Bucket Test: Is your pool losing water or is it evaporation?

Data updated in September 2026 — Information verified with internal data from Telefuga and real reviews from Google Maps.

Is your pool losing water or is it evaporation? The definitive answer

If your pool loses more than 6-8 mm of water per day in summer (or more than 2-3 mm in winter), you probably have a leak. But before calling a professional, there is a simple and surprisingly reliable DIY method you can do yourself: the bucket test (also known as the “bucket test”).

At Telefuga, we have been specializing in leak detection in pools for 16 years, with over 8,050 pools repaired in Murcia, Alicante, Valencia, Albacete, and Almería. We have seen owners who drained and replaced the entire tile “just in case” without locating the leak, and others who filled water daily assuming it was evaporation when in reality they were losing hundreds of liters due to an invisible crack in the return pipe.

This article will teach you how to properly perform the bucket test, interpret the results according to your province and the time of year, and know when the test is not enough and you need professional detection.

How to perform the bucket test step by step

The bucket test compares the evaporation of water from the pool with the evaporation of water from a bucket placed inside it. If both lose the same amount of water, the loss is due to evaporation. If the pool loses more than the bucket, you have a leak.

Step 1: Choose the right moment (5 minutes)

Perform the test on a day with stable weather, with no forecast of rain or strong winds. Ideally, choose a period of 24-48 hours with similar weather conditions. Wind is the factor that most distorts the results, as it accelerates evaporation unevenly between the bucket and the pool.

Best time: A Tuesday to Wednesday during the week, when the pool is not in use. Avoid weekends and holidays.

Step 2: Prepare the pool (10 minutes)

• Fill the pool to its normal operating level
• Deactivate the automatic filling system if you have one — this is the most common mistake and completely invalidates the test
• Turn off the pool cleaner robot
• If your pool has a fountain, waterfall, or any element that moves water, turn it off
• Keep the filter running in its normal cycle (the leak could be in the filtration circuit and only manifests with the pump running)

Step 3: Prepare the bucket (10 minutes)

• Use a plastic bucket of at least 15 liters (metal buckets can alter the water temperature)
• Fill it with water from the pool to about 5-8 cm from the edge
• Place it on the first step of the pool ladder, partially submerged. The goal is for the water in the bucket to be at the same temperature as that of the pool
• Important: Do not fully submerge the bucket. It should float partially or rest on the step with the edge above the water level
• If you do not have a ladder, you can place the bucket on the edge of the pool, but the results will be slightly less accurate

Step 4: Mark the levels (5 minutes)

• With waterproof tape or a permanent marker, mark the exact water level inside the bucket
• Also mark the water level of the pool at the skimmer or on a tile of the pool wall. You can use waterproof tape or a wax pencil
• Telefuga Tip: For greater precision, use a millimeter ruler glued with silicone to the inside of the bucket and to the skimmer

Step 5: Wait 24 hours (24 hours)

• Do not use the pool during the test — no swimming, water games, or hoses
• Do not add water under any circumstances
• Do not cover the pool or the bucket with a tarp or cover (both must be exposed to the same conditions)
• If it rains during the test, discard it and start over
• You can extend the test to 48 hours for greater precision

Step 6: Measure and compare (10 minutes)

After 24 hours, measure the drop in water level in the bucket and in the pool:

Telefuga Data: Of the pools we inspected where the owner had correctly performed the bucket test and detected a difference, 92% actually had a leak. A well-executed bucket test is quite reliable as a first diagnostic filter.

Normal evaporation by province and month: reference table

Evaporation depends on temperature, relative humidity, wind, and solar radiation. These are the indicative figures of daily loss due to evaporation in a standard uncovered pool (8x4 m, without cover) in our 5 service provinces:

How to use this table: If your pool in Murcia loses 12 mm/day in July and the table indicates a maximum of 8 mm, those 4 mm of difference represent a leak. In a standard 8x4 meter pool (32 m²), each millimeter of level equals 32 liters of water. That is, 4 extra mm means a loss of 128 liters daily due to a leak.

