TL;DR
- A Paarl pool losing a few millimetres a day in summer is almost certainly evaporation. A centimetre or more a day is worth investigating.
- The bucket test settles it in 24 hours, and it costs nothing. Switch the auto-fill off first, or it will hide the answer.
- Where the level stops tells you where the leak is. The skimmer throat is the single most common culprit.
- Worse with the pump on means the return line. Steady whether the pump is on or off means the shell, skimmer or suction side.
- Leaks in buried lines wash soil out from under paving. The repair is cheap; the subsidence afterwards is not.
September is when Paarl pools come back to life. The cover comes off, the pump goes back onto a summer cycle, and within a few weeks you notice you are standing there with a hosepipe more often than you remember from last year. And the question is always the same one: is it leaking, or is that just what a pool does out here?
It is a fair question, because in this valley the honest answer is usually "just what a pool does". Paarl summers are hot, dry and windy, and an open body of water gives up a genuinely surprising amount to the air. But not always. And the difference between the two is worth a day of your attention, because a real leak that gets topped up automatically all summer is both an expensive water bill and, if it is in a buried pipe, a slow washing-away of the ground under your paving.
First, what normal evaporation actually looks like
You cannot judge a leak without knowing what the baseline is, and most people badly underestimate it.
An uncovered pool in a hot, dry Boland summer typically loses a few millimetres of depth every day. That does not sound like much until you do the arithmetic on surface area: on a standard eight-by-four pool, a few millimetres is a few hundred litres. Over a week it is a visible drop down the tile line, and over January and February it is a lot of hosepipe.
Three things push it higher, and Paarl has all three:
- Heat. The obvious one. Warm water and hot dry air move moisture faster.
- Wind. The underrated one. Wind sweeps saturated air off the surface and replaces it with dry air, and a windy site can roughly double the loss of a sheltered one. If your pool sits open to the south-easter, you lose more than your neighbour behind a hedge.
- Low humidity. The dry summer air in the Winelands is thirsty in a way that a humid coastal summer is not.
Add those together and a Paarl pool losing two to three centimetres over a week in midsummer can be perfectly healthy. So the useful rule is not "my pool is dropping, therefore it leaks". It is this:
The rough rule of thumb
Losing a few millimetres a day is weather. Losing a centimetre or more a day, especially if it carries on through cooler, still weather, is worth investigating. Anything that keeps dropping in winter, when evaporation is a fraction of what it is in February, is almost certainly a leak.
The bucket test, step by step
This is the one test worth doing before you call anybody, because it removes the weather from the equation entirely. The logic is simple: a bucket of pool water standing in the pool experiences exactly the same sun, wind and air as the pool does. So evaporation takes the same depth from both. Anything the pool loses over and above the bucket has gone somewhere else.
- Switch off the auto-fill. Do this first. An automatic top-up valve will quietly refill the pool overnight and hide the exact thing you are trying to measure. This single step is why most home tests fail.
- Fill a bucket with pool water and stand it on a step, so the water inside the bucket sits level with the water in the pool. Using pool water rather than tap water matters, it starts at the same temperature.
- Mark both levels. A strip of masking tape or a waterproof marker: one mark inside the bucket, one on the outside for the pool level.
- Leave it 24 hours, running the pump on its normal schedule. Note whether the pump was running or off, you will want that later.
- Compare the two drops. If they match, it is evaporation and your pool is fine. If the pool has dropped noticeably further than the bucket, the gap between them is your leak.
If the answer is ambiguous, run it a second time with the pump switched off for the whole 24 hours. The comparison between those two runs is genuinely diagnostic, and it is the next section.
The auto-fill trap
An auto-fill valve is the reason a lot of pool leaks run for years undetected. The level never visibly drops, so nobody suspects anything, and the leak turns up as a water bill that has crept up and stayed up. If your bill has climbed and you have an auto-fill, test the pool even if the level looks perfect.
Reading where the leak is, for free
Here is the part most people do not know, and it can save you a lot of guesswork. A leak can only drain a pool down to its own level, and then it stops. Water above the hole runs out; water below it has nowhere to go. So if you let a leaking pool find its own level and it settles somewhere and holds, that level is pointing straight at the leak.
