Pool leak or evaporation? Measure the drop and read the result before calling a technician
You fill the pool, and a few days later the water has dropped below the skimmer opening. Is it the Riyadh sun taking its daily share, or is water escaping through a wall or a buried line? The question of pool leak or evaporation comes up every summer, and leaving it unanswered can mean a higher bill and saturated soil under the surrounding paving.
In this guide you measure the drop correctly and compare it with the estimated evaporation range in the Riyadh Pool Safety Index. Then you run the bucket test, which separates the effect of the weather from real water loss. You will also learn where pools usually leak, and when you need an equipment-based inspection.
What is the pool leak or evaporation tool, and what does it do?
The Riyadh Pool Safety Index is a simple estimating calculator. You enter how much the water level dropped in 24 hours, in cm, and it compares that with fixed limits based on estimated evaporation from uncovered pools in a Riyadh summer: about 0.5 to 1 cm a day. It then gives one of three results: within normal evaporation, slightly higher and worth checking, or clearly high with a leak likely.
This guide covers what the tool does not: how to measure precisely, the bucket test, the usual leak points, and what the lost water costs you. The tool works anywhere, but its limits are set for Riyadh's hot, dry summer.
Who is this tool for?
- Owners of villas and rest houses with an outdoor pool.
- Anyone who maintains their own pool, or supervises a pool maintenance worker.
- Buyers of a villa with a pool who want to check its condition. For the whole villa, see the pre-purchase villa inspection guide.
- Managers of residential compounds with shared pools.
When should you use it?
- When you have to add more water than usual, or the auto-fill runs constantly.
- When your summer water bill rises more than you expect.
- After a repair or renovation, to confirm the loss is back to normal.
- At the start of summer, as a baseline to compare against later.
Where do you use it?
You measure at the pool itself, with the tool on your phone. Put a mark at the skimmer opening or on a fixed wall tile, and measure at the same point every time.
The tool's limits are based on a Riyadh summer. If your pool is in a humid coastal city such as Jeddah or Dammam, or anywhere cooler or more humid, or you measure in winter, normal evaporation is usually lower. The same drop is then more suspicious.
What do you need before you start?
- A ruler or tape measure marked in cm, and tape or a waterproof marker for marking.
- 24 hours with no swimming and no water added, with the auto-fill switched off if you have one.
- No filter backwash during the measurement, because it takes water out of the pool.
- For the bucket test: a clean plastic bucket, and stones or weights to hold it on the step.
How to use it correctly, step by step
Riyadh Pool Safety Index
The tool has a single field: "Pool level drop in 24 hours (cm)". It then applies three fixed limits:
- Up to 1 cm: "Within normal evaporation limits".
- Over 1 and up to 2 cm: "Slightly higher than normal — worth checking".
- Over 2 cm: "Clearly high — a real leak is likely".
The limits do not change with temperature, wind, a pool cover or your city, and the tool says so plainly. Its limits assume an uncovered pool in a Riyadh summer with normal wind. In winter, spring and autumn evaporation is usually lower, so the same drop points more strongly to a leak. A cover greatly reduces evaporation, while strong wind, waterfalls and fountains increase it. It also notes that the reference figure (0.5 to 1 cm a day) is a general guideline, not an official measurement for your location.
Ask about your pool: after the calculation, a section called "Ask about your pool or attach a photo" gives advice consistent with the result and the drop you entered. This section only appears when AI analysis is switched on for the site. If it is unavailable or reaches its limit, the tool keeps working on its fixed rules, with a small note.
Steps for correct use
- Prepare the pool
Fill the pool to its usual level, switch off the auto-fill, and do not backwash the filter. Choose a day when nobody uses the pool, ideally without strong wind.
- Mark the level
Put a strip of tape at the skimmer opening or on a wall tile, and draw a line exactly at the water surface. Note the time.
- Measure after 24 hours
At the same time the next day, measure with the ruler the distance between the line and the new water surface in cm, such as 1.5 cm. Measuring at the same hour reduces the effect of day-night differences.
- Enter the number and calculate
Open the tool, enter the drop in "Pool level drop in 24 hours (cm)", such as 1.5, then tap "Calculate" or press Enter.
