You notice that your pool’s level is dropping faster than usual. Before imagining the worst and booking a leak detection, ask yourself the right question: is it really a leak, or simply evaporation amplified by high temperatures?
A residential in-ground pool loses between 0.5 and 2.5 cm of water per week from evaporation in summer, sometimes more during a heat wave, in strong wind or if it isn’t covered. If you exceed 5 cm of weekly loss without rainfall, or if you notice soggy ground around the pool, you probably have a real leak. The bucket test lets you settle the matter in 24 hours without having to call a professional.
What level of evaporation is normal in summer?
Evaporation depends on four factors: air temperature, water temperature, humidity and wind. Here are some orders of magnitude observed for the Quebec climate:
| Conditions | Weekly evaporation |
| Normal season (June, September) | 0.5 to 1.5 cm |
| Hot summer without wind | 1.5 to 2.5 cm |
| Heat wave (>30 °C for several days) | 2.5 to 4 cm |
| Heat wave + strong wind + uncovered pool | up to 5 cm |
If your losses fall within these values, it’s evaporation. If you exceed these thresholds without an extreme heat wave, it’s a signal to investigate further.
The factors that amplify evaporation
Four situations that explain greater evaporation than expected, without there being a leak:
- Prolonged heat wave: each degree above 30 °C accelerates evaporation.
- Persistent wind: a wind at 20 km/h can double the evaporation rate compared with a calm day.
- No solar cover: a pool left uncovered at night loses more water than a covered pool. Our article on the benefits of a solar cover details these savings.
- Heavy use: the splashing generated by an active family loses more water than you’d imagine, easily 1 to 2 cm per week in high season.
The bucket test: the method to settle it in 24 hours
The bucket test, or plug test, lets you isolate evaporation and measure it independently. Here are the five steps to remember:
- Prepare a bucket. Take a standard 5- to 10-litre bucket and fill it three-quarters full of water.
- Place it in the pool. Set it on the first step, weighted down if needed. The water in the bucket and the pool water should reach the same level, on the inside. Mark these two reference points with a felt-tip pen on the walls of your container.
- Turn off the pump. During the test, the filtration must be off. Cover the pool if possible.
- Wait 24 hours. Without rain, without using the pool and without filtration.
- Compare the two levels. If the bucket water and the pool water have dropped to the same level, it’s normal evaporation. If the pool water has dropped more than the bucket’s, you very likely have a leak.
- Then redo the test over a new 24-hour period, this time with the pump running. If the loss is greater when the pump is running, the leak is probably in the plumbing or the return jets. If it stays constant whether the pump is running or not, the leak likely comes from the structure or the liner.
The signals of a real leak
Beyond the bucket test, certain signals don’t lie:
- Spongy or soggy ground around the pool, especially if it occurs in a single spot
- A level dropping rapidly and steadily (more than 5 cm per week without a heat wave)
- A pump that loses prime regularly
- Air in the piping when the pump starts up
- Settling, cracks or sinking of the pool surround
When to entrust the situation to a specialist
If the bucket test confirms a leak, the next step is detection. A leak can come from several sources: a punctured liner, a cracked skimmer gasket, a crack in the structure, a worn plumbing fitting, a leaking return jet. A specialist has tools you don’t have at home: an underwater camera, tracer gas, an underwater microphone for buried plumbing. Detection costs a fraction of the price of a leak ignored for a season.
The costs of an ignored leak
Letting a pool leak for a full season isn’t just a matter of having to fill it more often. The real problems show up afterward:
- Erosion of the soil and foundations under and around the pool
- Sinking of the surround which becomes unstable
- Plumbing damaged by the continuous runoff
- Salt system or heating cell damaged by insufficient flow
- A liner that loosens or tears more quickly from loss of support
A leak spotted early typically costs between $200 and $800 to diagnose. A leak ignored for two seasons can cost several thousand dollars in structural repairs.
“The leak no one sees is the one we find three seasons later, when the surround has started to sink. If we’d stepped in six months earlier, it could have been a simple repair. Now it’s the whole landscaping that has to be redone. That’s why we take the calls seriously from the very first abnormal drop in the water level.”
– Tristan Dufour, owner and pool expert, Piscine Évolution
Do you suspect a leak? Act before it gets worse. The bucket test gives you a clear answer in 24 hours. If the result points to a leak, or if you see the signals described above, a targeted professional diagnosis avoids unpleasant surprises and protects your investment. Our team uses the detection tools suited to each type of leak, explains exactly what it found and what that means, and proposes a repair sized to the problem, no more. Request an estimate for leak detection, and act before the first signs turn into real damage.
