I have an Kenmore water softener that's at least 8 years old. It's been working fine until a couple of weeks ago. Water was hard and I noticed that the brine tank was half full of water. I found some instructions and videos on cleaning the softener, specifically the venturi as well as other screens. They were pretty gummed up but are all clean now. Nothing seems blocked and taking the unit apart, everything seems open and water flows through all valves and such. It all worked ok for about two weeks, then the water started getting hard again and the tank was filling with water again. I checked again the venturi, all seals and o-rings, all the valves and seals, discharge screen and the brine tank line and valves. All cleat and working. The mechanism motor works fine and the gears and main valve seem to operate fine. I'm at a loss to figure out what is going on. Any suggestions or recommendations?