- Repeat the measurement
Measure on two or three days in a row and take the average. A single hot or windy day can give a higher figure than usual.
- Ask the AI (optional)
Describe what you notice (such as the drop changing when the pump runs) or attach a photo in the AI section, then tap "Ask".
How to read the result
- "Within normal evaporation limits" (up to 1 cm): nothing to worry about right now in summer. The tool suggests measuring again in a few days. If you measured in winter or in a humid city, even 1 cm may be more than expected, so measure for a full week.
- "Slightly higher than normal — worth checking" (over 1 and up to 2 cm): run the bucket test explained in the next section; it settles the question.
- "Clearly high — a real leak is likely" (over 2 cm): the loss clearly exceeds normal evaporation. The tool suggests an electronic inspection to find the source, whether the pool floor, the filter line or the pump. The bucket test is still useful to see whether the loss is linked to the pump running.
If nothing appears after you tap the button, check that you entered a valid number, not a negative one. The tool shows no result for an empty field.
- AI reply: steps and warnings consistent with the calculation result. It does not replace the bucket test or an on-site inspection.
The bucket test, step by step
The bucket test puts water under the same weather conditions as the pool, but with no chance of leaking. The difference between the two is the real loss.
- Fill the pool to its usual level and switch off the auto-fill.
- Place the bucket on the first or second step inside the pool, and weigh its bottom down with stones or weights.
- Fill the bucket with pool water until the level inside matches the pool level outside.
- Mark the water level inside the bucket, and the pool level on the outside of the bucket.
- Run the pump as usual and leave it for 24 hours with no swimming.
- Compare: if the pool dropped clearly more than the bucket, there is a loss other than evaporation.
Repeat with the pump off
Repeat the test for another 24 hours with the pump switched off. If the loss is greater while the pump runs, the source may be in the return lines or the equipment. If it is the same both ways, it may be in the pool shell or a fitting set into it. This is a guide that helps the technician; it does not pinpoint the location.
What controls the rate of evaporation?
Evaporation happens at the water surface, and four factors increase it:
- Heat and sunlight: in direct summer sun, evaporation rises clearly.
- Wind: moving air carries the vapor away, so more water evaporates.
- Dry air: the dry air of Riyadh and Qassim draws more moisture than the humid air of Jeddah.
- Water-to-air temperature difference: a pool heated at night in winter loses more water than you might expect.
There is also normal loss that is not evaporation: splashing, water carried out on bodies, filter backwashing, and fountains and waterfalls. On the other hand, a pool cover reduces evaporation noticeably. So always compare under similar conditions.
Where do pools usually leak, and what are the signs?
The most common places for water loss in pools:
- The skimmer joint with the pool shell.
- The return inlets and their lines buried under the deck.
- The main drain in the floor.
- The light niche and its cable conduit.
- Cracks in the shell or in the tile joints.
- The equipment room: the pump seal, the filter, the valves and the backwash line.
Helpful signs:
- Wet soil or unusually green grass near the pool.
- Deck tiles sinking or cracking.
- Air bubbles in the returns, or an auto-fill that never stops.
- Algae that keeps coming back despite balanced chemicals, because fresh water is constantly added.
- Water in the equipment room.
Example: how much water is lost?
Take a pool with a surface of 8 × 4 m, or 32 m². Each 1 cm of drop equals 320 liters.
- If the drop is 2.5 cm a day and expected evaporation is about 1 cm, the extra loss is 1.5 cm.
- 1.5 cm × 320 liters = about 480 liters a day.
- Over 30 days ≈ 14.4 m³ of water, on top of your normal use.
Because Saudi residential water tariffs (NWC) rise in tiers, you may pay a higher rate for this amount, since it sits on top of the household's consumption. To estimate the cost on your bill, see the leak water waste guide.
Common mistakes that spoil the result
- Measuring after a day of swimming or a party. Splashing and water carried out by swimmers add whole cm to the drop.
- Leaving the auto-fill on. It replaces the loss and hides it.
- Backwashing the filter during the measurement.
