Your pump is running, the chlorinator looks normal, and yet free chlorine is sitting at zero. You test again an hour later and get the same result. Meanwhile, the water is starting to look murky and you're not sure whether you're facing a simple fix or a bill for a new system. If your pool is not making chlorine, the good news is that most causes are fixable, and diagnosable, without calling a technician.
Many salt pools that stop producing chlorine have one of a handful of common, fixable causes. The same problems come up again and again, and most of them don't require a new chlorinator. What you need is a clear diagnostic path. Work through salt level, flow, cell condition, error codes, stabiliser, and then finally the cell itself, in that order, before drawing any conclusions.
Salt level: start here before anything else
Low or incorrect salt is the single most common cause of a salt pool not producing chlorine, and it's often the easiest to fix. Most salt chlorinators operate in the 2,700, 3,400 ppm range, with 3,200 ppm a widely cited sweet spot. Brand-specific targets vary: Pentair IntelliChlor works best around 3,000, 3,400 ppm, while systems like CircuPool accept 2,500, 3,500 ppm. What catches many people out is that both too-low and too-high salt readings cause the unit to stop production, so from the surface they look identical.
Cold water is another trap. When water temperature drops, the chlorinator's onboard sensor can drift and show a low salt reading even when the actual salinity is perfectly fine. Never rely solely on your control panel reading to make a salt decision. Use a dedicated salt test strip or a digital salinity tester as your primary reference. If the panel says low but your test kit confirms salinity is in range, move on to checking the cell for scaling (covered in the next section). If salt genuinely is low, calculate your pool's volume and dose incrementally rather than guessing.
How to test salt accurately
Dip a salt test strip into the pool water at elbow depth, away from return jets. Hold it still for the recommended time (usually 30 seconds), then compare against the colour chart. For a more reliable result, use a digital salinity tester and calibrate it to your water temperature before reading. Take readings from two or three spots in the pool and average them, salinity can stratify if the pool hasn't been circulating long enough.
Why your pool is not making chlorine: flow and pump runtime
Every salt chlorinator has a flow switch or sensor built in. When water movement drops below a minimum threshold, typically around 75, 115 litres per minute (20, 30 GPM) depending on the model, as specified in manufacturer documentation, the unit shuts off production entirely to protect the cell. This can happen silently, with no dramatic warning, or the panel might flash a "No Flow" or "FLO" indicator. Common causes include a clogged filter, blocked skimmer or pump basket, a partially closed valve, air trapped in the line, or a variable-speed pump running on its lowest setting.
Pump runtime is just as important and is frequently overlooked. The cell only generates chlorine while the pump is running, so if your daily runtime is too short, you'll consistently fall short of your chlorine demand. This holds true even when everything else is working correctly. A practical starting point for Australian summers is eight hours per day minimum, moving toward ten to twelve hours in peak heat or with heavy pool use. One common rule of thumb is one hour of runtime per roughly 5.5°C of ambient temperature, in a Queensland summer sitting above 30°C, that translates to eight or more hours daily. Adjust this estimate to suit your local conditions. Check your timer settings before pulling the cell for inspection.
Water temperature is the third factor in this group. Most salt chlorinators reduce output noticeably below about 15°C and many models shut down entirely somewhere between approximately 10, 16°C, depending on the brand and model. Check your manufacturer's specifications for the exact cutoff. This is normal behaviour, not a fault. In southern Australian states over winter, this means supplementing with liquid chlorine during cooler months rather than pushing the chlorinator to compensate.
A scaled or dirty cell can look exactly like a dead one
Calcium build-up on the titanium plates is one of the most misdiagnosed problems in saltwater pools. Pool owners remove the cell, see white or grey crusty deposits, and assume the worst. A scaled cell is not a dead cell; it needs cleaning. The scale interferes with the electrical current flowing between plates, which reduces chlorine output and can cause the control panel to report false low-salt readings or trigger a "Check Cell" warning.
To confirm whether the cell is actually producing, run the system at 100% output for 30 minutes, then test free chlorine directly at a return jet and compare it with a sample from a still area of the pool. A functioning cell should show at least 2 ppm more free chlorine at the return. If those readings are the same, production is compromised.
How to clean a chlorinator cell
A diluted acid wash works effectively for most scale build-up. Mix one part hydrochloric acid into ten parts water, always add acid to water, never the reverse, soak the cell plates for 10, 15 minutes, and rinse thoroughly. Stop the soak when bubbling slows. Wear gloves and eye protection, work in a well-ventilated area, and keep the electrical housing dry throughout. After cleaning, run the system again and recheck; if the same error codes return within minutes despite correct salt and flow, the issue lies elsewhere.