Quick conversion: millimeters to liters

Factors affecting the evaporation of your pool

Before concluding that your pool has a leak, consider these factors that can significantly increase evaporation:

1. Wind

Wind is the number one factor that accelerates evaporation. An exposed pool can evaporate twice as much as a protected one. In windy areas like the Campo de Cartagena (Murcia) or the coast of Almería, evaporation losses can exceed 10 mm/day in August with westerly winds.

2. Water temperature vs air temperature

The greater the difference between the water temperature and the air temperature, the greater the evaporation. Heated pools or those with heat pumps lose more water due to evaporation than unheated ones, especially on spring and autumn nights when the air cools but the water remains warm.

3. Relative humidity of the environment

A dry environment evaporates more water. Albacete, with an average relative humidity of 55-60% in summer, generates more evaporation than the coast of Alicante (65-75%). This is why the table shows higher values for Albacete in July-August despite being inland.

4. Use of a cover

A pool cover reduces evaporation by between 80% and 95% depending on the type. If you use a cover at night and your pool continues to lose water significantly, the likelihood of a leak is very high. This is, in fact, one of the complementary tests we recommend at Telefuga.

5. Surface area of the water sheet

The larger the surface area, the greater the evaporation in absolute volume (although the rate per square meter may be the same). A 12x6 m pool loses 4 times more liters than a 6x3 m pool with the same evaporation rate.

6. Fountains, waterfalls, and jets

Any element that stirs the water surface or projects it into the air drastically increases evaporation. A waterfall running for 8 hours a day can add an additional 30-50% loss due to evaporation.

Other signs of leaks in pools (besides water loss)

Water level loss is not the only indicator. These additional symptoms should alert you:

1. Visible cracks in the pool shell. Any crack in the tile, ceramic, or concrete of the pool shell, no matter how small, is a potential leak point. Structural cracks are especially dangerous because they can grow over time.

2. Loose or bulging tiles. When water seeps behind the lining, hydrostatic pressure can detach tiles or create bulges. If you see pieces that “sound hollow” when tapped, there is water behind.

3. Cloudy or hard-to-maintain water. A leaking pool loses not only water but also chemicals (chlorine, pH, algaecide). If you notice that you need to add chlorine more frequently than usual or the water turns green quickly, there may be a leak that constantly dilutes the treatment.

4. Excessive consumption of chemicals. Directly related to the previous point. If you used to spend X kilos of chlorine per month and now you need double, the “new” water you add to compensate for the leak is diluting the treatment.

5. Wet areas or puddles around the pool. If permanently wet areas appear on the grass, embankment, or slab around the pool — especially if they are in the direction of the suction or return pipes — there is probably a leak in the buried hydraulic installation.

6. Ground subsidence. In severe cases, the leak can erode the ground under the pool or around it, causing subsidence, cracks in the pool beach, or unevenness in the adjacent grass.

7. Air bubbles in the returns. If you see air bubbles coming out of the return nozzles when the filter is running, it may indicate that there is an air intake in the suction pipe, often associated with a crack or faulty joint.

When the bucket test is NOT enough

The bucket test is an excellent first diagnostic tool, but it has important limitations you should be aware of:

Does not detect leaks in the pipe circuit

The bucket test only measures water loss in the pool shell. If the leak is in a buried pipe (suction, return, bottom drain), the pool may lose water only when the filter is running, giving inconsistent results.

Complementary test: Perform the bucket test twice: once with the filter running and once with the filter off. If the pool loses more water with the filter running, the leak is probably in the pipe circuit.

Does not locate the leak point

Even if the test confirms that there is a leak, it does not tell you where it is. A pool can have multiple leaks simultaneously: one in the shell, another in the skimmer pipe, and another in a fitting. Only professional detection can locate each point.

Does not work with intermittent leaks

Some leaks activate only under certain conditions (pressure, temperature, water level). A crack in the waterline may stop leaking when the level drops below it, causing the bucket test to give false negatives.

Unpredictable weather conditions

If the wind changes during the 24 hours of the test, or there are partial clouds, the evaporation of the bucket and the pool may vary unevenly, giving unreliable results.

