First thing to check is the nozzle and venturi for obstructions and if the venturi gasket looks degraded replace it. It is in the grey housing attached to the main control valve. Also check the refill flow control button in the venturi housing. If all that is clear, you will probably have to replace the rotor/disc and seal kit in the main control valve as it may be worn and allowing water to bypass the proper channells. These are the two most common problems to allow water to build up in the brine tank on a Sears softener.