Salt-water pools explained
Salt chlorination is the most popular way to sanitise a pool in South Africa — but “salt water” does not mean chlorine-free. Here is how it actually works, what it costs to run, and how it behaves in a fibreglass shell.
What a salt pool really is
A salt-water pool is still a chlorinated pool. The difference is where the chlorine comes from. Instead of you adding it by hand, a salt chlorinator makes it on site: pool salt is dissolved in the water, and as that water passes through an electrolytic cell in the plant room, the dissolved salt is converted into the same sanitiser you would otherwise buy in a bucket.
Once the chlorine has done its work it reverts to salt and the cycle starts again. That is why a salt pool needs surprisingly little salt after the initial dose — you only top it up to replace what physically leaves the pool through backwashing, splash-out, rain overflow and draining.
The water itself is only mildly saline. A salt pool runs at roughly 3,000–4,000 parts per million, about a tenth of the salinity of seawater. Most swimmers cannot taste it, and it is noticeably gentler on eyes and skin than a pool that gets shock-dosed by hand every few days.
Three steps, then it looks after itself
Ordinary pool salt — not table salt — is dissolved into the water to reach the level your chlorinator specifies. A 30,000-litre pool needs roughly 105 kg to reach 3,500 ppm. It is a once-off dose, then top-ups.
Water passing over the charged plates of the cell converts the dissolved salt into hypochlorous acid, the active sanitiser. Output is set once on the control box and generated whenever the pump runs.
After sanitising, the chlorine reverts to salt and is used again. You end up dosing acid, stabiliser and the occasional bag of salt instead of buying chlorine all summer.
Salt chlorination vs dosing by hand
Both approaches sanitise with chlorine. The choice is really about whether you would rather buy equipment once or buy chemicals continuously.
What it actually costs to run
The up-front cost is the chlorinator itself, sized to your pool volume. After that the running cost is modest: electricity while the cell is energised — the pump is running anyway — a bag or two of salt a year to replace losses, and a replacement cell every few years depending on water balance and how hard the unit is driven.
Two things shorten cell life more than anything else: calcium scaling and running the output higher than the pool needs. Keep pH in range, keep the cell clean, and turn the output down in winter when demand collapses. A cell that is looked after is one of the cheapest things in the plant room; one that is neglected is not.
Ask us for current pricing on the chlorinator we specify with your pool — we fit the size your volume actually needs rather than the biggest unit on the shelf.
Salt and a fibreglass shell
Every Cosmo shell is salt-chlorination compatible. The gelcoat surface is unaffected by salt at pool concentrations, and because it is non-porous there is nothing for salt to work into — one of the reasons fibreglass and salt suit each other so well.
What does need thinking about is everything around the water. Salt is harder on some natural stone copings, on unsealed cement and on untreated metalwork such as handrails, ladders and light surrounds. Specify salt-rated fittings, seal your coping, and hose the surround down after a busy weekend and it stops being a consideration at all.
If you are relining an older marbelite or concrete pool and want to run salt, say so up front — the interior finish and the fittings we specify change.
Frequently asked questions
No. A salt chlorinator generates chlorine from dissolved salt instead of you adding it. The sanitiser is the same; the delivery is automatic and continuous.
Most people cannot at 3,000–4,000 ppm, which is roughly a tenth of the salinity of seawater. What you will notice is that the water feels softer than a hand-dosed pool.
Usually yes. It is mostly a plant-room change plus the initial salt dose, with a check on your coping, fittings and interior finish before you commit.
Yes, weekly. The chlorinator handles the chlorine; you still watch pH, which drifts upward in salt pools, along with stabiliser and salt level.
No. The gelcoat is unaffected at pool salinity. The care goes into the surround and the metal fittings, not the shell.
Price your pool in two minutes
Every Cosmo shell is salt-ready. Get a transparent estimate online, or ask us anything on WhatsApp.