Anyone with a private pool knows the feeling: you glance at the waterline and wonder, “Was it this low yesterday?” A bit of water loss is completely normal, but at what point should you start to suspect something else? Whether you look after your own pool or rely on property management, understanding how and why water disappears is at the heart of proper swimming pool maintenance.
Normal water loss — The role of evaporation
A healthy pool always loses some water through evaporation. Heat, wind and sunlight all play their part. During warmer weeks, a typical pool on the Costa Brava might lose two to four millimetres of water per day. That adds up to about one to two centimetres each week — around five to eight hundred litres for an average family pool. It may sound like a lot, but it’s simply part of the climate.
The rate depends on how exposed your pool is to wind and sun, whether you use a cover, and how often people are swimming. When the air is hot and dry, the surface water evaporates more quickly. If you have a fountain or waterfall feature, expect even higher evaporation — moving water loses moisture faster. Many owners find that topping up once a week keeps the level stable throughout the season.
What’s important is consistency. If you start to notice that the waterline drops unusually fast, even on cooler or cloudy days, or if you have to refill every few days, it’s time to consider another explanation.
When a leak might be the problem
Not all water loss comes from evaporation. Leaks are far more common than most people realize, especially in older pools or ones that have gone through hot summers and mild ground movement. The usual suspect is the skimmer — where plastic meets concrete, small cracks often develop that allow water to escape quietly over time. Another common area is around the underwater lights. The cable gasket hardens with age, leaving tiny gaps where water seeps out.
Pipes can also be the cause. Underground suction or return lines can shift or crack, especially if the surrounding soil dries and moves. And even a hairline fracture in the pool’s structure can be enough to lose a few hundred litres a week. These leaks are often invisible — you won’t see puddles, just a slow, persistent drop.
One simple way to check is the bucket test. Fill a bucket with pool water, place it on a step, and mark both levels. After 24 hours, compare them. If the pool level has fallen more than the bucket’s, you’re likely losing water through a leak rather than evaporation.
Why balance matters
Water loss is more than a nuisance — it affects everything else in your pool. When levels drop too low, the pump may start to draw air, which can damage seals and shorten its lifespan. Constant refilling also changes the chemistry of the water. Every time you add fresh water, you dilute chlorine, stabilizers and minerals, forcing the system to rebalance. Over time, this increases chemical use and wear on materials.
Consistent swimming pool maintenance prevents most of these problems. Regular checks of water levels, filtration pressure and return flow can reveal small issues early. For second-home owners, this is often handled through property management services, which ensure someone is always keeping an eye on the details while you’re away.
Owning a pool should be about enjoyment, not stress. Once you understand your pool’s natural rhythm — how much water it loses, when to top it up, and what signs to watch for — you’ll know exactly when something’s wrong. A well-maintained pool isn’t just cleaner; it lasts longer, costs less to run, and keeps every sunny day on the Costa Brava as relaxing as it should be.