How to Clean a Salt Chlorinator Cell Safely

A salt chlorinator is one of the most convenient things you can fit to a pool. It makes chlorine from salt dissolved in the water, so there is far less handling of chlorine by hand. But it is not maintenance-free. The cell, the part that actually makes the chlorine, slowly collects scale, and a scaled cell makes less chlorine while the control box carries on looking perfectly normal. Many green pools with a working chlorinator come down to exactly this. Here is how to tell when your cell needs attention and how to clean it without damaging it.

If you are still deciding whether salt is right for your pool, start with our comparison of salt chlorinators and traditional chlorine.

Why chlorinator cells scale up

Inside the cell is a stack of thin metal plates. When the chlorinator is running, a low-voltage current passes between the plates through the salty water, and that electrolysis turns some of the salt into chlorine. The same process makes the water right at the surface of the plates more alkaline, and in alkaline water dissolved calcium comes out of solution as a hard white deposit. That deposit is scale.

Several things make it worse:

  • Hard water. Municipal water across Gauteng carries a fair amount of calcium, and every top-up after evaporation adds more.
  • High pH. Salt pools tend to drift upwards in pH, and scaling speeds up as pH rises.
  • High total alkalinity and calcium hardness. Both push the water towards depositing scale.
  • Warm water. Scale forms more readily in a heated pool or in midsummer.

Keeping pH and alkalinity in range is the single best way to slow scaling down. Our guide to pool water balance on the Highveld explains how to read and correct each of these levels.

Signs your cell needs cleaning

  • A white or grey crust is visible on the plates, or flakes of scale sit in the bottom of the cell housing
  • The pool needs extra chlorine by hand to hold a reading, even though the chlorinator is set as before
  • The free chlorine reading keeps drifting down, especially in hot weather
  • The control box shows a check-cell, low-output or low-salt indicator
  • There are few or no fine bubbles from the cell when the pump is running and the chlorinator is on

A word on the low-salt light. On many units, the salt reading is worked out from how easily current flows through the cell. A heavily scaled cell can therefore report low salt when the salt level in the water is actually fine. Before adding salt because of a warning light, test the water and clean the cell if it is scaled.

Check the salt level first

Every chlorinator has its own recommended salt range, and it is printed in the manual. Check your chlorinator's manual for the correct figure and test the water with salt test strips or a meter. Too little salt makes the cell work harder and produce less; too much wastes money and can trigger a high-salt warning. Add salt in stages, with the pump running, and let it dissolve and circulate before testing again.

How to clean a chlorinator cell, step by step

Before you start, read the cleaning section of your chlorinator's manual. Some manufacturers specify a particular cleaning solution, dilution or soak time, and some cells come with a cleaning stand or cap. Their instructions take precedence over anything general, including this guide.

You will need rubber gloves, eye protection, a plastic bucket or the cleaning stand, clean water, and the acid or cleaning solution the manual specifies. Work outdoors, in a well-ventilated spot, away from children and pets.

  • Switch everything off. Turn off the chlorinator control box and the pool pump, and isolate them at their switch or isolator so nobody can switch them on while you work.
  • If the equipment sits below the water level, close the valves either side of the cell so the pool does not drain through the open pipe.
  • Unplug the cell cable from the control box or the cell terminals, and unscrew the cell unions to remove the cell. Keep the O-rings safe.
  • Inspect the plates. Look through the cell at the plates. Light scale, or loose flakes, can often be rinsed off with a garden hose. If that clears it, you may not need acid at all.
  • Never scrape the plates with a screwdriver, wire brush or anything hard. The plates carry a thin coating that makes the chlorine, and scratching it shortens the life of the cell.
  • If scale remains, prepare the diluted acid solution the manual specifies. Always add acid to water, never water to acid, and never mix acid with chlorine products.
  • Stand the cell upright in its stand or cap, or in the bucket, and pour in the solution until the plates are covered. It will fizz as the scale dissolves.
  • Leave it only as long as the manual says, or until the fizzing stops. Do not leave a cell soaking longer than necessary, as that also wears the coating.
  • Pour the used solution out carefully where it will not harm plants or run into a stormwater drain, and rinse the cell thoroughly with clean water.
  • Check the O-rings are seated and undamaged, refit the cell, reconnect the cable and open any valves you closed.
  • Switch the pump on first, check for leaks, then switch the chlorinator back on and confirm it is producing bubbles and showing a normal reading.

How often should you clean the cell?

There is no single interval that suits every pool. Inspect the cell regularly, every month or so is a sensible habit, and clean it when you see scale forming, following your manual. A pool with hard water, high pH or heating will need it more often than a well-balanced, unheated pool. If you are cleaning the cell very frequently, the real problem is almost always the water balance, not the cell.

Self-cleaning and reverse-polarity cells

Many modern chlorinators periodically reverse the polarity of the plates. This helps shed scale as it forms and reduces how often you need to clean the cell by hand. It does not stop scale altogether, particularly in hard water or with high pH, so a self-cleaning cell still needs looking at from time to time. The manual will say how the reversing cycle is set and whether you should adjust it for your water.

When the cell is worn out

A cell does not last for ever. The coating on the plates wears away gradually with use, and once it has gone the cell produces little chlorine however clean it is. Signs that a cell is near the end of its life:

  • Output stays low after a thorough clean, with the salt level correct
  • Patches of the plates look bare, dull or discoloured compared with the rest
  • The coating appears to be peeling or flaking
  • The control box keeps showing a check-cell indicator after cleaning

A worn cell can be replaced on its own on many models. If the unit is old or parts are hard to find, a new unit may make more sense. The salt chlorinators in our online shop can be installed at a fixed fitting price.

Our chlorinator service

If you would rather not handle acid, or the cell is not responding to cleaning, our chlorinator service is R1,299. It covers cleaning the cell and inspecting the unit: the plates, the flow switch, the connections and the control box readings. We check the salt level in the water as well. The service is part of our pool repairs work, which also covers valves, lights and fittings.

Pools on a weekly maintenance plan have the chlorinator checked as part of each visit, which is often where a scaled cell is caught before the pool turns green.

Getting help

If your chlorinator is on but the pool keeps losing its chlorine, WhatsApp us on 081 577 5051. Send the make and model of the chlorinator, a photo of the cell and the control box display, and your latest water test if you have one. That is usually enough for us to tell you whether it is a cleaning job, a water balance problem or a worn cell.

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