Salt

Adding salt

1 lb per 1,000 gallons raises salt 120 ppm. Bags are 40 lb, so one bag moves a 15,000-gallon pool 320 ppm.

The controller's own salt reading drifts as the cell ages and reads low on a worn cell. Trust your test, not the display. A controller reading well below your test result is a sign the cell is near the end.

Only test this on a pool with a salt chlorine generator. On any other pool the field stays blank.

A salt cell makes chlorine by running current through salty water. Too little salt and it can't produce. Too much and you're wasting salt and pushing up TDS for nothing.

Check the cell, not a chart

Manufacturers specify different ranges and they're the ones who warranty the cell. The range is printed on the cell or in the controller menu. Use that number.

Low salt is the expensive failure

Running a cell below its range makes it work harder for less chlorine, and it shortens cell life. Cells are a few hundred dollars. A bag of salt is under ten. Topping up early is the cheap decision.

Salt doesn't evaporate. It leaves through splash-out, backwashing, and rain overflow, and it gets diluted by every refill. A pool that drops steadily every week has a leak somewhere, not a salt problem.

Salt and the rest of the water

Salt pools drift up on pH because making chlorine raises it, so you'll run acid more often. They also carry 3,000-plus ppm of TDS by design, which is normal and not a reason to drain. See total dissolved solids.