How Telefuga detects leaks in pools: the professional process

When the bucket test confirms (or strongly suggests) a leak, the next step is professional detection. At Telefuga, our process for pools is the most comprehensive in the sector in the Levante area:

Phase 1: Pressure test of the circuit (30 minutes)

Before getting into the water, we check the tightness of the entire hydraulic circuit. We individually pressurize each pipe (suction, return, bottom drain, cleaner) and observe if it maintains pressure. If a pipe loses pressure, the leak is in the buried circuit.

Phase 2: Tracer gas (helium/hydrogen) (45-60 minutes)

We inject tracer gas (helium or hydrogen at 5%) into the suspected pipe. The gas escapes through the crack, rises through the ground, and emerges at the surface, where we detect it with a high-sensitivity sensor. This technique is especially precise for buried pipes at a depth of 40-80 cm, which is the usual depth in pools.

Phase 3: Inspection with professional diver (60-90 minutes)

Our professional diver inspects the inside of the pool shell meter by meter, looking for cracks, faulty joints, loose pieces, and any point of loss. They use specialized equipment:

• Indicator dye: Applies biodegradable dye near suspected points. If there is a leak, the dye is visibly “sucked” towards the crack
• Underwater camera: Records in high definition to document findings
• Hydrophone: Detects the sound of water filtering through cracks that are impossible to see with the naked eye

Phase 4: Inspection with CCTV camera (30-45 minutes)

We introduce an articulated CCTV camera through the inside of the pipes to visually inspect their condition: cracks, roots, displaced joints, crushes, or obstructions. This inspection is crucial in pools older than 15-20 years where PVC pipes may have degraded.

Phase 5: Report and repair budget (same day)

We provide a detailed report with the exact location of each leak found, photographs, videos, and a fixed budget for the repair.

Prices for leak detection and repair in pools

Prices vary depending on the size of the pool, the complexity of the installation, and accessibility. Request a personalized quote for your specific case.

Advanced bucket test: the variant with filter

For more information, we recommend doing two consecutive bucket tests:

Test A (24h with filter on): Perform the standard test with the filtration pump running in its normal cycle. Note the difference between the bucket and the pool.

Test B (24h with filter off): Repeat the test with the filter completely off. Note the difference.

This information is very valuable for the detection professional because it allows them to orient the search from the very beginning, reducing the time and cost of the inspection.

The real cost of ignoring a leak in the pool

Many owners opt for “just filling it up” because they perceive detection as an unnecessary expense. Let’s look at the real numbers:

Comparing with the cost of detection (from €150), the amortization is evident even for small leaks. Moreover, an unrepaired leak always worsens over time: water erosion progressively enlarges the crack.

Preventive maintenance to avoid leaks in pools

• Annual inspection of joints and seals: Visually inspect all joints of the tile, skimmers, returns, and drains before each bathing season
• pH control: An out-of-range pH (below 7.0 or above 7.8) accelerates the degradation of joints, mortar, and pipes
• Proper winterization: Do not empty the pool in winter — the pressure of the water keeps the shell stable. Emptying can cause the shell to lift due to hydrostatic pressure from the ground
• Circuit inspection every 3-5 years: Especially in pools older than 10 years, a preventive pressure test can detect weaknesses before they become leaks
• Protect pipes from roots: Trees near the pool can introduce roots into the joints of the pipes. Maintain a perimeter free of vegetation of at least 2 meters

Conclusion

The bucket test is the smart first step when you suspect your pool is losing water. It is free, simple, and, if well executed, quite reliable. But if the test confirms a loss greater than the normal evaporation for your area, do not try to guess where the leak is: every day that passes you lose water, chemicals, and money, and the leak will only worsen.

Telefuga has been repairing pools in southeastern Spain for 16 years, with 8,050 pools attended and a rating of 4.8/5 on Google (319 reviews). Our team of professional divers, tracer gas, and CCTV camera locates the exact leak without emptying the pool in most cases.

Request your pool diagnosis from €150 → Service available in Murcia, Alicante, Valencia, Albacete, and Almería. Also check our pages on leak detection in pools and pool repair.