Salt Chlorinator Not Working? 10 Checks to Make
When a salt chlorinator is not working, the first sign is usually the pool, not the machine. The water goes dull, the chlorine test reads low, or a green tinge appears in the corners, while the control box sits there with its lights on as if nothing is wrong. A salt chlorinator not producing chlorine is seldom a dead unit. Far more often it is a flow problem, a salt reading, cold water or a setting. Work through these checks in order, from the simplest to the ones that point at the equipment itself.
This is a fault-finding list. If you already know the cell is scaled, our step-by-step guide to cleaning a salt chlorinator cell covers that job on its own.
Safety first: switch off at the DB
A chlorinator runs on mains power through its control box, and the cell sits in the plumbing with water running through it. Before you unplug the cell cable, remove the cell or open the control box housing, switch the chlorinator and the pump off at the distribution board, not only at the timer or the front switch. A timer can switch the pump back on while your hands are on the equipment. Never open the control box itself; the electronics inside are for a technician.
1. Is the pump running, and is there flow?
A chlorinator only makes chlorine while water flows through the cell. Most units have a flow switch or flow sensor that stops the cell when there is no flow, because running a cell dry can damage it. So if the pump is off, the chlorinator is off too, whatever its lights say.
Check that the pump timer is set correctly and that the pump is actually running. Then check what limits flow: a full weir basket, a full pump basket, a dirty filter or a pump that has lost its prime. If the pump runs but the chlorinator shows a no-flow or flow indicator, the flow switch may be stuck with debris, or the valves may be set so that little water reaches the cell. Look at the cell with the pump running; on a clear-bodied cell you should see water moving and fine bubbles coming off the plates once the chlorinator is on.
2. Test the salt level yourself
The low salt light is the warning homeowners see most, and it is the one most often misread. Many control boxes do not measure salt directly. They estimate it from how easily current passes through the cell, and that also changes with water temperature and with scale on the plates. So the panel can say low salt when the salt in the water is perfectly fine.
Test the water with salt test strips or a salt meter, or bring a sample to us. Compare the result with the range printed in your chlorinator's manual. If it really is low, add salt in stages with the pump running, let it dissolve and circulate, and test again before adding more. Rain, backwashing and splash-out all lower it over time. Never add salt on the panel's word alone; too much triggers a high-salt warning.
3. Cold water reduces output
On the Highveld, winter water gets properly cold, and chlorinators make noticeably less chlorine in cold water. Many units reduce their output or stop altogether below a set water temperature to protect the cell, and some show a cold-water indicator. The cold also makes the salt reading less reliable.
The good news is that a cold pool needs less chlorine anyway, because algae grows slowly in winter. If your pool is clear and the chlorine reading is low but steady, this may simply be winter. If the water is turning, give it a manual dose of chlorine to hold it until the water warms, and check your manual for the temperature range of your model.
4. Check pH and stabiliser
A chlorinator can be making chlorine perfectly well while the pool still tests low. Two water balance problems cause most of this.
- pH too high. Salt pools tend to drift upwards in pH. At high pH, chlorine works much less effectively, so the pool behaves as if there is not enough of it. High pH also speeds up scaling on the cell.
- Stabiliser (cyanuric acid) too low. Sunlight breaks down unprotected chlorine quickly. Without enough stabiliser, the chlorine the cell makes in the morning can be gone by the afternoon. Far too much stabiliser causes the opposite problem and weakens the chlorine.
Test pH, total alkalinity and stabiliser, and correct them before you decide the chlorinator is at fault. Our weekly pool maintenance visits test and balance the water on every visit, which is where these slow drifts are usually caught.
5. Look at the cell for scale
Pull the cell, with the power off at the DB, and look through it at the plates. A white or grey crust, or flakes sitting in the housing, means the cell is scaled. Scale insulates the plates, cuts chlorine production and can trigger the low salt light described above. Cleaning it is a separate job with its own safety steps, so follow the cell cleaning guide linked at the top of this post, or your manual, rather than improvising with acid.
6. Check the output setting and the run time
The output dial or setting may have been turned down during winter, after a party or by someone in the household, and never turned back up. Some units also have a boost or super-chlorinate mode that times out and drops back to a lower setting.
Run time matters just as much: if the pump timer was shortened to save electricity, the cell has fewer hours to make chlorine. In summer, with more sun, more swimmers and warmer water, the pool usually needs more pump hours, not fewer. Increase the run time or the output in small steps and give it a few days before judging the result.
7. Read the error lights, then read the manual
Every brand uses its own lights and codes, and they are not interchangeable. In general they fall into a few groups: salt high or low, no flow, cell check, water temperature, and a general fault. Write down exactly which light is on, or take a photo of the display, and look it up in the manual for your make and model. A cell check light that stays on after the salt, flow and scale have all been checked usually points at the cell or the control box itself.
8. Power cuts and load-shedding
A power cut stops the pump and the chlorinator together. When the power returns, check three things: that the timer still shows the correct time, that the pump has primed again, and that the chlorinator has come back on at its normal setting. Some control boxes return to a default setting after losing power. Repeated cuts also shorten the effective run time, which means less chlorine over the day. If the unit is dead after an outage, check the plug and the isolator, and leave the inside of the control box alone.
9. Is the cell near the end of its life?
The plates in a chlorinator cell carry a coating that does the actual work, and it wears away gradually with use. Once it has gone, the cell produces little chlorine however clean it is and however much salt is in the water. Signs of a worn cell:
- Output stays low with the salt, flow, temperature and water balance all correct
- The plates look bare, dull or patchy compared with how they looked when new
- A cell check indicator keeps returning after cleaning
- The cell is several seasons old and has been cleaned hard many times
On many models the cell can be replaced on its own. Our shop lists replacement chlorinator cells; send us the make and model first so we can confirm which cell fits.
10. Rule out a demand problem
Sometimes the chlorinator works, but a storm, a pool party or heavy leaf fall uses chlorine faster than it can make it. Shock the pool by hand to catch up, then let the chlorinator hold it. If you are still weighing up salt against dosing by hand, our comparison of salt chlorinators and traditional chlorine explains where each one fits.
When to call a technician
Call us when you have worked through the list and the pool still will not hold chlorine, when the control box shows a fault that the manual says needs a technician, when the unit is completely dead with power at the plug, or when you see burn marks, a melted connector or water inside the control box. Do not keep resetting a unit that trips or smells of burning.
Our chlorinator service is R1,299. It covers cleaning the cell and inspecting the unit, including the flow switch, the connections and the control box readings, and we test the salt and water balance at the same time. It is part of our pool repairs work, and parts are quoted before they are fitted. A call-out to inspect or diagnose is R650. Deducted from your quote when you accept it.
WhatsApp 081 577 5051 with the make and model of the chlorinator, a photo of the control box display, and your latest water test if you have one. That is often enough for us to tell you whether it is the water, the cell or the unit.