A saltwater pool does not use salt instead of chlorine: a salt chlorine generator (salt cell) turns dissolved salt into chlorine by electrolysis. The cell only works within a narrow salt range, usually 2,700 to 3,400 ppm, so you need to know how much salt to add when you fill the pool or after rain and splash-out dilute it.
The formula
Salt (lb) = pool volume (gal) × 8.34 × (target ppm − current ppm) ÷ 1,000,000
A gallon of water weighs 8.34 lb, and ppm means pounds of salt per million pounds of water. The calculator rounds up to whole bags and shows the level you will reach with those bags.
Example
A new 15,000 gallon pool with no salt, aiming for 3,200 ppm, needs 15,000 × 8.34 × 3,200 ÷ 1,000,000 = 400 lb of salt: 11 bags of 40 lb, for $88 at $8 a bag. Eleven whole bags bring the pool to about 3,500 ppm, still within most generators’ range.
Recommended levels
| Generator | Typical range | Ideal |
|---|---|---|
| Most residential cells | 2,700 to 3,400 ppm | 3,200 ppm |
| Some models | 3,000 to 3,500 ppm | 3,200 to 3,400 ppm |
| Low-salt systems | 1,000 to 1,500 ppm | as specified |
Always follow the manual for your cell. Too little salt and the generator stops making chlorine; too much and it may shut down and the water can taste salty and corrode metal fittings.
How to add salt
- Test the salt level with test strips or a digital meter, not just the generator’s display, which can drift.
- Turn the generator off, but keep the pump running.
- Pour the salt around the shallow end, away from the skimmer, and brush it toward the main drain.
- Wait 24 hours for the salt to dissolve completely, then test again before switching the cell back on.
Which salt?
Use pool salt that is at least 99% pure sodium chloride, without anti-caking agents or iodine. Water softener pellets dissolve slowly, and rock salt carries impurities that can stain the pool.
Salt is not lost through evaporation, only through splash-out, backwashing and rain overflow, so after the first fill you only top up small amounts each season.