A salt cell that needs replacing typically shows one clear pattern: your pool’s free chlorine keeps dropping even though salt levels, water flow, and temperature are all normal. Most salt cells last 10,000 hours of runtime, which translates to roughly five to seven years of typical use. If yours is in that age range and chlorine production is declining despite proper maintenance, replacement is likely overdue. But before you spend $400 to $800 on a new cell, it’s worth ruling out the cheaper, fixable causes first.
The Most Reliable Sign of a Dying Cell
The single best indicator is a growing gap between what your cell should be producing and what’s actually showing up in your water. Test your pool’s free chlorine and salt level at the same time. If salt concentration is in the recommended range (typically 3,000 to 3,500 ppm) and your cell is set to a high output percentage but free chlorine remains stubbornly low, the cell’s plates are likely worn out.
This pattern tends to get worse over time. Early on, you might compensate by cranking output to 80% or 100% where 50% used to be enough. Eventually, even maximum output can’t keep up with chlorine demand, and you find yourself supplementing with liquid chlorine or shock just to maintain safe levels. That’s the clearest signal the cell has reached end of life.
Rule Out These Problems First
Several common issues mimic a failing cell, and all of them are cheaper to fix.
- Calcium buildup on the plates. White, chalky deposits on the cell’s metal plates insulate them from the water and reduce chlorine output. Remove the cell and inspect it visually. If the plates are coated, soak the cell in a diluted acid solution per your manufacturer’s instructions. A good cleaning can restore full production in a cell that still has life left.
- Low salt level. If your salt concentration drops below about 2,300 ppm, most systems will reduce or stop chlorine production entirely. Test salt independently with a liquid drop kit or test strip rather than relying solely on the control panel’s reading, which can drift with age.
- Cold water. Salt cells automatically shut down when pool water drops to around 62 to 65 degrees Fahrenheit, depending on the brand. If you’re troubleshooting in early spring or late fall, low water temperature may be the entire explanation.
- Flow sensor issues. The system needs adequate water flow to operate. A dirty filter, closed valve, or faulty flow sensor can trick the unit into thinking there’s no flow, shutting down chlorine generation even though the cell itself is fine.
What the Control Panel Tells You
Your salt system’s control panel displays diagnostic information that can confirm whether the cell is the problem. On Hayward Aqua Rite systems (one of the most common brands), you can check two key readings: voltage and amperage.
During normal chlorine production, cell voltage typically reads 22 to 25 volts. If voltage climbs to 30 to 35 volts while the system is supposedly generating chlorine, the cell is struggling. It’s drawing more electrical pressure to push current through degraded plates, similar to how a dying battery requires more effort to charge.
Amperage tells the other half of the story. A healthy full-size cell (T-15) draws between 3.1 and 8.0 amps during generation. Smaller cells have proportionally lower ranges. If amperage falls below the normal range for your cell size while salt levels test fine and the cell is clean, the plates have lost too much coating to function properly. That’s a definitive sign you need a new cell.
Many systems also have indicator lights. If both a “check salt” and “inspect cell” light stay on simultaneously, the system is telling you it can’t produce chlorine. This can mean salt is below 2,300 ppm, the cell is unplugged, or the controller is set to the wrong cell type. Check those possibilities before concluding the cell itself has failed.
How to Do a Bucket Test
A bucket test is the most direct way to confirm whether your cell can still produce chlorine. It isolates the cell from other variables like pool chemistry and plumbing issues.
Start by turning off the pump and salt system and disconnecting power. Remove the cell from its plumbing housing. Fill a clean bucket with pool water deep enough to submerge the cell’s plates but not the electrical connections. The water should have the right salt concentration, between 3,000 and 3,500 ppm.
Carefully reconnect the electrical wires to the cell (this involves handling electrical connections near water, so if you’re not comfortable, have a pool technician do this step). Power the system on and let it run for a few minutes. Then test the bucket water for free chlorine. If levels have increased, the cell still works and your problem is elsewhere in the system. If chlorine hasn’t budged, the cell needs replacing.
How Long Salt Cells Typically Last
Most residential salt cells are rated for about 10,000 hours of operation. In practice, that works out to five to seven years for a pool that runs its pump eight to twelve hours a day during swim season. Several factors push that number higher or lower.
Running your cell at consistently high output percentages wears the plates faster. If your pool demands 80% to 100% output most of the time, the cell may only last four years. Pools that stay balanced and need only 40% to 60% output get more life from the same cell. Frequent calcium buildup that requires repeated acid washes also degrades the plates over time, since each cleaning strips away a small amount of the cell’s coating along with the scale.
Oversalting your pool is another common accelerant. When salt concentration exceeds the recommended range, the cell works harder than designed, which shortens its lifespan. Keeping salt in the sweet spot protects both the cell and your pool equipment.
When Cleaning Won’t Help Anymore
There’s a point where cleaning a cell becomes futile, and recognizing that threshold saves you time and frustration. Pull the cell out and look at the plates closely. On a healthy cell, you’ll see metallic plates with a visible coating (this is the ruthenium or iridium oxide layer that enables chlorine generation). On a spent cell, the plates look visibly thinner, pitted, or bare in patches where the coating has worn away.
If you’ve cleaned the cell, confirmed proper salt levels, verified adequate flow, and the system still can’t maintain chlorine, you’ve exhausted the fixable causes. A cell in the five-to-seven-year range showing these symptoms is telling you it’s done. At that point, replacing it promptly is cheaper than continuously buying supplemental chlorine to compensate for a cell that’s producing less every week.