Stop blaming evaporation for your pool water loss
A few centimetres a week. You top it up and blame the heat. Four months later the backfill has been wet the whole time.
Key takeaways
- A bucket test costs nothing and separates evaporation from a real leak in three days.
- Plumbing lines and fittings cause most leaks. The shell is the least likely source.
- The most common causes are also the cheapest to fix, which is why testing before quoting matters.
- Surface crazing in plaster holds water fine and gets blamed for leaks it did not cause.
- Shutting circulation off for 24 hours tells you whether the loss is plumbing or structure.
- Constant top-ups dilute chemistry, so you buy chemicals all year to cover a leak.
- Saturated backfill pushes on the shell walls, turning a plumbing repair into a structural one.
- Most leaks are found without demolishing decking, so a jackhammer should never be step one.
What Is Swimming Pool Leak Detection? Unpacking the Myths
The water drops a few centimetres a week. You top it up, tell yourself it is the heat, and top it up again. Four months later the backfill around the shell has been wet the entire time and the problem is no longer about water.
Swimming pool leak detection means isolating where water leaves the system before anyone breaks concrete. It is a process of elimination, and it costs almost nothing compared with the repairs people authorise without it.
The Difference Between Evaporation and a Leak
Philippine heat evaporates real water, and owners use that to explain away genuine leaks for months. The bucket test settles it. Fill a bucket with pool water, set it on a step so it sits at the same temperature and sun exposure, mark the level inside and outside, then compare the drop after three days.
Equal drop means evaporation. If the pool falls faster, water is leaving through something. That test costs nothing and it stops you from paying for a diagnosis you can run yourself.
Where Pool Water Actually Escapes
Four places, roughly in order of how often we find them. Plumbing lines and their fittings come first, particularly returns and suction lines under the deck. Skimmer throats crack where the plastic meets concrete. Light niches and their conduit leak around the seal. The shell itself comes last, and even then the crack usually sits at a transition wall rather than in the floor.
Notice what that order means for pricing. The cheapest repairs are also the most likely, which is exactly why a contractor should test before quoting.
Common Misconceptions: The Truth Behind Finding a Pool Leak
The belief that costs the most: visible cracks are the leak. Hairline crazing in plaster is common, mostly cosmetic, and frequently blamed for water loss that is coming from a return line six metres away.
Does a Crack Always Mean the Shell Failed?
No. Surface crazing sits in the finish, not the structure, and it holds water fine. Structural cracks run deeper, often follow the transition between wall and floor, and usually come with movement you can see over time. Telling them apart takes an inspection, not a photograph.
We get called to pools where an owner has already paid for shell injection, and the water was leaving through a cracked skimmer the whole time.
What a Proper Leak Investigation Includes
- A pressure test on each plumbing line separately, with written results per line rather than a single pass or fail
- Isolation testing that shuts off the circulation to see whether loss continues, which separates plumbing from structure
- Physical inspection of skimmer throats, return fittings, light niches, and main drain
Any contractor who quotes structural repair without those three has guessed. Ask which lines they tested and what the results were.
How Long Detection Should Take
Most investigations resolve within a day or two on site. Nobody needs to demolish decking to find a leak in the majority of cases, and a contractor who reaches for a jackhammer first is skipping the part that protects your budget.
Get the results in writing before you approve any repair.
The Financial Impact of Ignoring a Pool Leak
A slow leak looks affordable because you only see the water bill. The real cost accumulates out of sight.
- Every top-up dilutes your chemistry, so chlorine, stabiliser, and balancing chemicals get consumed faster all year
- Saturated backfill loads the shell walls from outside, which converts a cheap plumbing repair into structural remediation over time
- Continuous moisture around light conduit and bonding creates an electrical problem alongside the water one
A leak is never just water. It is chemistry you keep re-buying, backfill that keeps pushing on your walls, and a repair that gets more expensive every month you wait.
Your Next Move This Week
- Run the bucket test for three days and write down both measurements. You now have evidence rather than a suspicion.
- Turn the circulation off for 24 hours and measure again. If the loss slows, your leak is in the plumbing.
- Call for a pressure test, not for a quote. The quote should come after the diagnosis, never before it.
Repairing a Pool Leak and Preventing the Next One: What You Need to Know
You have located the leak. What happens next determines whether you do this again in three years.
Why Specialist Repair Matters Here
Use a pool contractor rather than a general plumber, for three reasons. They repair lines to pool service conditions, which involve constant pressure and chemically treated water. They re-establish waterproofing at any penetration they open. And they pressure-test again after the repair, before anything gets covered.
Warning Signs You Have a Leak Right Now
- Water loss beyond a couple of centimetres a week in a covered pool
- Ground that stays soft or unusually green near one section of the deck
- Chlorine demand climbing month after month with no change in use
- Tiles lifting or grout washing out in one localised area
- Air bubbles returning through the inlets when the pump runs
Keeping the Repair Sound
- Ask for the post-repair pressure test results in writing
- Record water level weekly for the first two months so you can prove the fix held
- Keep chemistry balanced, since aggressive water attacks fittings and grout
- Never drain the pool without checking groundwater conditions first
Find it before you fix it, and the repair stays cheap.
Part of our guide to pool renovation in the Philippines. Related: pool water treatment in a tropical climate. If a contractor walked off mid-build, read how to take over an abandoned pool.
Frequently asked questions
How do I check if my pool is leaking?
Run a bucket test over three days. Fill a bucket with pool water, sit it on a step so it shares the same sun and temperature, mark the level inside and outside, then compare the drop. Equal drop means evaporation. A pool falling faster than the bucket has a leak.
Where do most swimming pool leaks come from?
Plumbing lines and fittings account for most of what we find, followed by skimmer throats and light niches. The shell itself is the least common source. That order matters because the most likely causes are also the cheapest to repair, which is why testing before quoting protects your budget.
How much water loss is normal?
Evaporation varies with heat, wind, and whether the pool is covered, so measure it against a bucket rather than against a rule of thumb. Loss beyond a couple of centimetres a week in a covered pool warrants investigation.
Can you find a leak without breaking the deck?
In most cases, yes. Pressure testing each line separately and isolating circulation narrows the location without demolition. A contractor reaching for a jackhammer before testing is skipping the step that keeps the repair affordable.
Does a crack in my pool mean it is leaking?
Not necessarily. Fine surface crazing sits in the plaster finish and usually holds water. Structural cracks run deeper and often follow the transition between wall and floor. Only an inspection tells you which one you have.
How long does leak detection take?
Most investigations resolve within a day or two on site, including pressure testing and physical inspection of fittings. You should receive written results per line before approving any repair work.
Will ignoring a small leak cause bigger problems?
Yes. Constant top-ups dilute your chemistry so you buy more chemicals all year, and saturated backfill loads the shell walls from outside. A cheap plumbing repair left alone becomes structural remediation.
Should I use a plumber or a pool contractor?
A pool contractor. Pool plumbing runs under constant pressure with chemically treated water, and any penetration opened during repair needs waterproofing re-established. A general plumber will not restore that detail.
Planning a pool? Talk to the engineering team.
Send the site details and the intended use, and we will come back with a technical assessment and a costed proposal.