Pool water treatment on the Costa Blanca

Treatment systems and when to use each

There are four main water-treatment systems used today in Costa Blanca pools. Each has advantages, drawbacks and specific use cases.

Traditional chlorine, tablets, granular or liquid, is still the most used for proven effectiveness and reasonable cost. Main drawback: it requires continuous top-up because chlorine gets consumed disinfecting and evaporates under UV. A traditional chlorine pool needs 200-500 g per week in high season depending on volume and sun exposure. The pool smells of chlorine, irritates eyes more and leaves skin slightly dry after long swims. Still valid and economical, but no longer the best option when budget allows alternatives.

Salt chlorination is the current trend on the Costa Blanca. Common salt is added to the water (4-6 kg per cubic metre) and an electrolyser installed in the filtration loop converts the salt to chlorine continuously and automatically. Benefits: much softer water on skin and eyes, no chemical chlorine smell, no manual chlorine to add weekly, more stable chemistry because generation is continuous. Single drawback: initial investment in the electrolyser (1,100-1,700 euros installed for standard pools), paid back in 3-4 years through chlorine savings and bathing quality improvement.

Bromine is the alternative to chlorine for people allergic or with very sensitive skin. Works similar but bromine doesn’t evaporate under UV like chlorine and doesn’t generate the typical smell. More expensive to maintain and requires automatic dosing pumps, making it less common in small residential pools and more used in spas and indoor pools.

Active oxygen (hydrogen peroxide) is the eco option for clients refusing chlorine entirely. More expensive and requires more frequent analysis and replenishment than any alternative, so almost nobody chooses it for residential use. Its niche is small private spas where water is renewed often.

Parameter balancing: the detail that matters

The chosen disinfectant is just one of several parameters that must be kept in correct ranges for the pool to work well. pH (7.2-7.6) directly affects chlorine effectiveness: deviated pH and chlorine loses efficacy exponentially, with algae appearing despite apparently correct chlorination. Total alkalinity (80-120 ppm) buffers the pH and prevents abrupt changes. Calcium hardness (under 250 ppm) determines how much lime scales in filters, walls and waterline. Stabiliser (cyanuric acid 30-50 ppm) protects chlorine from UV degradation.

When even one of these parameters drifts significantly, the whole system starts to fail and typical problems appear: cloudy water that won’t clear, green or black algae despite chlorinating, visible lime scaling on the waterline, eye irritation even with low chlorine. Diagnosing and correcting the imbalance requires precise analysis and knowledge of water chemistry, what we do at each maintenance visit.