A softener is a small number of parts and most faults come from a short list of them. Knowing which component produces which symptom turns a service call into a part order, and knowing which failures are worth repairing on an older unit stops good money going into a machine that has reached the end of its life.
The injector, the most common fault
The valve draws brine using a venturi injector, and that injector has a small orifice and a fine screen that catch salt fines, rust flakes and grit. When they block, the brine draw fails, the resin never recharges, and the household gets hard water while the salt level stops falling. It is the first thing to check on any softener that has stopped softening. Pull the injector cap, rinse the nozzle and screen clean rather than poking at the orifice, and refit. It is a cheap part and a common one to keep spare.
Seals, spacers and the piston
Inside the control valve a piston moves through a stack of seals and spacers to direct water through each stage of the cycle. Those seals harden and wear, and the symptoms are water running continuously to drain, a cycle that will not advance, or hard water passing during service. Seal and spacer kits are sold for most valves and replacing one is a methodical job rather than a difficult one, provided the parts go back in the correct order. On a valve that has already been rebuilt once, a new head is often the better spend.
The brine well, float and safety valve
The float in the brine well limits how much water enters the tank, and a float stuck high or an overflow valve that has failed produces a tank filling with water and, eventually, an overflow. A float stuck low starves the brine draw. Both are inexpensive parts. This is also where a salt bridge does its damage: a crust spanning the tank leaves the brine well drawing from a nearly empty space while the tank looks full, which mimics an injector fault exactly.
Resin and the distributor, the ones that end a unit
Resin lasts many years unless fouled by iron or degraded by chlorine, and replacing a bed is a media job rather than a part swap. A cracked riser tube or a broken lower distributor sends resin into the household plumbing and means stripping the tank. Both are the point at which the age of the unit matters: on an old softener with a worn valve as well, replacement is usually the better decision. Our softener installation guide covers what a new unit involves.
Questions people ask about water softener components
My softener has stopped using salt. What do I check first?
The injector and its screen, then whether a salt bridge has formed. Both stop the brine draw while the tank still looks full.
Water is running to drain continuously. Which part?
Usually the control valve's piston and seal stack, which directs flow through each stage. Seal kits are available for most valves.
Is it worth rebuilding an old valve?
Once, generally yes. On a valve already rebuilt, or alongside fouled resin, a new head or a new unit is usually the better spend.
There are resin beads in my taps. What happened?
A cracked riser tube or a failed lower distributor. That means stripping the tank, and on an older unit it often decides replacement.