Pool Water Loss Calculator
Get a quoteIs your pool leaking, or just evaporating?
See if your pool’s water loss is normal, and what any extra costs you each month.
1 · Your pool
Measure the water surface, length and width in metres. Odd shape? Tick Freeform and enter the area.
2 · Conditions
Water + sewerage, City of Cape Town 2026/27, about 30 kl/month household (incl VAT). Elsewhere? Enter your own rate.
3 · How much water are you losing?
Tip: 1 cm = 10 mm.
How to do the bucket testClose
Use this test to determine if water loss is due to evaporation or a leak.
- Place the bucket on the first or second step of the pool, ensuring it is stable.
- Fill the bucket with pool water up to about 7 cm from the top.
- Record the water levels inside and outside the bucket.
- Turn off the filtration system and any timers.
- Wait 24 to 48 hours, then check and record the new water levels.
- Same drop inside and outside? Likely evaporation.
- Pool level drops more than inside the bucket? Possible leak.
Additional testing: repeat the test with the filtration system on. If water loss increases, the leak may be on the jet lines. If the loss remains consistent, the issue is likely on the suction line or the pool structure.
Record your readings
Note the levels at the same time each day. A difference that keeps growing points to a leak; send us a photo of your readings on WhatsApp 079 540 1802 and we will interpret them for you.
| Day | Date and time | Pump on / off | Bucket level (mm) | Pool level (mm) | Difference (mm) |
|---|---|---|---|---|---|
| Start | |||||
| Day 1 | |||||
| Day 2 | |||||
| Day 3 | |||||
| Day 4 |
Measure from the rim of the bucket to the water inside, and from the top of the step or a marked tile to the pool water. Do not top up the pool while the test runs; if it rains, start again.
Enter your pool details above
Your result appears here as you type.
Guideline estimate, not a diagnosis. Only a professional leak detection inspection can confirm and locate a leak.
How we worked it out
Not sure what your result means? Call or WhatsApp us for advice over the phone.
Normal evaporation
–
estimate from the weather
Your actual loss
–
Extra loss
–
above normal evaporation
Share of your pool lost each day
Extra lossPool water
Enter your pool size to see this.
Sinking feeling? Let’s get to the bottom of it.
A bucket-test difference of more than a few millimetres a day is worth checking. Our technicians test your pool’s plumbing and fittings to find where the water is going.
Prefer to talk? Call 079 540 1802 or 021 200 5887, or WhatsApp us.
Book a leak detection inspection
- We contact you to discuss your situation and book a leak detection inspection if needed.
- A technician tests your pool’s plumbing and fittings by process of elimination. The standard visit covers the first 90 minutes on site.
- You get a report of the tests and findings, with a quotation if a repair is needed.
Dry run: nothing was sent. This is what the website form (Gravity Forms form 3) would receive:
3-year workmanship guarantee
On the repairs we carry out, as set out in our repair terms.
Some of the equipment our technicians use
Keep a copy for yourself Your pool water loss result
Your summary is ready once you’ve entered your pool size and how much water you’re losing.
In the print window, choose Save as PDF as the printer.
Your copy is ready
Leave your details to get your copy.
Dry run: nothing was sent. This is what Gravity Forms form 5 would receive:
Questions pool owners ask
Every pool loses some water to evaporation; a leak is loss on top of that. The simplest home check is the bucket test: a bucket of pool water on the step loses only to evaporation, so if the pool drops more than the bucket over 24 to 48 hours, you may have a leak. This calculator does the comparison with your area’s live weather.
Is my pool leaking or just evaporating?
Every pool loses water to evaporation, depending on the season, the wind and whether the pool is covered. In the Cape Town area that came to about 1.7 mm a day in June and July and 6.3 to 7.7 mm a day in December over the last 12 months (see the table below). If your pool drops more than about 2 mm a day above that, it’s worth booking a leak detection inspection. The bucket test is the reliable way to tell them apart, because the bucket experiences the same weather as the pool but cannot leak.
How much water should a pool lose to evaporation per day?
It depends on the weather. Over the last 12 months our calculation gives about 1.7 mm a day in June and July and 6.3 to 7.7 mm a day in December for Brackenfell, Constantia and Paarl. On a 10 m by 5 m pool (50 square metres) that is about 85 litres a day in winter and 315 to 385 litres a day at the summer peak. Wind, shade and swimming change it from day to day, which is why this calculator uses your area’s live weather.
How much does a pool leak cost per month?
It depends on the size of the leak and your municipal tariff. At the City of Cape Town 2026/27 rate of about R78 per kilolitre for water and sewerage (incl VAT, for a household using about 30 kl a month), a leak losing 200 litres a day costs roughly R470 a month, before any damage to surrounding structures. Other municipalities charge different rates.
How reliable is this calculator?
It is a guideline estimate, not a diagnosis. Evaporation varies with weather, wind and pool use, and splash-out from swimming can look like a small leak. The only way to confirm and locate a leak is a professional leak detection inspection.
Typical pool evaporation by month in the Cape Town area
| Month | Brackenfell | Constantia | Paarl |
|---|---|---|---|
| January | 6.9 | 6.2 | 7.4 |
| February | 5.7 | 5.0 | 6.0 |
| March | 5.2 | 4.6 | 5.3 |
| April | 2.9 | 2.9 | 3.0 |
| May | 1.8 | 1.8 | 1.8 |
| June | 1.7 | 1.7 | 1.7 |
| July | 1.8 | 1.7 | 1.8 |
| August | 2.6 | 2.5 | 2.6 |
| September | 3.8 | 3.6 | 3.9 |
| October | 4.9 | 4.4 | 5.1 |
| November | 7.1 | 6.1 | 7.5 |
| December | 7.2 | 6.3 | 7.7 |
Source: Open-Meteo historical weather data, FAO reference evapotranspiration × 1.1, our calculation, 01 Oct 2025 to 30 Sep 2026. Weather data by Open-Meteo.com (CC BY 4.0).
Last updated 21 Oct 2026 · Water price: City of Cape Town 2026/27 · Evaporation: Open-Meteo weather data, our calculation
Not sure what your result means? Call or WhatsApp us for advice over the phone.