Salt-Water Pool Basics: How a Salt Cell Works
By The Aqualitx team at STEMania · Updated
A salt-water pool is a chlorine pool. The difference is where the chlorine comes from: instead of pouring it in, a salt chlorine generator (SWG, or salt cell) makes it from dissolved salt while the pump runs. Done right, it means steady chlorine with very little daily work.
How it works
Water flows through the cell, where a low-voltage current turns some of the dissolved salt into chlorine. The chlorine sanitizes, breaks down, and turns back into salt — so the salt mostly isn't used up. You only add salt to replace what leaves with splash-out, backwashing, leaks and rain overflow.
Levels a salt pool needs
- Salt: whatever your cell's manual says — commonly 3,000–3,400 ppm. Too low and the cell stops producing; too high can trigger errors and corrode metal.
- CYA: 60–80 ppm. Higher than a non-salt pool, because the cell keeps producing all day, so the extra stabilizer protects chlorine without leaving the pool short.
- Free chlorine: the same rule as any pool — at least 7.5% of CYA, so about 4.5–6 ppm at 60–80 CYA.
- pH: 7.4–7.6. Salt pools drift up (below).
Adding salt
About 8 lbs of pool salt per 10,000 gallons raises salt by roughly 100 ppm (1 lb adds about 12 ppm). Use pure pool-grade salt, broadcast it in the shallow end, brush it until it dissolves, and turn the cell off for about 24 hours while it mixes. Then re-test with a salt test, not just the cell's own reading — cells drift.
Why pH keeps rising
Making chlorine in the cell raises pH, so salt pools need acid regularly — often weekly. Running alkalinity near the low end of its range (around 70–80 ppm) slows the climb. See how to lower pool pH.
Cell upkeep
- Scale: calcium builds up on the cell plates, especially in hard-water areas. Inspect it every few months and clean it per the manual (usually a mild acid soak) when you see white crust.
- Output setting: adjust the percentage to hold your free chlorine target. Raise it in hot, busy weeks; lower it in cool ones.
- Temperature: most cells stop producing when the water is cold (around 50–60°F). Add liquid chlorine instead until it warms.
- Lifespan: typically 3–7 years. Falling output at normal settings is the sign it's wearing out.
Shocking a salt pool
A salt cell can't make chlorine fast enough to shock. Use liquid chlorine, and turn the cell down or off while you do so it doesn't overshoot. See how much shock does my pool need.