What the stopping point usually means:
- It stops just below the skimmer mouth. This is the most common pool leak there is. The skimmer box is plastic set into concrete, the two materials move at different rates, and eventually the throat cracks away from the pool wall right at the waterline. Good news: it is one of the cheaper repairs.
- It stops level with the pool light. The light niche and the conduit running out of the back of it are a classic leak path, and the water often ends up travelling along the conduit rather than straight into the ground.
- It keeps going well below both. Now you are looking lower down: the main drain, a crack in the shell, or a buried suction or return line.
- It only drops while the pump runs. That points at the pressure side, the return line and its fittings, because they are only under pressure when the pump is on. A leak that behaves the same whether the pump is on or off is on the shell, the skimmer or the suction side instead.
- The pump keeps losing prime, or bubbles blow back into the pool. That is the suction line drawing air in through the same fault that lets water out.
Two more things worth walking round and looking for: a patch of lawn beside the pool that stays green and spongy through a dry Paarl February, and paving next to the pool that has started to sink or lift at a corner. Both mean water is going into the ground where it should not be.
Do not let it drain all the way down
Letting a pool find its own level is a useful diagnostic, but do not let it empty. An empty or very low pool can float out of the ground when the water table is high, which is a real risk on the low-lying plots near the Berg River after winter rain. Let it settle, note the level, then stop there.
Why it is usually not the shell
Most people's first thought is a crack in the pool itself, and most of the time they are wrong. In our experience the order of likelihood runs roughly: skimmer box, then the light niche, then the buried suction and return lines, then the main drain, and only then the shell.
The shell does crack, and older marbelite pools in Paarl crack more than most. The reason is the ground. The clay-heavy soils through parts of the valley swell when they take up water through a wet Boland winter and shrink back through the dry summer, and a rigid concrete structure sitting in soil that moves like that gets worked on year after year. That is also why the pipework fails: a buried PVC line takes the same movement, and the fittings are where it gives.
The practical consequence is about your paving. A pool surround is usually the nicest hard landscaping on the property, and the wrong way to find a leak is to start lifting it and looking. Pressure-testing the lines first tells you which line is losing before anything is opened, and acoustic tracing then narrows it to a point you can mark with chalk. That is the difference between lifting one square metre and lifting a courtyard.
What it costs to leave it
It is tempting to keep topping up and deal with it next season. Two reasons not to.
The first is simply the water. A leak losing a centimetre a day off a standard pool is running a meaningful volume of municipal water into the ground every week, and if the auto-fill is doing the topping up you are paying Drakenstein for every litre of it without ever noticing the moment it happens. Over a full Paarl summer that adds up to a number most people are unpleasantly surprised by.
The second is the damage, and it is the expensive one. Water escaping from a buried line under a paved surround does not just disappear, it washes the fines out of the soil supporting that paving. The first sign is usually a slab that has dropped a few millimetres at one corner. By the time it is obvious, you are not fixing a pipe any more, you are relaying a surround. The pipe repair was always going to be the cheap part.
When to stop testing and call someone
Do the bucket test first, always. It is free, it takes a day, and it either puts your mind at rest or gives whoever comes out a genuinely useful head start. Call when:
- The bucket test shows the pool dropping clearly faster than the bucket.
- The level keeps falling in cool, still weather, or through winter.
- You have wet ground, spongy lawn or sinking paving near the pool.
- The pump keeps losing prime or you are getting air back through the returns.
- Your water bill has climbed and stayed there with no change in the household.
When we come out for pool leak detection in Paarl, the first thing we do is confirm the loss is real and not the weather, because there is no sense charging anyone to chase evaporation. Then we isolate and pressure-test the suction and return lines separately to find which one is losing, trace it acoustically to a single marked point, and quote the repair on what is actually there. It is the same approach we use for hidden leaks inside a house on our leak detection page, pointed at a pool instead.
Do the bucket test this week, before the real heat arrives. If it comes back clean, you have lost a day and gained a summer of not wondering. If it does not, you have found it in September rather than in February, which is the cheaper month by a long way.