Pool leak detection: find it, confirm it, fix it properly

Is it evaporation or a leak?

The first thing to rule out is evaporation — because Adelaide's dry summers can pull more water out of a pool than most people realise. Typical losses in our climate:

• Summer peak (uncovered): 3–8mm per day, which is roughly 2–5cm per week
• Summer (pool cover on): less than 1cm per week
• Winter: typically 0.5–2mm per day, or under 1.5cm per week
• Windy days — wind accelerates evaporation significantly, especially on uncovered pools

If you're losing more than that, something is wrong. But evaporation is so variable that eyeballing it isn't reliable. The bucket test rules it out completely.

How to do the bucket test (the DIY standard)

The bucket test is the foundation of pool leak detection. It's free, takes 24 hours, and it gives you a definitive answer on whether you have a leak. Here's how to do it properly:

1. Get a clean 10L plastic bucket. A standard mop or paint bucket is fine. The bucket must not leak itself — check before you start.
2. Place it on the top step of the pool so it sits partially submerged. The water inside and the pool water should be at the same level.
3. Fill the bucket with pool water to match the pool level as closely as possible. Both should be at the same height.
4. Mark the water level inside the bucket (with a permanent marker, piece of tape or waterproof pencil) and the pool level on the outside of the bucket.
5. Turn the pump offand leave everything alone for 24 hours. Don't swim, don't top up, don't run equipment.
6. Come back and measure both drops. Evaporation affects the bucket water and pool water equally, so both should drop the same amount.

If both drop the same amount, there's no leak — it's just evaporation.
If the pool drops more than the bucket, the difference is your leak rate.

Where pools actually leak

In our 30 years of assessing Adelaide pools, here's roughly where we find leaks — in order of frequency:

1. Pool light housings (very common)

Pool lights are the single most common source of small to medium leaks. Underwater light niches develop cracks and seal failures, and the conduit behind the light becomes a direct path for water to escape. If your leak slows or stops when the water level drops below the light, that's your answer.

2. Skimmer boxes (very common)

Skimmers sit where the pool shell meets the hardscape, and they're a classic weak point. Common failures: a crack in the skimmer throat, a broken seal between the skimmer and pool wall, and cracking where the concrete deck meets the box. If your leak stops at skimmer throat level, there it is.

3. Return jets & fittings

The plastic fittings where water returns to the pool age out, especially in older pools. Pressure-side leaks under the pool deck often trace back to a cracked return fitting or loose threads.

4. Underground plumbing

Pool plumbing under the deck is usually the most expensive leak to find and fix. Typical failures: elbow joints where PVC was glued poorly 20+ years ago, pipes that have been compressed by ground movement, or cracked suction lines under skimmer boxes. Professional leak detection services use helium or dye injection to pinpoint these.

5. Cracked shell (concrete & fibreglass)

Ground movement, reactive clay soils (common in Adelaide), tree roots and foundation issues can all crack a concrete pool shell. Fibreglass pools can develop stress cracks around fittings or at high-stress points. Surface cracks in pebblecrete are usually cosmetic, but cracks that go through to the shell are real leaks.

6. Coping seam

The seam between coping and pool shell should be sealed with pool-grade mastic. When it fails, water wicks behind the coping and can leak surprisingly fast. See our pool coping repair page for the fix.

How professional leak detection works

If you've confirmed a leak and can't find it yourself, professional leak detectors use a few techniques:

• Pressure testing plumbing — they isolate each line, pressurise it, and watch for pressure drops. Very effective for finding plumbing leaks without digging.
• Dye testing — colour is injected near suspected leak points and watched with a dive mask. Slow at large scale but reliable for fittings.
• Listening gear (geophones) — amplified listening to hear water escaping under concrete. Works best on plumbing leaks.
• Helium injection — helium is injected into pool lines and traced to the surface with a sniffer. Very precise for buried plumbing.

Professional leak detection in Adelaide typically costs $300–$600 for a call-out and inspection, and another $500–$3,000+ for repairs depending on what they find and whether they need to excavate. For older pools, we often find it's more cost-effective to go straight to restoration rather than chase a leak, fix another, and find a third six months later.

When leaks mean it's time for restoration or resurfacing

A single leak in a sound pool — especially at a light or fitting — is worth fixing in isolation. But when leaks are the tip of the iceberg, we usually recommend a full restoration. The telltale signs that it's a restoration-level problem, not a one-off repair:

• You've had two or more leaks repaired in the last few years
• The surface is rough, pitted or showing delamination
• The pool is 20+ years old and has never been fully resurfaced
• Cracks are visible in the shell, not just the surface coating
• The coping is cracked or lifting off the pool shell
• Skimmer boxes and fittings are original and visibly tired

At this point you're trying to patch a pool that's systemically worn out. Full pool restoration addresses structural cracks, worn fittings, old plumbing, failing coping and the surface all in one project — and resets the pool for another 15–25 years of reliable service.

The water bill side of the conversation

A leaking pool can waste an enormous amount of water. A 1cm-per-day leak on a typical 40,000L pool is 280L of water every day — almost 100,000L a year. At Adelaide water prices and with the environmental cost in a dry state, ignoring a leak gets expensive fast. It also accelerates surface wear, destabilises the ground around the pool, and can cause hardscape damage. It's rarely worth putting off.

Related problems

Pool leaks rarely travel alone. Worth checking if you also have any of these:

• Pool surface peeling — delamination often creates entry points for water escape through the shell.
• Rough pool surface — aged, porous surfaces are usually accompanied by structural issues.
• Pool resurfacing cost guide — what a full fix looks like in 2026 Adelaide pricing.