Pools & water systems / Level check
Measure pool water change
Enter the surface area and level drop to see the volume change between readings.
Level measurement
Water volume change
Enter surface area square metres.
How it works
Put in your numbers
Use your own rates, times and measurements.
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What it covers: Convert a measured level drop into volume, and compare it with a bucket test.
Free to use. No sign-in needed.
How to measure pool water loss
If a pool level keeps dropping, measuring it properly helps you decide whether it needs investigating. This calculator turns a measured level drop into a volume of water and lets you compare it with a bucket test. It does not tell you the cause.
- Work out the water surface area in square metres or square feet. For a simple rectangle, multiply length by width.
- Mark the water level, for example with tape on the tile or skimmer opening, and note the time.
- Measure again later and record how far the level dropped and the hours between the two readings.
- Enter the surface area, level drop and hours. The calculator shows the volume lost and the same rate over 24 hours.
- For a bucket test, set a bucket of pool water on a pool step, mark the level inside the bucket and on the pool, and measure both drops over the same period. Enter the bucket drop and the calculator shows how much more the pool lost.
Tips and common mistakes
- Keep conditions the same between readings. Swimming, splash-out, backwashing or topping up will throw off the result.
- Measure the drop carefully in millimetres or fractions of an inch. A small error makes a big difference to the volume on a large pool.
- If the pool drops noticeably more than the bucket, something other than evaporation is likely taking water and it is worth investigating further.
- Try one test with the pump running and one with it off. A difference between them can help narrow down where water is going.
Questions
How do I know if my pool is leaking?
Do a bucket test. Set a bucket of pool water on a step so it sits in the same conditions, mark the water in the bucket and the pool, and compare after a day. If the pool level drops noticeably more than the bucket, a leak is possible and worth checking.
How much water does a pool lose to evaporation?
It varies a lot with sun, wind, humidity, water temperature and whether a cover is used. A bucket test shows evaporation in the same conditions as your pool. Compare the bucket drop with the pool drop rather than relying on a general figure.
How do I do a bucket test on a pool?
Fill a bucket with pool water and set it on a pool step so the water inside is about level with the pool. Mark the level inside the bucket and on the pool wall, then avoid swimming or topping up. After about 24 hours, compare how far each level has dropped.
How do I work out how much water my pool has lost?
Multiply the water surface area by the level drop, using the same units. As an illustration only, a 32 m² surface that drops 10 mm (0.01 m) has lost 0.32 cubic metres, which is 320 litres. The calculator does this sum for you.
Is it normal for a pool to lose water?
Some loss from evaporation, splash-out and backwashing is normal. What matters is whether the loss is more than those causes explain. Regular measurements and a bucket test help you tell the difference.
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