Pool Leak Detection & Repair
Tell a pool leak from evaporation, then trace it to the pipe, valve or fitting.
Plumbing guide
Pool Leak Bucket Test: How to Do It and Read the Result
Every pool loses water to sun and wind. The bucket test separates normal evaporation from a leak using nothing more than a bucket, a marker and a day of waiting.
By the Urban Comfort Plumbing team ·
Why a pool loses water
Evaporation is the biggest reason a pool level drops. Warm air, low humidity, wind and a sunny surface all speed it up. Pools also lose water to splash-out, backwashing the filter and swimmers climbing out. In a hot climate, evaporation alone can drop the level by roughly a quarter inch a day, and more on a hot, windy day. That is only a rule of thumb, not a limit.
A leak is water escaping the system through the shell, the plumbing or the equipment. A leak keeps going when the weather is cool, calm or humid, and it can run day and night. The bucket test is built on that difference. Evaporation takes water from both a pool and a bucket on the step. A leak only takes it from the pool.
How to run the bucket test
Fill a plastic bucket with pool water until it is about an inch below the rim, and set it on the first or second step so the bucket sits in the water. The water level in the bucket should match the pool level or sit a little below it. Mark the water level inside the bucket with a marker or tape, and mark the pool level on the outside of the bucket at the same spot. American Leak Detection, a leak-detection company, describes the same method: set the bucket on a pool step, mark the water level inside it and the pool level outside it, wait a day, then compare the two marks.
Turn off the automatic fill valve so that the pool is not topping itself up, and do not use the pool during the test. Leave the pump on its normal schedule for the first day. After 24 hours, compare the two marks. Measure how much the pool level dropped against the bucket, using a ruler, not by eye.
How to read the result
If the pool dropped by the same amount as the water in the bucket, the loss is evaporation. If the pool dropped more than the bucket, by about a quarter inch or more, water is escaping from somewhere. The bigger the difference, the larger the leak.
Run the test on a day without rain and without heavy splashing. Rain adds water to both containers, though it adds it unevenly if the bucket is covered or partly shaded. Do not take a single result as final. Repeat it for a second day to confirm.
The pump on, pump off follow-up
If the first test shows a leak, run a second one with the pump off for the whole 24 hours, and compare. If the loss stops or slows when the pump is off, the leak is likely in the pressure side of the plumbing, such as the return lines, a fitting at the equipment pad or a valve. Pressure from the pump pushes water out through a crack that stays closed when the pump is off.
If the pool loses the same amount with the pump off, the leak is more likely in the shell, a skimmer, a light niche or a fitting set in the pool wall. Dye testing, done by squeezing a small amount of dye near a suspected crack and watching whether it is pulled into it, helps point to the spot.
Other clues to check yourself
Look at the equipment pad. Wet ground around the pump, filter or heater, or water dripping from a fitting, is easy to spot. Check the skimmer basket area for cracks. Look at the water line tile for cracks or gaps. Watch the ground around the pool and the deck, including a soggy patch in the lawn that stays wet on a dry week. Look at the autofill device too. A fill valve that sticks open can add water as fast as a leak removes it and hide the problem, and it also raises the water bill.
Pay attention to the water bill. If the household bill climbs while nothing else in the house has changed, a pool leak is a candidate. A meter test with the pool fill turned off helps rule the house in or out. See leak detection for how that works.
Common mistakes that spoil the result
The most common error is letting the pool top itself up during the test. An autofill valve will quietly refill the pool and cancel the loss you are trying to measure. Switch it off first. A second mistake is placing the bucket on the deck, where it sits in the air. The bucket must sit in the pool so that both containers see the same sun and temperature.
Do not run the test right after a storm or a heavy swim party, when splash-out and rain make the numbers unreliable. And do not trust a result from a bucket that is half full of water at a different level than the pool, since a deep bucket and a shallow one lose water at slightly different rates. Keep the starting levels close.
Keeping a log
Write down the date, the pool level and the weather each day for a week. A simple record makes the pattern clear. If the level drops by a steady amount every day, no matter the weather, that points to a leak. If the drop tracks hot, windy days, evaporation is the likely cause. The log is also useful for the contractor, who will ask how fast the pool is losing water and when you first noticed.
What to do next
Stop adding chemicals to a pool that is losing a lot of water, since the chemicals go with it. If the pool drops fast, turn the pump off before the water level falls below the skimmer, to avoid running it dry. If you can see water surfacing in the yard, call for help quickly.
A pool leak detection visit isolates each plumbing line with pressure tests, checks the shell and fittings and finds the location. Repairs range from replacing a fitting to digging up a section of line. Ask how the deck will be restored and whether the pool will need to be drained.
Common questions
Pool leak test questions
It depends on sun, wind and temperature. About a quarter inch per day is a common rule of thumb in warm weather, but the bucket test compares your pool against a bucket in the same conditions.
Run the test once with the pump on, then again with it off. The difference helps show whether the leak is on the pressure side or in the shell.
Rain adds water to both the pool and the bucket, but not always evenly. Pick a dry day, and repeat the test if it rains.
It can, because you refill what escapes. If your bill rises with no other change, ask about a leak search.
Related services
Leak Detection
Find a hidden leak behind a wall, under a floor or between the meter and the house.
Water Line Repair & Replacement
Repair or replace the pipe that carries water from the meter into the house.
Pool dropping faster than the bucket?
Call and give the test result. It helps the contractor plan the visit.