Perth water guide
Why your pool bill spiked, and how to tell evaporation from a leak.
A high Water Corporation bill usually comes down to one of two things: the weather, or a leak. Here is how to tell which, what the rules actually allow, and a five-minute check you can do today.
Two reasons a pool drinks more than it should
A pool loses water two ways that matter for your bill. Evaporation, which the weather drives and which the rules expect you to replace. And a leak, which the weather has nothing to do with — the water is escaping the shell or the plumbing and you are paying to refill it.
Telling the two apart is the whole game. Top up to cover evaporation and you are within the rules and spending what you should. Top up to cover a leak and you are paying for water you never see — and, technically, topping above what the rules allow.
How much loss is just evaporation
Above 38°C in a Perth summer, evaporation alone runs about 5–8mm a day. Through a mild, still week it is a fraction of that. So the same one-centimetre drop means very different things in February and in July.
The rule of thumb: a pool dropping about a centimetre a day when the weather is mild is almost certainly losing water somewhere it shouldn’t. In a heatwave, that same drop can be honest evaporation. The weather is the context you have to measure against before you call anything a leak.
The bucket test — a five-minute check you can do today
Before you call anyone, this is the simplest way to separate evaporation from a leak. It costs nothing and takes a day.
Float a bucket of pool water
Fill a bucket about three-quarters with pool water and stand it on a step so it sits partly submerged — weight it if it wants to float. Sharing the pool's water means both lose to the same sun and wind.
Mark both levels
Mark the water level inside the bucket and the pool's level on the skimmer or tile. A strip of tape on each works well.
Leave it 24 hours
Keep the pump running as normal, no swimming, and pick a window with no rain. The two are now losing water under the same conditions.
Compare the two drops
If the pool fell about the same as the bucket, that is evaporation. If the pool fell noticeably more, the extra water is going somewhere it shouldn't — a leak.
The bucket test tells you whether you have a leak, not where it is. Finding where the water goes is the diagnostic — see how a diagnostic works and the instruments we use.
If the bill came with a Water Corporation alert
WA permanent water rules allow pool top-up only to replace evaporation. A pool consistently topping above evaporation rates is operating outside the rules — and Water Corporation high-bill alerts often follow. Our written report is formatted to support a Water Corp dispute.
The same report supports an insurance claim where the leak has caused damage. A clear, evidenced finding — what failed, where, and the repair quote — is what turns “we think it’s a leak” into something you can act on with the utility or your insurer.
What we do once the bucket test points to a leak
We measure the pool’s real loss against the day’s conditions, isolate the plumbing from the shell with a pressure test, trace any buried line with an acoustic ground microphone, and on Tier B dive the pool to inspect the shell and fittings at depth. Within 24 hours you get a written report: where the water is going, the evidence, photos, and a repair quote where the leak is repairable.
We work Perth metro, Two Rocks to Mandurah. If you’re outside, send us a postcode — we’ll let you know honestly whether the trip makes sense for both of us.
Bucket test says it’s a leak?
Book a fixed-price diagnostic this week, or look at the two tiers first.