A pool losing water raises the same question for every homeowner: is this evaporation or a leak? The answer matters because the response is different. Evaporation is normal physics; a leak is a repair problem that can damage the pool shell, the deck, and the landscaping if ignored. Diagnosing which you have is a 24-hour investigation with free tools.
How much water Florida pools actually lose to evaporation
- Summer peak: 1/4 to 3/4 inch per day.
- Winter: 1/8 to 1/4 inch per day.
- Windy days or low humidity: 2× normal rate.
- Covered pool: 50–70% less.
For a typical residential pool, that's 50–150 gallons per day in summer. This is normal.
The bucket test (24 hours, free)
- Set a 5-gallon bucket on the first or second pool step.
- Fill the bucket with pool water to match the pool's water level exactly.
- Mark both levels (pool and bucket) with tape.
- Leave the pool running normally. Don't swim.
- After 24 hours, compare the drops.
Both drop by the same amount → evaporation only, no leak. Pool drops more than the bucket → you have a leak.
Running the test twice to narrow the leak
If the first bucket test shows a leak, run it a second time with the pump off. Comparing the two results narrows the leak source:
- Leak with pump on, not with pump off— pressure-side leak. Return plumbing, heater, filter, or any line under pump pressure.
- Leak with pump off, not with pump on— suction-side or shell leak. Lines that only drain by gravity when the pump stops.
- Leak both ways— shell leak (plaster crack, failed tile grout, light niche) or a fitting leak above the water line.
Loss rate tells you urgency
| Daily loss (after evaporation) | What it means |
|---|---|
| Under 1/8 inch | Small seepage. May be testing-error noise. Monitor weekly. |
| 1/4 to 1/2 inch | Real leak, moderate. Investigate soon but not emergency. |
| 1/2 to 1 inch | Significant leak. Find it within a few days to prevent secondary damage. |
| Over 1 inch | Major leak. Immediate attention. Risk of deck undermining or shell damage. |
Signs that suggest where to look
- Wet or soft spots on the deck— underground plumbing leak nearby.
- Rising groundwater indicators(muddy landscaping, settling pavers) — underground leak.
- Visible cracks or separation around tile, coping, or skimmer throat — shell leak.
- Chronic wet area near equipment pad— above-ground equipment or plumbing leak.
- Bubbles from returns during normal operation— suction-side air intrusion indicating a leak.
The professional leak-detection process
If the bucket test confirms a leak and you can't locate it visually, a leak detection specialist uses:
- Dye tests at the pool shell for cracks and fittings.
- Pressure testing of plumbing lines.
- Acoustic sensors to locate underground leaks.
- Thermal imaging for underground water paths.
Typical cost: $300–$600 for location. Actual repair is separate and depends on where the leak is.
What NOT to do
- Don't drain the pool to “see” the leak. Florida's water table can float an empty pool.
- Don't add leak-stop chemicals without understanding where the leak is. These can fix small seepage but also permanently clog filters if the leak is elsewhere.
- Don't ignore a confirmed leak hoping it'll self-seal. Water loss undermines decks, stains tile, and can destabilize the shell over months.
The bucket test is the most valuable free diagnostic in pool service. Run it anytime a customer reports water loss. In 80% of cases, the answer is evaporation and the call ends in relief. In the other 20%, you've started the leak investigation on the right foot.