Pool Leak Detection: How to Find and Fix Leaks

2024-12-05

A pool that needs the hosepipe every few days is costing you in water, chemicals and, eventually, damage to the ground around it. But a Highveld pool also loses a surprising amount of water to evaporation, particularly in hot, dry and windy weather, and that is perfectly normal. This guide shows you how to tell the two apart, where leaks usually are, how they are found, and what fixing them involves.

How much water loss is normal for a pool?

There is no single number, because evaporation depends on the weather. Heat, low humidity and wind all increase it, and Gauteng has plenty of all three: summer heat, very dry winter air, and the windy weeks of August and September. Splash-out, backwashing and water features add to the loss, and a pool cover reduces it considerably. Rather than compare your pool with a neighbour's, test it against itself with the bucket test.

How do I do the bucket test?

The bucket test compares your pool with a bucket of the same water, in the same sun and wind. It takes a day or two.

Fill a bucket with pool water to a few centimetres below the rim.
Stand it on the top step, so it sits in the pool at the same temperature.
Mark the water level inside the bucket, and mark the pool's level on the outside of the bucket (or on the weir or a tile).
Switch off any automatic top-up, and do not swim or backwash during the test. Run the pump as normal.
After 24 to 48 hours, compare the two drops.
Repeat the test with the pump off for the same length of time.

Reading the result:

The pool and the bucket dropped by about the same amount: that is evaporation.
The pool dropped clearly more than the bucket: you have a leak.
The pool loses more with the pump running than with it off: the leak is probably in the plumbing that is under pressure when the pump runs.
The pool loses about the same either way: suspect the shell, a fitting or the light niche.
The level always stops falling at the same point — the bottom of the weir mouth, or the light — which is a strong clue to where the leak is.

Where do pool leaks usually happen?

Most leaks turn up in a handful of predictable places:

The weir, where it joins the pool shell. Ground movement cracks that joint.
The light niche, through the conduit and seal behind an underwater light.
Return fittings and aimflows, where they pass through the shell.
Cracks in the shell, especially in older pools and on clay soils that swell in wet summers and shrink in dry winters.
The multiport valve, when a worn gasket sends water down the backwash line even on Filter — one of the most common "leaks", and one of the cheapest to fix.
Pipe joints at the pump and filter, and the underground pipe runs between the pool and the equipment.

Can I find a pool leak myself?

You can often narrow it down. With the pump off and the water still, release a little leak-detection dye (or food colouring) close to a suspected crack or fitting and watch whether it is drawn towards it. Check the equipment area for damp soil or drips, look into the backwash sight glass or line to see whether water is flowing to waste when it should not be, and walk the garden between the pool and the pump for wet patches that never dry, soft ground or sinking paving.

How do professionals find pool leaks?

We start with the equipment, because a worn multiport gasket or a dripping joint at the pump is visible once you know where to look. If the equipment is sound, we move to the pool itself: dye testing around the weir mouth, the light niche, the returns and any visible cracks. Where the pump-on and pump-off results point to the plumbing, the lines are isolated and checked one at a time to narrow the leak down to a section of pipe. The result is a location and a recommendation, not a guess.

Our leak detection is R1,200, and you get a clear answer about where the leak is and what fixing it involves before you commit to any repair.

How are pool leaks repaired?

Most repairs are straightforward once the leak has been found:

Weir cracks can be sealed, or the weir replaced if it has pulled away from the shell.
Light niche seals can be redone.
Return fittings can be resealed or replaced.
Small shell cracks can be patched with a suitable underwater or pool-surface repair compound.
Multiport gaskets are replaced.
Pipe leaks mean opening the ground at the right spot, which is why locating them accurately matters so much.

Some shell repairs need the water lowered below the crack, and a few need the pool empty. Where a repair needs draining, we plan it for the dry winter months where possible, for the same ground-pressure reasons that make winter the season for acid washes. If the pool is being drained anyway, an acid wash and the repair can be done together. Repairs are quoted in writing and done only with your go-ahead; our pool repairs page covers weirs, lights, valves and fittings. If you want a repair looked at on its own, a call-out is R650, deducted from your quote when you accept it.

What does a leak cost if I ignore it?

A slow leak is easy to live with and expensive to keep. Every litre that leaves the pool is replaced with fresh municipal water that needs chlorine, pH correction and stabiliser, so the chemical bill climbs along with the water bill. The escaping water has to go somewhere, and over months it can wash out the ground under paving or around the shell, turning a small repair into a big one. A leak on the suction side costs filtration instead: air gets in, the pump loses prime, and the pool gets harder to keep clear.

How do I prepare for a leak detection visit?

Do the bucket test with the pump on and again with it off, and write down how much each dropped over how many hours.
Note whether the level stops falling at a particular point.
Keep the water clear and at its normal level; dye testing needs visibility and a full pool.
Switch off any automatic top-up for the test period.
Tell us about recent work on the property. New paving, a tree removed near the pool, building work or earth-moving can all disturb pipes and shells.

We find leaks across Centurion, Pretoria East, Pretoria and Midrand.

Frequently asked questions

Why is water always coming out of my backwash pipe?

The multiport valve's internal gasket is usually worn, so water leaks to waste even on Filter. It is a common fault and usually a quick repair.

Does a pool leak show up when it rains?

Rain hides a leak by topping the pool up. Do the bucket test in a dry spell.

Will a pool cover help with water loss?

With evaporation, considerably. It will not stop a leak, so do the bucket test first.

Should I keep topping the pool up until the leak is found?

Yes. Keep the level at least halfway up the weir opening so the pump does not suck air, but note how much you add — that is useful evidence.

Talk to us

WhatsApp or call Crystal Reef on 081 577 5051 with your bucket-test results, or email sales@crystalreef.co.za. For the bigger winter job that often goes with a leak repair, read acid washing your pool.