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Every summer, pool owners ask the same question. Is the missing water just evaporation, or is there a leak? Getting it wrong is costly either way. Mistake a leak for evaporation and water keeps escaping under the pool, weakening soil and waterproofing. Mistake evaporation for a leak and you may pay for tests and breaking you did not need. This guide explains how evaporation works, what increases it, and how to run and read the bucket test with confidence.
How pool water evaporates
Evaporation is water leaving the surface into the air. The drier, hotter and windier the air, the more water it pulls from the pool. A pool in a dry inland city like Riyadh loses more to evaporation than the same pool in a humid coastal city. Evaporation happens only at the surface, so a wide shallow pool loses more than a smaller, deeper one holding similar volume.
What raises or lowers evaporation
| Factor | Raises it | Lowers it |
|---|---|---|
| Sun | Direct exposure all day | Partial shade or pergola |
| Air | Hot and dry | Cooler and more humid |
| Wind | Constant wind over the surface | Walls or buildings blocking it |
| Water temperature | Warm or heated water | Water cooler than the air |
| Water movement | Waterfalls, fountains, jets | Calm surface |
| Cover | Uncovered day and night | Cover used when not swimming |
That is why you cannot compare your pool directly with a neighbour's. The right comparison is with water sitting in exactly the same conditions, which is the whole idea of the bucket test.
The bucket test, step by step
- Choose a sturdy plastic bucket with fairly straight sides and place it on the first or second pool step, partly submerged.
- Weigh it down with a clean stone so it does not move or float.
- Fill it with pool water to roughly match the pool level outside.
- Mark both levels, inside the bucket and on the pool wall or outside of the bucket.
- Turn off auto-fill and do not swim during the test.
- Run the pump as usual for the first test, then repeat on another day with the pump off.
- Compare after a full day or two how far each level has dropped.
Reading the result
- Similar drop in bucket and pool means normal evaporation.
- The pool dropped clearly more means extra loss beyond evaporation, most likely a leak.
- Bigger gap with the pump on suggests the pressure lines after the pump.
- Bigger gap with the pump off suggests the suction line or the shell.
- Odd results, such as the bucket dropping more, usually mean it moved; run it again.
The bucket test tells you whether there is a leak, not where. Locating it takes further steps, covered in our guide to professional leak detection steps.
Signs that confirm a leak even without a test
- Damp or soft ground around the pool or garden without irrigation.
- Cracks in surrounding paving or slight sinking of paths.
- Damp or efflorescence on a basement or adjacent room wall.
- Constant air bubbles from return jets.
- An unexplained jump in the water bill from constant topping up.
- Higher chemical use because fresh water keeps coming in.
When to worry and what to do
If the test shows a clear gap or any of these signs appear, do not wait. A small leak rarely stays small, because escaping water carries soil particles and widens its path, potentially reaching foundations or causing paths to settle. At the same time, do not start breaking anything before the source is pinpointed.
YAM Pools begins with an on-site inspection using pressure tests and targeted checks, then provides a report and written quotation covering only the repair needed, with a written warranty on workmanship and waterproofing. We serve Riyadh and all cities across Saudi Arabia.
- Heat, dry air, wind and moving water increase evaporation.
- The bucket test is the simplest reliable way to tell the difference.
- Test with the pump on and off.
- Damp around the pool is never caused by evaporation.
- Locate the source before any breaking.
Frequently asked questions
Can all this loss really be evaporation?
On hot, dry, windy days evaporation can be higher than you expect, especially with a waterfall or fountain. The bucket test settles whether all of it is evaporation.
Does a pool cover reduce evaporation?
Yes. A cover is one of the most effective ways to cut evaporation when the pool is not in use, and it also keeps dust out and preserves chemicals.
How many times should I repeat the bucket test?
At least twice, once with the pump on and once off, on days with ordinary weather.
Does the bucket test show where the leak is?
No. It only confirms abnormal loss. Locating the leak needs pressure tests and a specialist inspection.
