| Cause | How to Confirm | Fix |
|---|---|---|
| Salt level too low | Test with salt strips or digital meter | Add pool-grade salt to reach 3,200 ppm |
| Cell needs cleaning (calcium scale) | Inspect cell plates — white calcium deposits visible | Acid soak (4:1 water:acid, 15–20 min) |
| Water temperature too cold | Check water temp — below 60°F? | Supplement with liquid chlorine |
| Output set too low | Check controller — output % setting | Increase output % or daily run hours |
| Cell worn out / failed | No chlorine at 100% output with correct salt and clean cell | Replace cell ($200–$700) |
Salt chlorine generators require a specific salt concentration — typically 2,700–3,400 ppm — to function. The system uses electrolysis to split sodium chloride into chlorine, and insufficient salt means insufficient electrolyte for the reaction.
Most controllers display a low-salt alert when concentration drops below 2,500 ppm, but production may be reduced at any level below the optimal 3,200 ppm range. Test salt level monthly with pool-grade salt test strips or a digital salt meter (more accurate than strips). Add pool-grade sodium chloride — plain non-iodized salt without anti-caking agents.
The electrolytic cell contains titanium plates coated with a precious metal catalyst. As water flows through the cell, calcium carbonate deposits on these plates over time — especially in hard water or high-pH pools. Heavy calcium buildup insulates the plates, reducing or stopping electrolysis.
Inspect the cell quarterly (or when the "inspect cell" light illuminates): remove the cell and look through it toward a light source. White, crusty deposits coating the plates indicate scaling. Clean with a 4:1 water-to-acid soak (muriatic acid), rinsing thoroughly before reinstallation. Never use metal tools or high-pressure sprayers directly on the plates — the precious metal coating is thin and can be damaged.
SWG cells rely on electrolysis, which becomes less efficient as water temperature drops. Most residential salt systems significantly reduce output below 65°F and shut off entirely below 50–55°F (many systems display a "low temperature" or "inactive" status in cool conditions).
If you swim in shoulder seasons (spring/fall) with cool water, supplement the salt system with liquid chlorine or tablets to maintain adequate free chlorine. The salt system will resume normal production as water warms in spring.
Salt chlorinators produce chlorine at a percentage of maximum output for each cycle. If output is set to 20–30%, the system may produce far less than pool demand requires — especially during high-use periods, hot weather, or when the pool has elevated organic load.
Check the output percentage on the controller display. During peak summer, most pools need 50–80% output. If you're seeing green water or chronically low chlorine with the cell clean and salt level correct, increase the output percentage in 10% increments until chlorine stabilizes at 1–3 ppm.
The most common SWG mistake: pool owners assume the salt system handles everything without checking it. Salt cells need inspection and cleaning every 3–6 months, salt level testing monthly, and output adjustment seasonally. They are low-maintenance compared to manual chlorination — but not zero-maintenance.
Salt cell plates degrade over time. The precious metal catalyst coating erodes with each use cycle, and after 3–7 years (depending on run hours, water quality, and cleaning frequency), the cell produces progressively less chlorine despite correct salt level and settings.
Signs of cell failure: chlorine output is low even at 100% setting with correct salt and clean plates; the cell doesn't pass the 100%-output test (no elevated chlorine at return jet); the controller shows error codes. Cell replacement cost: $200–$700 depending on brand and model.
PoolLens logs salt level, free chlorine, and cell inspection dates so you can see when your salt system is trending toward underperformance — before it causes a water quality problem. Set inspection reminders and track cell age.
Open PoolLens Free →Set output to 100%, run the pump for 30–60 minutes, then test chlorine at the return jet with a drop kit. A working cell produces elevated chlorine at the return. If no generation at 100% output with correct salt and clean cell, the cell may be failing. Check controller diagnostics for error codes.
Remove the cell from the plumbing. Mix 4 parts water to 1 part muriatic acid. Soak only the cell plates (not the electronics) for 15–20 minutes until calcium deposits dissolve. Rinse with fresh water. Reinstall. Clean every 3–6 months or when the inspect-cell light illuminates.
Most systems require 2,700–3,400 ppm, with 3,200 ppm as the optimal target. Below 2,500 ppm, most systems reduce output or stop producing and display a low-salt alert. Test monthly with pool salt strips or a digital salt meter. Use non-iodized pool-grade salt.
Significantly. Output decreases 30–50% below 65°F and most systems shut off entirely below 50–55°F. In cool shoulder seasons, supplement with liquid chlorine. The system resumes normal output as water warms.
Typical lifespan is 3–7 years, depending on run hours, water quality, and maintenance frequency. Regular cleaning extends cell life significantly. Signs of end-of-life: declining chlorine output despite correct salt and settings, frequent error codes, and visible plate erosion. Replacement cost is $200–$700.