Pool water loss is one of the most common and most frequently misdiagnosed concerns pool owners have. The majority of calls about "leaking pools" turn out to be evaporation — which can be surprisingly significant in Florida's heat and sun. Before calling a leak detection company, the bucket test will tell you definitively whether you have a real leak or normal water loss.
The bucket test — the definitive evaporation vs. leak test
The bucket test establishes your pool's actual evaporation rate and compares it to the pool's water loss, isolating whether there's a leak beyond what evaporation explains.
How to perform it:
- Fill a 5-gallon bucket with pool water to within 1–2 inches of the top.
- Set the bucket on a pool step so it's sitting in the pool water (not on the deck) — this ensures the bucket water and pool water are at the same temperature, giving an apples-to-apples evaporation comparison.
- Mark the water level inside the bucket with a piece of tape or a waterproof marker.
- Mark the pool water level on the bucket's outside, or on the pool skimmer or step.
- Turn off auto-fill if your pool has one, and don't add water during the test.
- Wait 24 hours without swimming (swimming activity displaces water and skews results).
- Compare: measure how much the bucket level dropped vs. how much the pool level dropped.
Interpreting the results:
- If the pool and bucket dropped by the same amount → the loss is evaporation, not a leak. No further action needed on the leak front.
- If the pool dropped significantly more than the bucket → the difference is actual water loss beyond evaporation. You have a leak.
A pool losing 1/4 inch per day beyond evaporation is worth investigating. Losing 1/2 inch or more per day beyond evaporation is significant and should be addressed promptly — both for water cost and to prevent soil erosion or structural damage from persistent underground water loss.
Normal evaporation rates in Florida
Florida's combination of heat, sun, and often dry winter air makes evaporation significant. A typical open residential pool in Tampa Bay can lose 1/4 to 1/2 inch per day to evaporation during summer — occasionally more during periods of low humidity and high heat. A pool cover dramatically reduces evaporation (and chemical loss), but most Florida residential pools don't use covers regularly. If your pool is losing water but the bucket test shows equal loss in both, evaporation is your explanation.
Common leak locations
If the bucket test confirms a leak, the next step is locating it. Some are straightforward to identify; others require professional leak detection equipment.
Skimmer: The skimmer body can crack at the pool wall joint — one of the most common leak sources in Florida pools due to ground movement and thermal cycling. A crack here is often visible on inspection. To test: apply pool putty or plumber's putty over the skimmer throat and repeat the bucket test. If the pool level holds, the skimmer is the source.
Return fittings: The fittings where return lines enter the pool wall can develop leaks at their gaskets or in the surrounding plaster. Inspect for visible cracks or wet spots in the plaster around return openings.
Light fixture: Pool light conduit is a common leak point — water follows the conduit out of the pool. If your leak stops when water drops to the level of the light, the light niche or conduit is the source.
Main drain: Leaks at the main drain fitting or in the suction line below are harder to identify without professional equipment.
Underground plumbing: Leaks in underground supply or return lines are the most serious — they can be difficult to locate and require excavation to repair. Professional leak detection using pressure testing and listening equipment is typically needed to pinpoint these.
The pump-on vs. pump-off test
After confirming a leak with the bucket test, this secondary test helps narrow down whether the leak is in the plumbing (pressurized lines) or in the shell (structure):
- Run the bucket test with the pump running normally for 24 hours, noting the loss rate.
- Then run the bucket test with the pump off (plug the returns and skimmer so the pool is static) for another 24 hours.
- If the pool loses more water with the pump on than off → the leak is in the pressurized plumbing — supply or return lines, equipment connections.
- If the pool loses more water with the pump off → the leak is in the shell — the pool structure itself, fittings, or the light conduit.
- If loss is similar both ways → could be either, or multiple sources.
When to call a professional leak detection company
Once you've confirmed a leak and done the pump-on/pump-off test to narrow the source, professional leak detection is the appropriate next step if you can't visually identify the source. Modern leak detection uses pressure testing of plumbing lines and electronic listening equipment to pinpoint leaks without destructive investigation. The cost is typically $200–$400 for a professional leak detection visit — money well spent to avoid digging in the wrong place.