The short answer
Hard water between regenerations after the valve, salt and settings check out is the main sign; resin beads at the taps point to a broken riser or distributor.
Rule out the rest
- Salt present, no bridge.
- Hardness set to your water plus iron.
- Bypass in service.
- Valve seals and piston sound.
Resin signs
- Capacity keeps shrinking: hard water returns sooner each week.
- Iron staining on the resin bed on iron-bearing water.
- Resin beads in faucet aerators (a broken distributor).
Replacing it
Buy the volume your tank holds (resin calculator): AFWFilters SOFRES1 1 cu ft Softener Resin, iFilters MED-CAT-025 1/2 cu ft Softener Resin.
Products mentioned
Questions readers ask
How long does water softener resin last?
It varies with chlorine and iron in the water; shrinking capacity is the practical sign.
Can I clean resin instead of replacing it?
Resin cleaners exist for iron fouling; worn resin still needs replacing.