A pool that’s dropping a centimetre or two a week sends a lot of owners into a panic. Often it’s just evaporation. Sometimes it isn’t. Before you call anyone, there’s a five-minute test that tells you which.
First, know what’s normal
All pools lose water to evaporation, and more than people expect — warm, breezy or uncovered pools especially. Losing up to around 3–5mm a day in summer can be perfectly normal. The trick is separating that everyday loss from a genuine leak, and the bucket test does exactly that.
The bucket test
- Fill a bucket with pool water and stand it on a step so it’s partly submerged.
- Mark the water level inside the bucket and the pool level outside it, at the same time.
- Leave both for 24–48 hours (don’t swim, and keep the pump running as normal).
- Compare the two drops.
Reading the result
If the pool and the bucket dropped by the same amount, it’s evaporation — both lost water to the air equally. If the pool dropped noticeably more than the bucket, water is leaving the pool by another route. That’s a leak.
Signs it’s a leak, not the weather
- Loss that doesn’t track the weather — dropping fast on cool, still days too.
- Soggy or sunken ground around the pool, or unusually lush patches.
- Air in the system — bubbles at the returns, or the pump losing prime.
- Needing to top up far more often than last season for no clear reason.
The bucket test won’t tell you where the leak is — only that you have one. That part’s our job.
Where pool leaks usually are
Common culprits are the structure itself (cracks in the shell or liner), the fittings (lights, returns, skimmers), and the buried pipework to and from the plant room — the last of which is invisible and the reason DIY rarely settles it. We use pressure testing on the lines and tracer methods on the structure to find the exact point without draining and digging the whole thing up.
So: do the bucket test first. If it points to a leak, that’s the moment to call — and you’ll already know more than most people do when they pick up the phone.