Most pools lose some water every week, and in a Sydney summer it is usually evaporation, splash-out and backwashing, not a leak. If the level keeps dropping noticeably, even in cool, calm weather, or drops just as fast when the pump is off, you may have a leak. A simple bucket test tells you which one you have before you spend anything.
Normal water loss
Before you suspect a leak, rule out the everyday causes:
- Evaporation: hot sun, dry air and wind pull water off the surface. Western Sydney summers and exposed blocks lose more than a sheltered yard. Heated pools lose more too.
- Splash-out and play: kids, bombing and dogs carry a surprising amount of water over the edge.
- Backwashing and filter cleaning: sending water to waste lowers the level each time.
- Skimmer and cover habits: a pool without a cover loses more than one that is covered at night.
If the drop is slow and matches hot, windy weather, that is likely normal. Topping up occasionally is part of owning a pool.
The bucket test, step by step
This is the standard way to tell evaporation from a leak. It costs nothing and takes a day of patience.
- Fill a bucket with pool water, to a level a little below the pool’s water line.
- Set it on a pool step, so it sits in the water and gets the same sun and wind as the pool.
- Mark the water level on the inside of the bucket, and mark the pool level on the outside of the bucket.
- Switch the pump off for the test, and do not swim or top up.
- Leave it for a day, then compare. If both have dropped the same amount, it is evaporation.
- If the pool has dropped more than the bucket, you likely have a leak.
To narrow it down, repeat the test with the pump running. If the pool loses more with the pump on, the leak is probably in the plumbing under pressure. If it loses the same either way, think shell, skimmer or fittings.
Where pool leaks usually are
If the test points to a leak, these are the usual suspects, roughly in the order we check them:
- Skimmer box: the joint between the skimmer and the pool shell often moves or cracks over time
- Return and suction fittings: worn seals or loose fittings in the wall
- Light niches: the seal around an underwater light, and its conduit
- Cracks in the shell or surface: especially cracks that run below the water line
- Tiles and the waterline: failed grout and loose tiles let water behind the surface
- Pipework: underground plumbing between the pool and the equipment
A tip: if the level drops and then stops at a certain height, the leak is likely at that level, such as the skimmer or the top of a fitting. That is a useful clue to pass on to whoever looks at it.
What we can repair, and what needs a specialist
We are resurfacing and surface repair people, so we look at leaks that sit in the shell, the surface, tiles and the fittings around the pool. Our pool leak repair page covers how we approach those. Cracks that let water out are covered under pool crack repair.
If the leak is in underground plumbing, you may need a leak detection specialist or a plumber. We will say so plainly if that is what your pool needs, rather than sell you a repair that will not fix it.
Do not drain the pool to find the leak. Emptying a concrete pool without checking the ground conditions and the hydrostatic valve can damage it. See our guide to the hydrostatic valve before you pull the plug.
Ways to cut normal water loss
If the bucket test says it is only evaporation, a few habits keep the level steadier. A pool cover reduces evaporation considerably, and a windbreak or hedge helps on exposed blocks. Keep an eye on how often you backwash, and top up a little at a time rather than letting the level fall well below the skimmer, since a pump that runs dry can be damaged.
When a leak is a sign of a bigger job
A leaking pool with a worn surface is a good time to look at the whole shell, because the fix and the resurface share a lot of the same prep. If you are already seeing roughness, flaking or hollow-sounding render, see our pool resurfacing page, or the signs your pool needs resurfacing. Whatever the cause, book an inspection early so you have time to fix it before you want to swim.
