Salt Dose per Regeneration

The salt setting is the single most consequential number in a softener's programming, and it is a straight multiplication: dosage per cubic foot times cubic feet of resin. Two cubic feet at 8 lb/ft³ draws 16 lb of salt per regeneration. What makes the choice interesting is that capacity and salt efficiency pull in opposite directions. At 6 lb/ft³ you get about 20,000 grains per cubic foot — roughly 3,300 grains per pound of salt, excellent efficiency. Push to 15 lb/ft³ and capacity climbs to about 32,000 grains, but efficiency collapses to around 2,100 grains per pound. You buy the last third of the capacity at nearly double the salt cost.

That trade-off drives real regulation. Several US states and California in particular set minimum salt efficiency standards, and high-efficiency programming means running low salt doses with proportionally more frequent regenerations. The counter-argument is hardness leakage: a lightly regenerated bed keeps more residual calcium on the bottom of the column and leaks 1–3% of inlet hardness into service, which matters if the softener is feeding a boiler or an RO. Field practice on a well with 25 gpg and an RO downstream is to run 10–12 lb/ft³ and accept the salt; on a municipal supply at 8 gpg feeding a house, 6 lb/ft³ is plenty. Also confirm the brine tank actually makes saturated brine — a bridged salt crust means the valve draws water, not brine, and the bed never regenerates at all.