation lowers both the same. If the pool dropped more than the bucket did, you have a leak.
- Repeat with the pump running for 24 hours.
Reading the result
If the pool loses more with the pump off than on, the leak is on the suction side or in the shell: a skimmer throat, the light niche, a return fitting or a crack. If it loses more with the pump running, the leak is on the pressure side, in the plumbing between the pump and the returns, which is often underground. The same loss either way points to the shell. Those three answers are what a leak tech wants to know on the phone.
Where leaks usually are
The equipment pad first: a weeping pump seal, a filter drain plug, a heater that drips when it's running. Then the skimmer, where the plastic throat meets the concrete. Then the light niche and the conduit behind it. Returns and spa spillovers after that. Cracks in the shell and underground plumbing are last on the list, which is why most leak repairs never touch the deck.
Other signs
- The autofill runs all the time.
- Air bubbles at the returns, or air under the pump lid, with the water level fine. A suction leak pulls air in when the pump is on and lets water out when it's off.
- Wet or soft ground near the pad or along the deck edge.
- Chemistry that won't hold, because fresh fill water keeps diluting it.
What to do next
Keep the water above the skimmer so the pump doesn't run dry, and keep filling until it's fixed. Leak detection is pressure testing on each line and dye testing around the fittings, and when the leak is at the pad or the skimmer, which it usually is, the repair is often the same visit.