The short answer
About once a week is the usual target; size the softener or set the timer so it runs about seven days on your load.
The target
Penn State's worked example lands on about six to seven days. Much shorter wastes salt and water; much longer on a timer means regenerating before it's needed.
Your interval
Usable capacity ÷ grains a day. Work it out with the regeneration calculator.
Changing it
- Too short: a larger unit or a lower (correct) hardness setting.
- On a timer: set the days to match your load.
- Metered valves set themselves from capacity and hardness.
Products mentioned
Questions readers ask
How many days between softener regenerations is normal?
About seven is a common target.
Is it bad if my softener regenerates every day?
It uses more salt and water than needed; check sizing and settings.