Why Is My Pool Losing Water? Evaporation vs Leak
Normal Pretoria pools lose 3–7 mm a day to evaporation. Here's the bucket test, the science of surface loss, and when to stop topping up and start investigating.
Every pool loses some water every day. That's normal. But when the level drops faster than it should — or keeps dropping no matter how much you top it up — you may have a leak. The challenge is that evaporation and leaks can look identical from the surface, and mistaking one for the other can cost you thousands in wasted water and rising municipal bills.
This guide will help you understand the difference, run a simple home test, and know when it's time to call a pool leak detection specialist in Pretoria.
How Much Water Should a Pool Lose?
In Gauteng's hot, dry climate, a pool can lose between 3mm and 7mm of water per day through evaporation alone — more during a heat wave or on a windy day. Over a week, that's up to 5cm of water loss, which is roughly 2,000 to 5,000 litres depending on pool size.
That sounds like a lot, but it's entirely normal. The problem is when you're losing more than that, or when the loss doesn't slow down on cooler, calmer days.
Factors that increase evaporation:
- High temperatures (Pretoria summers regularly hit 35°C+)
- Strong wind across the water surface
- Low humidity
- Large pool surface area
- Lack of a pool cover
The Bucket Test: The Simplest Way to Tell the Difference
Before calling anyone, try the bucket test. It's free, easy, and surprisingly accurate.
What you need: A bucket, a marker or tape, and 24 hours.
How to do it:
- Fill a bucket with pool water and place it on the first or second pool step (so it's partially submerged in the same environment as the pool)
- Mark the water level inside the bucket with a marker or piece of tape
- Mark the pool water level on the wall or step
- Turn off the pool pump and auto-fill if you have one
- Wait 24 hours
- Compare the two water levels
What the results mean:
- If both dropped by the same amount: you're losing water to evaporation — no leak
- If the pool dropped significantly more than the bucket: you very likely have a leak
The bucket sits in the same sun, wind, and temperature as your pool — so it accounts for all natural evaporation. If your pool is losing more, something else is happening.
Common Signs You Have a Pool Leak (Not Just Evaporation)
The bucket test is the most reliable DIY method, but these signs can also point to a leak:
- You're topping up the pool more than twice a week
- Wet or soggy ground around the pool edge, equipment area, or return lines
- Visible cracks in the pool shell, coping, or tiles (though not all leaks are visible)
- Increased chemical usage — leaking water takes your chemicals with it
- The pool pump is constantly running to maintain pressure
- Your water bill has increased without an obvious reason — read more in our guide on high water bills with no visible leak
- Air bubbles coming from the return jets (can indicate a suction-side plumbing leak)
If two or more of these apply to you, the bucket test result almost doesn't matter — you likely have a leak.
Where Do Pool Leaks Come From?
Pool leaks can originate in several places, and the location affects how urgently you need to act and how it's detected.
Shell or Surface Leaks
Cracks in the pool shell, typically around fittings, lights, steps, or at the waterline. These are sometimes visible but often hairline cracks that are impossible to see with the naked eye.
Plumbing Leaks
Underground pipes connecting your pump, filter, and returns are a common source. These are completely invisible from above ground and can only be found with specialist equipment — pressure testing, tracer gas, or acoustic listening.
Equipment Leaks
Around the pump, filter, valves, or backwash system. These are usually easier to spot because the equipment is accessible.
Fittings and Penetrations
Around light fixtures, skimmer boxes, return jets, and main drains. These are high-wear areas where sealants deteriorate over time.
Important: Underground plumbing leaks are one of the most common pool leak types in Pretoria and Centurion — and also one of the hardest to find without professional equipment. Read our full guide on underground pipe leak detection in Pretoria.
How We Detect Pool Leaks: No Draining, No Digging
At Source Leak Detection, we use non-invasive methods to find exactly where your pool is losing water — without draining the pool, breaking tiles, or digging up paving.
Our methods include:
- Dye testing — injecting tracer dye near fittings and cracks to see where water escapes
- Pressure testing — isolating plumbing lines to test for pressure drops
- Electronic leak detection — specialist listening devices for underground pipes
- Visual inspection of fittings, shell, and equipment
Most pool leak detection jobs in Pretoria and Centurion take 2–4 hours and cost between R800 and R2,500, depending on pool size and complexity. You get a written report with the exact leak location and recommended repair — which your insurance company (if applicable) will accept.
Note: Pool leaks are usually excluded from standard home insurance. See our guide on what home insurance covers for water leaks in South Africa for details.
What Happens If You Ignore a Pool Leak?
A small leak that loses 5mm of water per day might seem manageable. But over time:
- You'll waste tens of thousands of litres of water per month
- Your water bill will climb significantly
- The surrounding ground becomes saturated, potentially undermining paving, decking, or garden walls
- Chemical imbalances become harder to control
- The pool shell or structural elements can be damaged by sustained water movement
In Pretoria and Centurion, where water restrictions are a real concern, a leaking pool is also a compliance issue during drought periods.
DIY Pool Leak Detection: What You Can Check Yourself
Before calling us, here are a few things you can inspect:
- Check all visible fittings — look for wetness, white mineral deposits, or cracks around the skimmer, return jets, and lights
- Inspect the equipment pad — look for drips, wet soil, or rust stains around the pump, filter, and valves
- Check the backwash line — if it's constantly running water, your multiport valve may be leaking
- Look at the pool floor — cracks are easiest to see when the light is right (morning or evening)
- Run the bucket test as described above
If you find an obvious fitting leak, a qualified pool technician may be able to repair it. But if the bucket test shows significant loss and you can't find a visible cause, you need professional detection equipment.
Frequently Asked Questions
Q: How much does pool leak detection cost in Pretoria? A: Source Leak Detection charges between R800 and R2,500 for pool leak detection, depending on pool size and complexity. You receive a detailed written report with the leak location.
Q: Can a pool leak fix itself? A: No. Leaks don't seal themselves. Algae or debris can temporarily slow a leak, but the underlying fault remains — and usually gets worse.
Q: My pool is losing about 2cm per week. Is that a lot? A: In summer, 3–5mm per day is normal evaporation. 2cm per week (roughly 3mm per day) could be evaporation alone in hot weather. Run the bucket test to check. If it's more than evaporation, book a detection.
Q: Do I need to drain the pool for leak detection? A: Not with our methods. We use non-invasive techniques that work on a full pool. No draining required.
Q: How long does it take to find a pool leak? A: Most jobs take 2–4 hours. We arrive, inspect, test, and provide a written report on the same visit.
Book Your Pool Leak Detection Today
Source Leak Detection has been finding pool leaks in Pretoria, Centurion, and across Gauteng for over 17 years. We use non-invasive methods, arrive the same day, and give you a written report with the exact leak location.
📞 Call us now or request a quote — we'll sort it out without unnecessary digging or disruption.
Related reading: