Salt or chlorine pool in Tulum: the well water decides

A salt pool is not a pool without chlorine: it is a pool that makes its own chlorine from dissolved salt. In Tulum the question is not which one disinfects better, it is how long the cell lasts in hard well water drawn through limestone. That answer changes the maths.

What a salt chlorinator actually does

Salt is dissolved in the water to a few parts per thousand, far less than the sea at around 35, and a cell with plates puts it through electrolysis. Out comes hypochlorite, which is chlorine. Chlorine does not leave the equation, it changes origin. What the system removes is buying and storing drums; what it adds is one more piece of equipment in the plant room, with a wear part inside.

That carries consequences almost nobody mentions at the point of sale:

• You still need the same balance. pH 7.2 to 7.6, alkalinity 80 to 120 ppm, cyanuric acid 30 to 50 ppm. The cell solves none of that.
• You still need to brush and filter. Algae start on the wall, not in the water, and no cell brushes.
• Output depends on water temperature. Below a certain temperature a cell produces less; in Tulum that is rarely the issue, but the opposite is: with water at 30 degrees and direct sun, demand climbs faster than an undersized cell can produce.
• If the pump stops, there is no chlorine. A chlorine pool holds a reserve in the water and in the floater. A salt pool stops producing the moment circulation is cut.

Where Tulum changes the maths: scale

Almost all fill water here comes from a well, and the ground is limestone. That water arrives hard, loaded with calcium. In a chlorine pool the scale is managed by keeping the balance right: calcium hardness between 200 and 400 ppm and pH between 7.2 and 7.6, which is what stops the water from scaling.

In a salt pool there is a second front. Electrolysis raises the pH of the water by its own operation, and a high pH pushes calcium carbonate to precipitate. Where does it precipitate first? At the hottest, most electrically active point in the circuit: the cell plates. A white crust forms, the usable electrode surface drops and chlorine output falls. The owner sees chlorine dropping, turns the chlorinator up, the cell runs hotter, and the crust grows faster.

That loop is the real reason a cell delivers less in Tulum than in the brochure. It is not the brand, it is the water.

And a third effect: the acid

Because pH climbs on its own, maintaining a salt pool means bringing it down with acid again and again. Done with measurement, nothing happens. Done by eye, which is what happens when the owner does not live here and somebody well-meaning adds acid every week, the water spends stretches below 7.0, aggressive, and then it attacks exactly what Tulum is full of: lime-based chukum and stucco finishes, limestone coping and steps, and the equipment hardware.

Put another way: a salt pool does not forgive the absence of measurement. Neither does a chlorine pool, but it warns you later.

The comparison, with only what can be stated

What you will not find in that table is an annual saving in pesos. We do not publish one because we have not measured it across an honest sample of Tulum pools, and the figure that circulates online comes from climates and water that are not ours. What we do have measured is our own price: salt cell cleaning costs $900 MXN and it is on the pricing page with the rest.

How to tell your cell is already scaled

Four signs, earliest to latest:

• Free chlorine will not rise even with the chlorinator at 80 or 100 per cent. The first and clearest one.
• Visible white deposit between the plates when the cell is taken out. If you can see it with the naked eye, it has been there a while.
• The unit shows an error or drops its own percentage. Many controls read the conductivity drop and report it as low salt, when it is actually scaling.
• The water starts going green at the edges even though the numbers look right at midday.

The common mistake at that point is adding salt. If the problem is the crust, adding salt will not raise output and will leave the water saltier than the unit expects. The first move is to look at the cell.

What we recommend in Tulum

• If you already run salt: stay on salt, but with a cell inspection every three months, pH measured at every visit and calcium hardness under control. It is a system that works well here as long as somebody watches it.
• If you run chlorine and you are happy: do not convert to save money. Convert if you want the feel of the water and accept maintaining one more piece of equipment.
• If the pool is small, a rooftop or a plunge pool: think twice. At 8 to 15 m3 under direct sun the water heats and evaporates fast, scale concentrates and the cell works in the worst possible scenario.
• If the pool belongs to a condominium or a hotel: salt is convenient because it avoids storing product, but it demands logging discipline. With no log the cell dies silently. That is how we handle it in condo and HOA pools and in hotel pools.

What we do with a salt pool

Our weekly maintenance covers the same work as on a chlorine pool — brushing, vacuuming, backwashing, readings — plus three things specific to the system: checking that real output matches the unit setting, measuring salinity so corrections are not blind, and inspecting the cell quarterly. If it is scaled, the cleaning costs $900 MXN and we tell you before doing it.

The ranges we hold and the reasons behind them are in the chlorine and pH guide. If what is happening to you is that the water has already gone green, that gets solved first: why a pool turns green and how it is recovered.

Rather we handled it?

We provide weekly maintenance across the 25 areas of Tulum and the Riviera Maya from $1,500 MXN/month, chemicals included and crystal-clear water guaranteed. Message us on WhatsApp with a photo of your pool.