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.
Frequently asked questions
Set a 5-gallon bucket on the first or second pool step and fill it with pool water so the bucket's water level matches the pool's exactly. Mark both levels with tape, leave the pump running normally, and don't swim. After 24 hours, compare the two drops. If both dropped the same amount, it's evaporation only. If the pool dropped more than the bucket, you have a leak.
If the first test confirms a leak, run it again with the pump off and compare. Losing water only with the pump on points to a pressure-side leak in the return plumbing, heater, or filter. Losing water only with the pump off points to a suction-side or shell leak that drains by gravity. Losing it both ways points to a shell leak like a plaster crack or failed tile grout, or a fitting leak above the water line.
Loss rate after evaporation tells you the urgency. Under 1/8 inch a day is small seepage or testing noise you can monitor weekly. A quarter to a half inch is a real, moderate leak to investigate soon. A half to one inch is significant and should be found within a few days. Over one inch a day is a major leak that needs immediate attention before it undermines the deck or shell.
Don't drain it. Florida's high water table can float an empty pool right out of the ground. Also skip pouring in leak-stop chemicals blindly. They can seal small seepage, but if the leak is somewhere else they'll permanently clog your filter. And don't ignore a confirmed leak hoping it self-seals, because ongoing water loss undermines decks, stains tile, and can destabilize the shell over months.
When the bucket test confirms a leak and you can't spot it visually, a leak-detection specialist uses dye tests at the shell for cracks and fittings, pressure tests the plumbing lines, and runs acoustic sensors and thermal imaging to trace underground water paths. Location typically runs $300 to $600. The actual repair is a separate cost that depends on where the leak turns out to be.
Wet or soft spots on the deck suggest an underground plumbing leak nearby. Muddy landscaping or settling pavers point to an underground leak. Cracks or separation around tile, coping, or the skimmer throat point to a shell leak. A chronic wet area at the equipment pad means an above-ground plumbing leak. Bubbles from the returns during normal operation indicate suction-side air intrusion.
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