Swimming Pool Problems in Spain — What Can Go Wrong and Why

Having a pool in Spain is wonderful. Maintaining one is another matter entirely. Beyond the routine cleaning and chemical balancing that any pool needs, there are a handful of more serious problems we get called in to fix on a regular basis. Here’s what to watch out for, and what’s usually behind it.

The pool is losing water

This is the most common complaint we hear. The water level keeps dropping, and it’s not just evaporation.

There are two main causes: a problem in the pipework, or a crack in the shell of the pool itself.

Pipework leaks

The plumbing system of a pool runs under pressure, and if there’s a crack, a bad joint, or a poorly fitted connection somewhere, water will find its way out.

The first step is a pressure test — we seal the system and pump it up to pressure, then watch whether the pressure holds over time. If it drops, there’s a leak somewhere. Locating it is the next challenge. If the problem is in the pump room or somewhere accessible, it’s usually straightforward to find and fix. If it’s underground or under the terrace, we use a camera probe — a small device fed through the pipe — to find where the issue is.

Why does this happen in the first place? Usually it comes down to corners cut during construction. Pool plumbing needs to be done with pipes rated for pressure and for contact with pool chemicals — the chlorine and other treatments used to keep the water clean are quite aggressive, and standard drainage pipe simply won’t hold up. We’ve seen pools plumbed with ordinary sewer pipe. It works for a while, then it doesn’t.

Joining pipes properly also matters more than it sounds. PVC pipe is glued together, and that glue needs to be applied correctly — evenly, on both surfaces — and left to cure before the system is pressurised. When builders are in a hurry, they skip the curing time and put water through a fresh joint. Over time, those joints fail.

The cost of fixing a pipework leak depends entirely on where it is. If it’s accessible, it’s a manageable job. If it’s under tiles or under concrete, you’re looking at more work — and more cost.

Cracks in the shell

If the pool itself has cracked, you’ll typically need to drain it, remove the tiles in the affected area, and get down to the concrete to assess the damage.

When we find a crack, we open it up — cut it wider and deeper — to see the condition of the reinforcing steel inside. If the rebar has corroded, we deal with that first. Then the crack is filled with appropriate concrete, allowed to cure, waterproofed, and retiled.

This is labour-intensive work, which makes it expensive. But it’s necessary, because a crack that’s just patched at the surface will open up again.

Why do pool shells crack? Sometimes it’s soil movement — the ground shifts slightly, the pool moves with it, and something gives. Sometimes it’s poor construction. A properly built pool shell is sprayed under pressure with structural concrete, reinforced with a properly tied steel mesh. This isn’t the same concrete you’d use for a garden wall, and the reinforcement isn’t optional decoration. When builders use inferior materials or skip the reinforcement, the shell is vulnerable.

One case that stays with us: a client bought a house and called us because their pool was losing water fast. When we drained it and lifted a few tiles, we discovered the shell wasn’t concrete at all. It was brick. Someone, at some point, had built a brick-lined pool and tiled over it. How anyone swam in it, or whether they did at all, remains a mystery to us. But it does illustrate that with pools, you genuinely never know what you’re inheriting when you buy a property.

Waterproofing — the step that’s too often skipped

Whether we’re doing a full pool renovation or just replacing tiles, we always apply a proper waterproofing membrane before the tiles go on. It’s a two-component product applied over a reinforcing mesh that covers the entire inner surface of the pool.

Think of it like a flexible rubber lining inside the concrete shell. Even if the shell moves slightly — which over time, most do to some degree — the membrane has enough flexibility to keep water where it belongs. Concrete alone, even good concrete, is porous. Waterproofing is what actually keeps the water in.

Skipping this step is another way builders save money at your expense.

Green water and grout that won’t come clean

Algae, green tinting, and general discolouration of the water are usually a maintenance issue rather than a structural one — a job for your pool cleaning company rather than a builder.

But if the grout between the tiles has absorbed algae, mould, or mineral deposits, cleaning the water won’t help. The contamination is inside the grout itself. The only real fix is to remove the old grout and regrout properly.

In some areas, the local water is quite aggressive — high mineral content, particular chemical composition — and it attacks standard grout over time no matter how well it was applied. In these cases, the best solution is epoxy grout. It’s significantly harder than standard grout — closer to glass in terms of density — and it doesn’t absorb anything. Algae and deposits stay on the surface and can be cleaned off.

Epoxy grout costs more, both in materials and in labour — it requires skill to apply correctly and doesn’t forgive mistakes. But in the right circumstances, it’s the only option that actually solves the problem rather than just delaying it.

The short version

Most serious pool problems come down to one of two things: bad workmanship during construction, or materials that weren’t right for the job. Proper concrete with proper reinforcement, correct pressure-rated pipework, well-made joints, and a waterproofing membrane underneath the tiles — these aren’t luxuries. They’re what makes a pool last.

If your pool is losing water, don’t ignore it. The longer a leak runs, the more damage accumulates — to the pool itself, to the surrounding terrace, and potentially to the structure of the house. Get it looked at.

The calculator gives you a rough starting point — though pools vary enough that a proper quote always needs a site visit. If you’d like to talk it through, get in touch.