How Often Should a Water Softener Regenerate? Days and Gallons

The short answer

Regeneration interval = usable capacity ÷ grains used a day. Penn State Extension's example: four people × 75 gallons × 10 gpg = 3,000 grains a day; a 20,000-grain unit regenerates about every six to seven days. About weekly is the usual target. A metered valve counts gallons and regenerates when the capacity is used; a timer regenerates on a schedule whether it's needed or not.

Timer vs metered

Regeneration control
	Timer	Metered (demand)
Triggers on	Days	Gallons used
Salt use when water use varies	Higher	Lower
Setup	Days between regenerations	Hardness and capacity

Signs it's not regenerating right

Hard water returns before the next regeneration: capacity too small, wrong hardness setting, or worn resin.
Salt level never drops: a bridge in the brine tank or a brine-draw problem.
Water stays high in the brine tank: see why a brine tank fills with water.

Setting it

Enter your hardness (plus about 4 gpg per ppm of iron) on a metered valve. On a timer, set days from your usable capacity and load; the sizing calculator shows both.