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Turn a green pool clear again: test, brush, shock to the right level for your stabilizer, run the filter and vacuum. Doses, timelines and mistakes to avoid.
Is My Pool Leaking? The Bucket Test
How to tell a pool leak from evaporation with the bucket test, how to read the results, where leaks usually hide and when to call a leak detection pro.
Key takeaways
- The bucket test compares your pool’s water loss with evaporation from a bucket sitting in the same conditions.
- If the pool drops noticeably more than the bucket over 24 hours, you probably have a leak.
- Repeat the test with the pump off to narrow down whether the leak is in the plumbing or the pool itself.
On this page
To find out whether your pool is leaking, do the bucket test. Fill a bucket with pool water, set it on a pool step so the water inside matches the pool’s level, mark both levels and check them 24 hours later. Evaporation lowers both by about the same amount. If the pool has dropped noticeably more than the bucket, water is going somewhere else, and you probably have a leak.
Why pools lose water normally
Every pool loses water to evaporation. The U.S. Department of Energy notes that the evaporation rate depends on the pool’s temperature, the air temperature and humidity, and the wind speed at the surface. Hot, dry, windy days can take a surprising amount, and splashing, backwashing and vacuuming to waste take more. That’s why a falling level alone doesn’t prove a leak; the bucket test separates the two.
What you need
- A plastic bucket (a 5-gallon bucket is ideal)
- A waterproof marker or strips of duct tape
- Pool water
- A couple of bricks or stones, if the bucket needs weighting on the step
How to do the bucket test
- Top up the pool to its normal operating level and switch off any automatic filler.
- Place the bucket on a step so its rim sits well above the pool surface. On an above-ground pool, use a ladder step or a sturdy stool in the shallow area.
- Fill the bucket with pool water until the level inside matches the pool level outside.
- Mark both levels: the water line inside the bucket, and the pool level on the outside of the bucket.
- Run the pump as usual and leave everything for 24 hours. Don’t swim, and avoid testing when rain is forecast.
- Compare the drops. Measure how far each level fell from its mark.
Reading the results
| Result after 24 hours | What it suggests |
|---|---|
| Pool and bucket dropped about the same | Evaporation; no leak |
| Pool dropped noticeably more than the bucket | Likely leak |
| Pool dropped more with the pump running | Leak probably on the pressure side: return lines or equipment |
| Pool dropped more with the pump off | Leak possibly on the suction side: skimmer or suction lines |
| Same loss with the pump on or off | Leak probably in the pool itself: shell, liner, light or fittings |
Repeat the test with the pump off
Run a second 24-hour test with the pump off (and the bucket reset). Comparing the two results is the best free clue to where the water is going. Pressure-side leaks push water out while the pump runs; suction-side leaks can pull air in while it runs and leak water when it stops.
Other signs of a leak
- Wet, soggy or sinking ground around the pool or equipment
- Cracks in the deck, shell or tiles
- Air bubbles in the pump basket or returns (a suction-side leak)
- Algae that keeps returning, or chemicals that never stay balanced
- A water bill or top-up routine that has crept up
- Loose tiles or a liner that’s shifted or wrinkled
Finding the leak
- Watch where the level stops. If the water stops dropping at the skimmer mouth, a light or a return, the leak is probably at that height.
- Do a dye test. Turn the pump off and let the water go still. Squirt a little leak-detection dye (or food coloring) next to suspect spots: cracks, the skimmer throat, returns, lights, step corners and liner tears. If the dye is drawn in, you’ve found it.
- Inspect the equipment pad. Look for drips at the pump, filter, heater, valves and unions, and feel for damp pipes.
When to call a professional
If the bucket test confirms a leak but you can’t find it, professional leak detection is worth the cost. Specialists pressure-test the plumbing lines and use listening equipment and dye to pinpoint leaks without digging up the deck. Leaks in underground plumbing, main drains or structural cracks need professional repair.
After the repair
Fresh top-up water dilutes your chemistry. Retest everything, and use our pool chemical dosage calculator to rebalance. Stabilizer is often the reading that falls furthest after a long leak; our cyanuric acid guide explains the right level. If your fill water is hard, keep an eye on calcium hardness too. Adding a quick level check to your pool opening checklist catches winter damage early.
Frequently asked questions
How much water loss is normal for a pool?
It varies with weather: hot, dry and windy days evaporate much more than cool, humid ones. That’s why the bucket test compares against real evaporation on the same day rather than using a fixed number.
Does rain ruin the bucket test?
Yes. Rain adds water to the pool and the bucket in different amounts. Start again after a dry 24 hours.
Can a pool leak through the skimmer?
Yes. The skimmer throat, where it joins the pool wall, is a common leak point, especially in older pools. A dye test around the skimmer with the pump off often finds it.
Sources
Every article is edited by a human and checked against our editorial policy. Spotted a mistake? Tell us.
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