Is it a leak, or is it evaporation?
Before anyone goes looking for a leak, it’s worth knowing that every pool loses some water. Sun, wind and heat evaporate it, and Sydney summers, especially hot and windy ones, can take a noticeable amount. Splash-out, kids bombing in and backwashing the filter all lower the level too. A dropping water level isn’t automatically a leak.
The honest first step is to find out which one you have. That saves you from paying to chase a leak that isn’t there, and it saves you from ignoring one that is. Our guide why is my pool losing water goes through the usual causes.
The bucket test, explained
The bucket test is the simplest way to separate evaporation from a leak. It works because a bucket of water on the pool step loses water to evaporation at about the same rate as the pool does, but it can’t leak.
- Fill a bucket with pool water to about the height of the pool’s normal level, and set it on a step so the water inside is level with the pool outside.
- Mark the water level inside the bucket and the pool level outside it.
- Leave both alone for a day or so, with the pump running as normal and no one swimming.
- Compare. If the pool has dropped noticeably more than the bucket, you likely have a leak. If both dropped about the same, it’s evaporation.
It’s not perfect, but it’s a good indicator. If the result is close, repeat it with the pump off to see whether the plumbing is involved.
Common leak points
Once it’s clear you have a leak, the question is where. In a concrete pool, the usual suspects are:
- The skimmer box joint. The join between the skimmer and the pool wall is a classic weak point, where movement opens a gap.
- Return and suction fittings. The fittings where pipes meet the shell can loosen or their seals can fail.
- Cracks in the shell. A crack below the waterline leaks, and the leak tends to stop when the water drops to the crack. See our pool crack repair page.
- Light niches. The niche and its seals can leak, and the cable conduit behind it can let water out.
- Failed waterline tiles and edge detail. Water getting behind tiles can find a way out.
A useful clue is where the level stops dropping. If the water stops falling at the skimmer, it may point to the skimmer or fittings. If it stops at the light, look at the light niche. We use that kind of clue to narrow the search before we start testing.
How we find and repair the leak
Narrow it down
We start with what you’ve noticed, and then check the level behaviour, the visible fittings and any cracks. Often this points us straight to the area to test.
Confirm the source
Fittings and joints are tested individually so we aren’t guessing. Dye can show where water is moving through a crack or joint, and it’s a simple, useful tool.
Repair at the source
A shell or surface leak is repaired by opening the problem area, cleaning it and sealing it with the right material, not by smearing sealant over the top. A failed fitting seal or a skimmer joint is reset and sealed properly.
Retest
After the repair we recheck the level to confirm the leak has stopped. Fixing one leak sometimes reveals a second one, which is why we recheck rather than assume.
What we repair, and what needs a specialist
We repair leaks in the shell and surface of the pool: cracks, joints, fittings in the shell, and tiles and edge detail. These are the leaks that sit within the scope of a resurfacing and repair crew.
Some leaks aren’t in the shell. Underground plumbing, such as pipework running between the pool and the equipment, may need a specialist leak detection and plumbing company, with pressure testing and their own equipment. If that’s what your pool has, we’ll say so rather than guess, and we won’t quote for work outside what we do.
Straight advice: if you’ve done the bucket test and it’s evaporation, we’ll tell you, and there’s nothing to repair. If it’s underground plumbing, we’ll point you to the right specialist.
Leaks and resurfacing
If your pool needs a resurface as well, the best time to fix a shell leak is while the pool is empty and the surface is off. The problem areas are exposed, the repair is done on a bare shell, and the new finish goes on top. Chasing leaks one at a time under a new surface is slower and more disruptive.
Don’t empty the pool yourself to look for a leak, especially after heavy rain. An empty concrete pool can lift if groundwater is high. Leave the draining to people who check ground conditions and the hydrostatic valve first. The broader range of repairs is on our pool repairs page.
Book a leak inspection
We inspect first, explain what we find and quote in writing. Pool season opens in November, and a pool losing water is best sorted before then. Booking early gives you the widest choice of dates whether you want to swim by November, Christmas or later in summer. We work across all of Greater Sydney.
