Every pool loses some water to evaporation — but distinguishing normal evaporation from an actual leak is the first question, and it has a straightforward test. This guide covers how to tell the difference, how to identify where a leak is coming from, what professional detection involves, and what repair typically costs.
Normal Water Loss vs. a Leak
A pool without a cover typically loses 1–3 cm (about 0.5–1.5 inches) of water per week to evaporation in summer, depending on sun exposure, air temperature, wind, and humidity. A pool with a cover loses significantly less.
Signs that point to a leak rather than evaporation: losing more than 3 cm per week without a cover (more than 0.5 cm per week with a cover); needing to add water more than once per week; an autofill system running more frequently than normal; wet spots in the yard near the pool or the equipment pad; unusually high water bill; algae problems that recur faster than expected (dilution from fresh water dilutes sanitizer).
The Bucket Test: The Definitive DIY Diagnostic
Before calling a professional, confirm whether the pool is actually leaking with the bucket test.
- Fill a bucket with pool water to approximately 3 cm from the top
- Place the bucket on a pool step, partially submerged, so the water inside the bucket and the pool are at similar temperatures
- Mark the water level inside the bucket (with tape or a marker) and mark the pool water level on the outside of the bucket
- Run the pool equipment normally for 24 hours
- After 24 hours, compare the drop in pool water level to the drop inside the bucket
Reading the result:
- Pool dropped more than the bucket: you have a leak
- Pool dropped about the same as the bucket: normal evaporation; no leak
The diagnostic refinement — run it twice: Run the test once with the pool equipment (pump and filter) running, then repeat with the pump off for 24 hours.
- Pool loses more water with the pump on: the leak is in the plumbing or equipment
- Pool loses about the same with or without the pump: the leak is in the shell, liner, or a gravity-fed component
This two-run test narrows the leak to one of two categories and tells the professional you call exactly where to start looking.
Types of Pool Leaks
Liner Leaks (Vinyl Pools)
The most common leak type in vinyl pools. Small punctures or tears allow water to migrate behind the liner into the surrounding soil.
Where liner leaks most commonly occur: the floor-wall junction; around fitting openings (skimmer face-plate, return jets, main drain); at the bead track; steps and bench areas.
DIY dye test: using a pool dye in a syringe or squeeze bottle, slowly release dye near a suspected area while the pump is off and the water is still. If the dye drifts toward a specific point and disappears into it, you’ve found the leak.
Plumbing Leaks (Underground)
Buried PVC plumbing lines can develop cracks at joints where ground movement has shifted connections. These are typically confirmed by the bucket test showing more loss with the pump running.
Concrete Shell Cracks
Concrete pool shells can develop cracks — surface crazing (fine hairline cracks) is usually cosmetic, while through-cracks allow water to migrate from the pool into surrounding soil. Dye testing near a crack reveals active water movement.
Fitting and Equipment Pad Leaks
Loose or degraded O-rings and gaskets at return jet fittings, skimmer connections, or equipment pad unions. These are visible as dripping or weeping at fittings and usually the simplest to repair.
Professional Leak Detection Methods
Pressure Testing
Each plumbing line is individually pressurized and monitored for pressure drop over 30–60 minutes. A line that loses pressure has a failure point. Confirms whether plumbing is involved and identifies the specific line without requiring excavation.
Dye Testing
A dye injector releases coloured dye near suspected leak areas. If the dye moves toward a specific point and disappears, that’s the leak. Highly effective for liner and fitting leaks, and for confirming suspected concrete shell failures.
Electronic / Sonar Detection
Specialized equipment listens for the sound of water moving through soil, locating an underground plumbing leak to within 30–60 cm without excavation. Used once pressure testing has confirmed which line is failing.
Underwater Camera Inspection
A fibre-optic camera inserted through skimmer or return line openings inspects plumbing interior for cracks, root intrusion, or joint separation.
Cost of Leak Detection in Toronto
| Service | Typical Cost |
| Basic pressure test and visual inspection | $150 – $300 |
| Full professional detection (dye, pressure, electronic) | $300 – $600 |
| Complex underground detection (sonar, camera) | $500 – $900+ |
Detection cost is separate from repair cost. Getting a definitive leak location before excavating or patching is almost always worth the cost.
Repair Options by Leak Type
| Leak Type | Typical Repair Cost |
| Small liner patch (DIY) | $30 – $100 in materials |
| Professional liner patching (minor) | $100 – $350 |
| Liner replacement (extensive damage) | $4,000 – $10,000 |
| Return jet or skimmer fitting replacement | $200 – $500 |
| Underground plumbing leak repair | $500 – $3,000+ |
| Concrete crack injection (hydraulic cement) | $300 – $1,000 |
| Equipment pad fitting or union repair | $150 – $400 |
Frequently Asked Questions
How do I know if my pool is leaking or just evaporating?
The bucket test is the most reliable DIY method. Fill a bucket with pool water, mark both levels, and compare how much each drops after 24 hours. If the pool drops more than the bucket, you have a leak.
What does it mean if my pool leaks more with the pump running?
This typically indicates a plumbing or equipment leak — water is being pushed through a failing joint or fitting under pump pressure.
Can I find a vinyl liner leak myself?
Sometimes — dye testing near suspected areas can locate a liner leak. For leaks that aren’t visually obvious, a professional dye test is more systematic.
How long does professional leak detection take?
Typically 2–4 hours. A complex underground leak requiring sonar and camera work may take a full day.
Is it worth paying for professional leak detection vs. guessing?
Almost always. Excavating the wrong section of plumbing costs more than a detection service; professional detection pays for itself on the first job.
Get a Leak Assessment
Persistent water loss that fails the bucket test warrants professional investigation.
Contact Easy Pools at (647) 449-9512 for a free, no-obligation leak assessment and repair quote.