Real-life case: salt pool gone green (the chlorinator isn't magic)
- The situation: a salt pool reputed to be 'trouble-free', gone green in mid-season.
- Myth debunked: salt doesn't dispense with maintenance — the chlorinator makes chlorine, but the pH, the cell and the stabiliser decide how effective it is.
- Causes here: pH risen too high (typical of salt) + a scaled-up cell that no longer produced enough.
- Cell cleaning + pH corrected + shock → clear water, and monitoring that held.
“We switched to salt precisely so we’d never see this again.” The sentence sums up the disappointment. The salt pool carries a reputation for absolute serenity — “you add salt and you forget” — so when the water turns green in the middle of July, the bafflement is total. Yet the chemistry is unmoved: a salt pool can turn green exactly like any other. Here’s why, on a real case, and how the pool became clear again.
The great salt misunderstanding
Let’s say it again, because it’s the root of the problem: a “salt” pool is a chlorine pool. The chlorinator makes chlorine continuously from the dissolved salt — it’s convenient (steady production, no tablets to handle), but it’s still chlorine, subject to the same laws. And three things can cut off the tap without warning: a drifting pH (salt structurally raises it, and at high pH the chlorine produced works poorly), a scaled cell (a limescale deposit holds it back, production drops), or a production setting too low for the season.
On this pool, the test showed the winning combo of trouble: pH at 7.9 (never corrected since spring) and a cell coated in white scale that produced only a fraction of its capacity. Chlorine had been running short for days with nothing to flag it — the chlorinator was running, the display was green, but the water was turning.
The recovery and restarting the cell
Three fronts in parallel. The cell first: removed, descaled (with the limescale deposit gone, production resumed). The pH next, brought back towards 7.2 — and there, the key lesson of salt: it will need close watching, because it will rise again. The chlorine last: since the chlorinator alone would take days to recover green water, a manual top-up shock chlorination gave the boost, dosed on the volume. Continuous filtration, and clear water in 48 h.
Detail checked along the way: the salt level. Too low, the cell can’t produce, even when clean — it’s the other silent cause of salt pools that “no longer sanitise”.
The monitoring that changed the game
The salt pool doesn’t ask for less attention — it asks for a different kind: less product handling, but tighter pH monitoring and an eye on the cell. Since then, the ritual comes down to two moves: photo test twice a week (the pH especially) and a visual check of the cell each month. The app tracks the pH, warns when it drifts, and reminds you of the cell maintenance. The “trouble-free” the seller promised has finally come true — because it was being monitored.
What this case teaches
Salt automates the production of chlorine, not the maintenance of the water. Believing it dispenses with testing exposes you to the worst kind of green water: the one that arrives “even though everything looked normal”. The real points to watch on a salt pool — pH, cell, salt level — are few and easy to track. The app monitors them for you and, the day it turns anyway, calculates the right top-up chlorination: salt and the app, together, truly deliver the promise of peace of mind.
Frequently asked questions
Can a salt pool really turn green?
Yes, like any pool. Salt isn't a magic sanitiser: the chlorinator turns salt into chlorine, but if the pH drifts, if the cell scales up or if production is too low, the chlorine runs short and the algae move in.
Why does the pH keep rising on a salt pool?
Electrolysis tends to raise the pH structurally. It's normal and well known: a salt pool needs even more regular pH monitoring than a classic chlorine pool, and more frequent corrections.
What do I do if the chlorinator no longer produces enough chlorine?
Check the salt level first (too low, the cell doesn't produce), then the scaling of the cell (a white limescale deposit holds it back), and the production run time setting. A scaled cell can be cleaned; in the meantime, manual top-up chlorination tides you over.