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Is My Pool Leaking? The Bucket Test
Reviewed by the Devon Leak Detection team. Last updated June 2026
The short answer: A bucket test tells you whether your pool is losing water to normal evaporation or a genuine leak. Float a bucket of pool water on the steps, mark both levels, and check after 24 hours. If the pool drops faster than the bucket, you most likely have a leak worth investigating.
Every swimming pool loses a little water. On a warm, breezy Devon afternoon, an open pool can shed a surprising amount through evaporation alone, and that is completely normal. The trouble is that evaporation and a slow leak look identical from the poolside: the water level just keeps creeping down. Before you start worrying about cracked pipes or a failing liner, there is a simple, free test that separates one from the other. It is called the bucket test, and you can run it this weekend with nothing more than a clean bucket and a marker pen.
Why pools lose water in the first place
Evaporation is driven by temperature, wind, humidity and how much of the surface is exposed. Warm water, dry air and a stiff breeze all speed it up, which is why losses often look worse in a sunny spell. A heated pool left uncovered overnight can also give up more water than you might expect, because warm water evaporates faster than the cooler air above it.
A leak, by contrast, does not care about the weather. It loses water steadily whether it is sunny or pouring with rain. That difference is exactly what the bucket test is designed to expose. By placing a bucket of pool water in the same conditions as the pool itself, you give evaporation an identical playing field. Whatever the bucket loses is roughly what the pool should lose to evaporation too. Anything beyond that points to a leak.
How to run the bucket test, step by step
The whole point of the test is to compare like with like, so keep things simple and consistent.
- Fill a bucket with pool water. Use a clean bucket and fill it to within an inch or two of the rim. Using pool water rather than tap water keeps the temperature matched, so both bodies of water evaporate at the same rate.
- Stand it on a step. Place the bucket on the first or second step of the pool, so it sits partly submerged. Weigh it down with a brick or stone if it wants to float. The aim is to expose the bucket to the same sun, wind and air temperature as the pool.
- Mark both water levels. Using tape or a waterproof marker, mark the water level inside the bucket and the pool level on the outside of the bucket. Now you have two reference points moving in the same conditions.
- Leave it for 24 hours. Run the pool exactly as you normally would, and leave the cover off so both the pool and the bucket are exposed. A cover would slow evaporation in the pool but not the bucket, which would throw the result off.
- Compare the two marks. After a full day, look at how far each level has dropped. If the pool and the bucket have fallen by roughly the same amount, you are simply seeing evaporation. If the pool has dropped noticeably more than the bucket, water is escaping somewhere and a leak is likely.
For the clearest result, try to run the test on a settled day rather than during heavy rain, which adds water back into both the pool and the bucket and muddies the comparison. If you can, repeat the test over two cycles to be confident in what you are seeing.
Pump on, pump off: narrowing it down
If the first test points to a leak, you can learn a little more by running it twice: once with the filtration pump running and once with it switched off. The plumbing behaves differently under pressure, so the comparison can hint at where the problem sits.
If the pool loses more water with the pump running, the leak may be on the pressure side of the system, such as the return lines that push water back into the pool. If it loses more with the pump off, suction-side plumbing or the pool structure itself may be the culprit. This is not a precise diagnosis, but it gives a useful steer and saves time when a professional comes to investigate.
Signs you might notice alongside falling water:
- Constant top-ups, or an automatic filler that seems to run far more than it used to
- A creeping rise in your water bill with no obvious explanation
- Soft, boggy or mushy ground around the pool, or patches of lush grass when it has not rained
- Air bubbles or spluttering from the return jets, or gurgling in the pipework
- Visible cracks in the shell, tiles or surround, or a damp area on a nearby wall
What the warning signs are telling you
Each of those clues points in a slightly different direction. A constantly topping-up pool is the most common giveaway, especially if an automatic filler has been quietly masking the loss for weeks. Wet or unusually green ground often suggests a buried pipe is leaking underground, since the escaping water has to surface somewhere. Air being pulled into the returns usually means there is a gap on the suction side, where the system is drawing in air through the same fault that lets water out. Reading these alongside your bucket test result helps build a fuller picture before anyone lifts a paving slab.
How pool leaks are professionally located
The bucket test confirms that water is going somewhere, but it cannot tell you exactly where. That is where non-invasive leak detection comes in. The goal is always to find the precise point of failure without digging up the whole garden, and several techniques are used together to do it.
Dye testing is a simple but effective method for the shell and fittings. A small amount of coloured dye is released near a suspected fault below the waterline, and if water is escaping there, the dye is visibly drawn towards the crack or gap. It is commonly used around skimmers, main drains, light fittings and return inlets.
Pressure testing is how the underground plumbing is checked. Each line is isolated and pressurised in turn. A pipe that cannot hold pressure has a fault, which tells the technician precisely which line to focus on rather than guessing across the whole system.
Acoustic listening equipment then pinpoints the spot. Sensitive microphones pick up the faint sound of water escaping from a pressurised pipe, even when that pipe runs beneath a patio, decking or a thick concrete surround. By tracing where the sound is loudest, a leak can often be located to within a small area, keeping any eventual repair as contained as possible.
In practice these methods are combined, usually starting with a visual inspection and the clues you have already gathered, then moving through pressure and acoustic work to confirm the exact location. If you have run a bucket test and noticed any of the warning signs above, our swimming pool leak detection service can take it from there. You can also explore the areas we cover across Devon, or browse more guidance in our articles.
Frequently Asked Questions
There is no single figure, because evaporation depends on the weather, water temperature and how exposed your pool is. That is exactly why the bucket test is so useful: instead of chasing a number, it compares your pool against a bucket in identical conditions, so any extra loss in the pool stands out clearly as a possible leak.
No. Leave the cover off for the full 24 hours. A cover slows evaporation from the pool but not from the bucket, which would make the pool look like it is leaking when it is not. Keeping both exposed to the same sun and wind is what makes the comparison fair and reliable.
It can, as long as you fill the bucket with water straight from the pool so the temperatures match at the start. Warmer water evaporates faster, so using cold tap water would skew the result. For the most dependable reading, run the test on a settled day and consider repeating it over a second 24-hour cycle.
The next step is to find exactly where the water is escaping. A professional will typically combine a visual check with dye testing on the shell and fittings, pressure testing of the plumbing and acoustic listening to pinpoint the spot. These methods are non-invasive, so the leak can usually be located without disturbing the whole pool surround.
Yes, and it often is. Running the bucket test with the pump on and then off can hint at whether the loss is on the pressure side, the suction side or the structure. Buried pipework faults are common and frequently show up as soft, wet ground nearby. Pressure and acoustic testing are the usual ways to confirm a plumbing leak.
Lost the bucket test? Let us find the leak
If your pool is dropping faster than the bucket, our team across Devon can pinpoint the source without tearing up your garden. Get in touch for a no-obligation chat.