Is My Pool Leaking? Use the Bucket Test to Find Out

If your pool keeps dropping and you are topping it up more than usual, the question is always the same: is it a leak, or just evaporation? The bucket test answers it. Do the two-minute test, enter your measurements below, and get a clear answer in seconds.

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Leak or evaporation? Check your pool

Enter your two measurements from the bucket test.

A full 24 hours is ideal. Longer is even more accurate.

hours

Measure the fall at the tile line or skimmer, in millimetres.

mm

Your control. Same spot, same time. This is pure evaporation.

mm

Roughly is fine. Used only to estimate litres and cost.

m
m

What the bucket test tells you

Your pool and a bucket of pool water sitting on the steps both lose water to evaporation at the same rate. That is the whole idea. If, after 24 hours, your pool has dropped by more than the bucket, that extra water is not evaporating. It is escaping, through the shell, a fitting, the liner or the underground pipework.

How to do the bucket test

  • Stand a bucket on the first or second step so it sits in the water.
  • Fill the bucket with pool water to match the pool's level exactly.
  • Mark the water level inside the bucket and on the pool wall.
  • Switch off the pump and any auto-fill, and leave it 24 hours without swimming.
  • Measure how far each has dropped, then enter both figures in the calculator.

How much water loss is normal?

Some loss is completely normal. A pool typically loses around 2 to 5mm a day to evaporation, and more in hot, dry or windy weather, when it can reach 5 to 10mm or beyond. Wind and sun matter more than most people expect. That is exactly why the bucket is there: it loses water to the same weather, so whatever the pool loses on top of the bucket is the part worth worrying about.

Signs it is a leak, not evaporation

  • You are topping up far more often than you used to.
  • The pool keeps dropping even in cool, still weather.
  • Damp patches, soft ground or unusually lush grass near the pool or plant room.
  • Cracks in the shell or around fittings, lights and the skimmer.
  • The water settles at one particular level and stops.

Found a leak? Here is what happens next

The important thing is to trace it properly before it does damage. A leak can wash out the ground around the shell, undermine the structure and quietly run up your water bill. We find the source with the pool still full, using pressure testing, dye testing, acoustic and trace-gas detection and underwater inspection, so you avoid the cost and risk of draining. You get a clear report of exactly what is wrong and where, so the right thing gets fixed once.

Not sure, or want it checked properly?

We are independent pool surveyors and leak detection specialists. Talk to us and we will find it, fast.

📞 01234 783569 ✉️ info@swimmingpoolsurveys.co.uk 🌐 swimmingpoolsurveys.co.uk

Frequently asked questions

How much water should a swimming pool lose per day?
A pool usually loses about 2 to 5mm a day to evaporation, and more in hot, dry or windy weather. If yours drops noticeably more than a control bucket over the same 24 hours, that extra loss points to a leak rather than evaporation.
How do I know if my pool is leaking or just evaporating?
Do the bucket test. Float a bucket of pool water on the steps, mark both the bucket and pool levels, wait 24 hours, then compare. The bucket loses water only to evaporation, so if the pool has dropped more than the bucket, the difference is a likely leak. The calculator on this page does the maths for you.
Can you find a pool leak without draining the pool?
Yes. We pinpoint leaks with the pool still full using pressure testing, dye testing, acoustic and trace-gas detection and underwater inspection. Draining a pool to look for a leak is slow, costly and can even risk the structure, so we avoid it.
Is it normal for a pool to lose water in summer?
Yes, some loss is normal and it increases in summer heat, sun and wind. The bucket test is reliable in any season because the bucket evaporates at the same rate as the pool, so it separates normal summer evaporation from a genuine leak.
What happens if I ignore a pool leak?
Beyond the wasted water and higher bills, a leak can wash out the ground around the shell, undermine the structure and damage surrounding areas. The sooner it is traced, the cheaper and simpler it is to put right, which is why a quick survey is worth it.