Some cells are designed with a self-cleaning function: reverse-polarity cells automatically switch the charge direction during operation, which slows scale build-up and reduces how often manual cleaning is needed. If your chlorinator includes this feature, check the manual for the recommended cleaning interval, as it will typically be longer than for a standard cell.
If your pool is not making chlorine, check what the error codes mean
Error codes look alarming but most of them point to something straightforward. A "Low Salt" or "Check Salt" warning means either salinity is genuinely below target, or the cell is scaled and reading falsely low. Always verify with an independent test before adding salt. A "No Flow" or "FLO" warning means the flow switch isn't detecting water movement; check the pump, filter, and all valves before assuming the switch itself has failed.
A "Check Cell" or "Inspect Cell" indicator is usually a maintenance reminder triggered by an internal timer, not a hard fault. Clean the cell and reset the indicator per your manual. Brand-specific codes break down as follows:
- Hayward AquaRite:Code 125 means the cell needs cleaning; Codes 144 and 145 indicate low or high salinity respectively; Code 172 points to a sensor or flow issue.
- Intex systems: Code 90 is a flow fault, Code 91 is low salt, and Code 92 is high salt.
- Pentair iChlor: A persistent FLO error can be cleared with the sequence LESS, MORE, MORE, LESS, LESS, LESS.
The key diagnostic rule: if a code clears after you address the underlying cause, clean the cell, correct the salt, unblock the filter, the system was working as designed. If the same code returns immediately after doing everything correctly, you're dealing with a failing cell, a faulty flow switch, or a damaged sensor. A reset won't solve it.
How stabiliser levels can suppress chlorine without you realising
This one catches a lot of pool owners off guard. Cyanuric acid (CYA, or stabiliser) protects chlorine from UV breakdown in outdoor pools, which is genuinely useful. The problem is that as CYA climbs, it binds more and more chlorine into a less active form. Your test kit might show an acceptable free chlorine reading, but the fraction of active hypochlorous acid doing the actual sanitising drops considerably. This is sometimes called chlorine lock, and it can make a healthy chlorinator appear to be underperforming.
For saltwater pools, target 30, 50 ppm CYA and aim toward the lower end of that range. A practical ratio to keep in mind: maintain free chlorine at a minimum of 5% of your CYA level. If CYA is at 40 ppm, you need at least 2 ppm free chlorine for effective sanitation. If your CYA is above 80 ppm, effective sanitisation becomes impractical regardless of how much chlorine you add; partial drain and dilution with fresh water is generally required at that point. Many pool professionals recommend dilution over chemical CYA reducers, as results and cost-effectiveness from reducer products vary widely.
When the cell itself is worn out: the most cost-effective fix
If you've worked through every step above, salt confirmed correct, flow normal, cell recently cleaned, error codes resolved, CYA in range, and the pool is still not making chlorine, you're looking at a cell that's reached end of life. Most salt cells last between three and seven years depending on usage intensity, water chemistry, and cleaning frequency. Running a cell at low salt or with heavy scale build-up accelerates wear considerably.
The definitive test is straightforward. Run the system at 100% output for 30 minutes with everything else confirmed correct, then test free chlorine at a return jet. If there's no meaningful rise, the cell is exhausted. For a more precise check, a functioning cell typically shows voltage in the 23, 26 V range with consistent amps on both polarities, though exact figures vary by model, so cross-reference your manufacturer's specifications. Low or zero amps with normal voltage points to a dead or failing cell rather than a power supply problem.
The good news is that a worn-out cell doesn't mean you need a new chlorinator. In most cases, a compatible replacement cell restores full chlorine production at a fraction of the cost of replacing the entire unit. When it comes time to source a replacement, it's worth comparing compatible aftermarket options against OEM pricing, compatible cells for most major Australian brands, including Auto Chlor, Zodiac, Hurlcon, Poolrite, Clearwater, Salty Gem, and Viron, are widely available. Best Pool Chlorinators stocks a range of compatible replacement cells, with free delivery across Australia and expert support to help match the correct cell to your existing system.
Work through the list before you spend anything
The diagnostic order matters: salt level, flow and runtime, cell cleanliness, error codes, CYA, and finally the cell itself. Each step rules out the next, and most of the fixable causes sit near the top of that list. In the majority of cases where a pool is not making chlorine, the fix is something you can handle yourself in an afternoon without calling anyone.
For the cases that do come down to a worn-out cell, the path forward is straightforward. Browse the replacement cell range at Best Pool Chlorinators, use the expert support to confirm compatibility with your existing chlorinator, and get free delivery straight to your door. When your pool is not making chlorine and a new cell is what's needed, you'll have production restored well before the week is out.