Pool Water on Mallorca: Salt Chlorination or Chlorine?

Treating pool water on Mallorca is more demanding than in most of northern Europe or North America: the tap water is extremely hard, the water temperature stays above 28 °C (82 °F) for weeks in summer, and the season runs from May to October. If you treat your pool water on Mallorca the wrong way, you will quickly be fighting cloudy or green water and end up paying twice. This post compares salt chlorination, classic chlorine, active oxygen, and UV, lists the right water values, and works out the annual costs. The running pool costs are only one part of the running and operating costs on Mallorca you should budget for as an owner.

Why pool water on Mallorca needs special care

Three factors make water care on the island harder than for a garden pool back home. First, water hardness: Mallorca's drinking water comes mainly from limestone aquifers and from desalination plants. In many municipalities the water comes out of the tap with well over 300 mg of lime (calcium carbonate) per liter, making it some of the hardest in Spain. High lime content pushes the pH up, scales up salt chlorinator cells and heat pumps, and turns the water milky.

Second, the temperature: from about 28 °C water temperature, algae and bacteria multiply much faster, while at the same time chlorine breaks down rapidly under the sun's intense UV radiation. In July and August a pool on Mallorca uses several times the chemicals the same pool would need in a cooler climate.

Third, the season: six months of swimming plus Sahara dust, pollen, and salty air mean the filter system has to run for several hours every day. The post on pool maintenance by a pool company explains how to keep the run times and the equipment under control and what a company charges for it.

Salt chlorination, chlorine, active oxygen, and UV compared

Salt chlorination is a disinfection method in which salt is added to the pool water (about 3 to 5 grams per liter) and an electrolysis cell continuously produces chlorine from it. The water disinfects itself continuously without you having to add chlorine tablets or granules.

For comparison: seawater contains around 35 grams of salt per liter, so a saltwater pool has only about a tenth of that. The water tastes slightly salty but does not sting the eyes.

Method	Advantages	Disadvantages
Salt chlorination	Continuous disinfection, little manual work, pleasant water	Purchase 800 to 2,500 EUR, cell scales up in hard water
Classic chlorine	Cheap, available everywhere, works fast	Regular dosing needed, chlorine smell, over-stabilization possible
Active oxygen	Odorless, gentle on the skin	Hardly reliable above 28 °C water temperature
UV system	Significantly reduces chemical demand	Only in combination with chlorine or salt, no residual effect in the pool

For Mallorca this means in practice: active oxygen on its own is out for most pools, because it is too weak at summer water temperatures. UV systems are a sensible addition but do not replace a disinfectant in the pool. In practice the choice comes down to classic chlorine versus salt chlorination, and if you do not want to dose by hand every week, you are better off with the chlorinator. Important with hard island water: choose a cell with automatic polarity reversal and still check it for lime deposits once or twice a season.

The right water values: pH, free chlorine, and cyanuric acid

Without stable values, the best method is useless. These target values have proven themselves for private pools on Mallorca:

• pH: 7.0 to 7.4. Because of the hard water, the pH on Mallorca almost always drifts upward. pH minus is therefore part of the basic kit, and with salt chlorination the pH rises additionally by design.
• Free chlorine: 0.5 to 1.5 mg/l. In high summer, keep it toward the upper end.
• Cyanuric acid (stabilizer): below 50 mg/l. If you use stabilized chlorine tablets for months, cyanuric acid builds up. From about 100 mg/l the chlorine barely works anymore, and only a partial water change helps.
• Alkalinity (TA): 80 to 120 mg/l. It buffers the pH and prevents constant swings.

As an official reference, it is worth looking at the Spanish Real Decreto 742/2013: it prescribes a pH between 7.2 and 8.0 and free chlorine between 0.5 and 2.0 mg/l for public and community pools in Spain. The standard is not binding for private single-family pools, but it is the benchmark that pool companies on Mallorca also follow. The Spanish Ministry of Health publishes annual reports on water quality in pools.

Measure the values at least twice a week during the season. Electronic testers are more accurate than test strips, but strips are fine to start with as long as you measure regularly.

Cloudy or green water: causes and first aid

Green water is almost always an algae problem, and on Mallorca it usually has one of these causes:

1. Too little free chlorine: broken down by heat and sun faster than it is replenished.
2. Over-stabilization: too much cyanuric acid blocks the chlorine that is there.
3. pH above 7.6: the disinfecting effect of the chlorine drops drastically.
4. Filter run time too short: in summer the pump should run 8 to 10 hours a day.
5. Sahara dust: after Calima weather, the dust brings nutrients into the water.

First aid always follows the same order: lower the pH to 7.0 to 7.2, then shock-chlorinate, let the pump run for 24 to 48 hours, vacuum the dead algae off the floor, and backwash the filter. Milky, cloudy water without a green tinge, on the other hand, is often a lime or filter problem: check the pH and use a flocculant.

How do I get green pool water clear again quickly? First lower the pH to 7.0 to 7.2, then shock-chlorinate and run the filter pump for 24 to 48 hours without a break. Then vacuum the floor and backwash the filter. In most cases the water is clear again after two to three days.

DIY or maintenance contract: the annual costs

Whether a maintenance contract pays off is in the end a math exercise plus an honest answer to the question of whether you really want to test and dose twice a week in high season. For a typical private pool of 40 to 50 cubic meters, the annual costs look roughly like this:

Doing it yourself therefore saves 500 to 2,000 EUR a year depending on the pool. In return, a good pool company not only handles the chemicals but also spots wear on the pump, filter, and pipes before it turns into expensive repairs. Especially for owners who are not on the island permanently, the contract is usually the less stressful choice: a pool that has turned over the course of weeks quickly costs more in chemicals, water, and labor than half a year of maintenance.

Conclusion

For pool water treatment on Mallorca there is no way around chlorine in some form: either dosed the classic way or conveniently produced by salt chlorination. Active oxygen alone is no match for the island temperatures, and UV systems are a good addition for reducing chemicals. More important than the method are stable values: pH between 7.0 and 7.4, free chlorine between 0.5 and 1.5 mg/l, and cyanuric acid under control. If you measure regularly, you can get by with 400 to 800 EUR a year doing it yourself; if you want peace of mind or are not permanently on site, you are better off with a maintenance contract from around 1,000 EUR a year. Our guide to running and operating costs on Mallorca gives you an overview of all the ongoing costs around house and pool.