- Measuring at different points or times. Ripples and wind change the reading.
- Relying on a single day. Take the average of several days.
- Draining the pool to look for the leak. It can be dangerous for the pool shell if groundwater is high, and it removes the reference level the technician needs for testing.
Honest limits of the tool
- The three limits are fixed and based on an estimate for a Riyadh summer. They take no account of the month, the city, wind, a cover or heating.
- The result depends entirely on the accuracy of your measurement. An error of 0.5 cm can move you from one category to another.
- A "normal" drop does not rule out a small leak, especially in winter or in humid weather.
- The tool does not find where the leak is. That needs an equipment-based inspection.
- If floors are sinking or walls cracking near the pool, the structural assessment needs a licensed engineer.
When do you need a leak detection technician?
Ask for a professional inspection if:
- The drop is more than 2 cm a day, repeatedly.
- The bucket test showed a clear difference between the pool and the bucket.
- The soil is wet or tiles are sinking around the pool.
- There is water in the equipment room, or the auto-fill never stops.
- The pool lights or equipment are near a wet area. Switch off the power at the breaker first and do not touch wet equipment. In an emergency in Saudi Arabia call 998 (civil defense) or 933 (electricity); elsewhere, local emergency services.
At Kashf we locate water loss in the pool wall, floor or lines using electronic equipment and pressure testing as the case requires, without random demolition. We then present the right repair and waterproofing and their price before starting, and you receive a written report you can verify. For the price range see the leak detection cost guide, and book from the order page or on WhatsApp at 0544027180. On-site service is available in Saudi Arabia only.
Frequently asked questions
How do I know if it's a pool leak or evaporation?
Measure the drop over 24 hours with no swimming or refilling, then compare it with expected evaporation. In a Riyadh summer that is roughly 0.5 to 1 cm a day. If you see more, run the bucket test: if the pool drops clearly more than the bucket, a leak is likely.
How much does a pool lose to evaporation per day in summer?
For uncovered pools in a Riyadh summer it is usually about 0.5 to 1 cm a day. It rises with heat, wind and dry air, and falls with a cover and humidity. This is a general guideline, and your pool may differ a little depending on its location and shade.
Is the bucket test accurate?
It is one of the simplest and most useful home methods, because the bucket and the pool face the same weather. But its accuracy depends on securing the bucket, matching the two levels at the start, and no swimming during the test. It confirms a loss but does not locate it.
Why does the pool lose more water when the pump is running?
Because part of the system is only under pressure while the pump runs, such as the return lines, inlets and some equipment joints. If the leak is there, the loss increases while the pump runs. This observation helps the technician decide where to start the inspection.
Does a pool cover really reduce evaporation?
Yes. A cover reduces evaporation noticeably because it shields the water surface from sun and wind. So if you measure once with a cover and once without, the comparison is not fair. Keep the conditions the same before judging whether there is a leak.
Can a pool leak through the tiles?
The tiles themselves do not hold the water; the pool shell and the waterproofing beneath them do. But cracked joints or falling tiles may point to movement or damage in the layers underneath. Any crack that keeps coming back is worth inspecting.
Should I drain the pool to find the leak?
It is not advisable before consulting a specialist. Draining can damage the pool shell if groundwater is high, and it takes away the water level the technician needs for testing. Keep the pool full and ask for an inspection first.
How much water is lost if the pool drops 2 cm a day?
It depends on the surface area. In an 8 × 4 meter pool, each 1 cm is about 320 liters. If it drops 2 cm a day and evaporation is about 1 cm, the extra loss is 1 cm, or about 9.6 m³ a month added to your bill.
Can I use the index for a pool in Jeddah or Dammam?
You can, but remember its limits are based on Riyadh's dry summer. Coastal humidity usually lowers evaporation, so the same drop is more suspicious. Rely more on the bucket test, because it measures your own pool's conditions.
Related services
On-site inspections are available in Saudi Arabia; the tools and guides work anywhere.
This guide is educational. It explains estimation tools that help you understand a situation and decide what to do next; confirming a leak and pinpointing it always requires an on-site inspection with instruments. Structural questions are for a licensed engineer to decide.