Salt water sounds like a holiday brochure. In a rented villa it means an electrolysis cell, a pallet of salt in the garage and a different set of bills. The water is softer on the skin. The maintenance is not free.
A salt pool is a chlorine pool with a small factory attached. The electrolysis cell sits in the return line, gets a low-voltage current and splits sodium chloride into chlorine and sodium hydroxide. The chlorine does the work. The salt is the raw material, not the cleaner.
The salinity is about 4 to 5 grams per litre, or 0.4 to 0.5 per cent. Sea water is around 3.5 per cent, so this is roughly one seventh as salty. A 50 cubic metre pool needs 200 to 250 kilograms of salt at the first fill. That is five or six 25 kilogram bags, and they do not dissolve in ten minutes.
Electrolysis pushes pH up. Left alone, the water drifts above 7.8, chlorine stops working properly and the cell scales up. You need acid, either manual dosing or a controller with a peristaltic pump. The numbers to watch are pH around 7.2 to 7.6, free chlorine 1 to 3 parts per million and salt near the cell maker's figure.
Cyanuric acid is the other quiet problem. It protects chlorine from sunlight, which is useful in Catalonia, but it does not evaporate. Top it up season after season and it climbs past 80 or 100 parts per million, and the chlorine becomes lazy. The fix is partial draining and refilling, which is exactly what drought rules can make difficult.
Converting a chlorine pool to salt usually runs €600–1,500, depending on the cell capacity, the controller and whether the pipework needs changing. The cell itself is a consumable. It lasts three to seven years, less in a hard-water area or with poor pH control, and a replacement in Spain is commonly €300–600, with larger models or branded units past €900.
Chemicals drop to roughly €100–180 a year against €200–400 or more for a chlorine pool, but the service contract does not disappear. A weekly visit in the Maresme is typically €80–150 a month, and €100–200 is normal once the pool is large or the technician comes twice a week. The pump still uses most of the electricity: 0.75 to 1.5 kilowatts for six to eight hours a day, which at €0.24 per kilowatt hour is roughly €1.10 to €2.90 a day.
This is the part the brochure leaves out. Salt spray settles on travertine, limestone, sandstone and marble coping, and over a few seasons it pits the surface. It attacks stainless steel handrails, aluminium window frames, the pool cover mechanism, gate hinges and the car parked within range. Rinsing the coping with fresh water once a week helps. Sealing the stone helps more, but it has to be redone.
A salt pool two streets from the sea is a harsher environment than the same pool inland. Check the handrail, the ladder, the cover rails and the hinges at the viewing, not after the first winter. Rust streaks on a stainless ladder are a negotiating point, not a detail.
Article 21 of the LAU keeps the installations and the equipment needed to enjoy the home with the owner. A failed cell, a cracked filter housing or a pump that dies are repair items. The tenant's side is the daily routine: skimming, emptying the basket, checking the cell, backwashing, keeping the salt level and not storing acid next to the salt bags.
Put the split in the contract. Who buys salt and acid, who tests the water and how often, whether the service is included, the age of the cell and the date of the last replacement, what happens if the pool cannot be used for a week, and who pays the electricity for the pump. A pool that is green in August is not a small inconvenience when you are paying for a villa.
A pool loses three to eight millimetres of water a day in a hot Maresme July, more when it is windy. A cover cuts most of that, and it also keeps the heat in and the leaves out. Refilling is not automatic: the Catalan drought rules set what is allowed by water system and by phase, and a private pool may be limited to a minimal top-up. Ask what the current phase allows before you sign a lease with a pool you intend to use every day.
Below about 15 °C the cell produces little chlorine, so winter maintenance often moves back to tablets or liquid. On the coast frost is rare, which is why many pools are left open all year. If the owner closes the pool from October to May, the lease should say so, and the rent should reflect it.
A salt pool is a good thing when the cell is documented and the stone is protected. It is a bad thing when the seller says solo hay que echar sal and the cell is eight years old. The water will tell you in August. The invoice tells you now.
We know which pools are serviced, which cells are due for replacement and what the lease should say before you take the keys.
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