If your water softener tank isn't working because of salt deposits in the tank, you can remedy this by cleaning the tank. There's an air pocket trapped underneath the salt deposits -- if you remove the deposits, air can flow through the tank and soften the water. Break up salt deposits with a broomstick and remove the salt from the tank. Vacuum the sediment out of the tank and wash out the whole tank with warm, soapy water.
The resin bed may eventually develop a problem if your tank is removing iron from your hard water. Iron can clog the resin bed, preventing the tank from working correctly. Use a resin cleaner, such as Iron Out, or use citric acid or bleach to clean out the resin bed. Add the cleaner to the tank then remove the cover from the control valve to access the regeneration knob. Press this knob in with a flat head screwdriver to start the regeneration cycle.
A clogged injector can also cause the water softener resin tank to stop working properly. Salt can turn to sediment in the tank and clog the injector. To repair it, shut the water off to the tank by turning the bypass valve. Run the regeneration cycle to relieve the water pressure in the tank. Remove the caps from the softener head and clean both sides of the head -- the injector and the screen -- before putting the softener head back together and turning the water back on.
If the resins inside your tank are old, you will need to replace them. Turn off the water and unplug the tank. Disconnect the control valve from your water line, drain line and brine line, as well as from the tank. Dump the water and resins out of the tank or vacuum them out. Clean the tank with bleach and a toilet brush. Pour new resins into the tank through a funnel. Put the tank back together, reconnect it to all of the lines then turn the water back on. Run the regeneration cycle. When the cycle's done, run the water from your home into the tank for a few minutes to clear out any trapped air.