How much salt a saltwater pool needs
How salt chlorine generators use salinity, what target ppm to aim for, and how to dose a new fill or top up an existing pool without overshooting.
Why a salt pool needs salt at all
A saltwater pool is still a chlorine pool. The salt cell passes water over electrified plates and splits dissolved sodium chloride into chlorine, which sanitizes the water before recombining back into salt. That cycle means the salt is not consumed the way chlorine tablets are, so once you reach the target salinity you mostly top up for losses from splash-out, backwashing, and rain dilution rather than dosing constantly.
Picking the right target
Generators specify an operating salinity, commonly near 3,200 ppm, within a broader band of roughly 2,700 to 3,400 ppm. Below the low end the cell cannot make enough chlorine and may flash a low-salt warning, while well above the high end you risk scaling and corrosion of metal fittings. Enter your generator's exact target rather than a generic number, because a few hundred ppm either way changes both performance and the amount of salt this tool recommends.
Dosing a new fill versus a top up
On a fresh fill the current salinity is essentially zero, so the tool asks for the full jump to target, which for a 20,000 gallon pool at 3,000 ppm works out to about 500 pounds. On an established pool you enter the reading from your strip or meter, and the tool only doses the gap. Adding salt in stages and retesting after the water has circulated is the safest way to land on target, since removing excess salt means draining and refilling.
Getting an accurate volume
The single biggest source of error is the pool volume, because the salt weight scales directly with gallons. An estimate that is 20 percent high leads to salt that is 20 percent high, and that overshoot can be tedious to correct. If you are unsure of your volume, measure it from the pool dimensions or a filling record before trusting any salt dose.