A bum water softener control valve can cause the unit to leak or stop producing soft water. A leak automatically means a rebuild, but if you've run out of soft water, first check the power at the receptacle. If the receptacle works and your softener is more than five years old, chances are good that you're due for a control valve rebuild. Water softener repair pros charge about $200 to do that. But you can do it yourself in about an hour and for less than $60. I'll show you how to rebuild one of the most common valves (the Fleck 5600 series) and direct you to a Web site for rebuild instructions for other brands.
It'll take some detective work to find the make and model of your control valve because they don't have identifying labels. So take a photo of your valve and go to softenerparts.com. Click on “I.D. Your Control Valve” and match your photo to the valves there. If you have a Fleck control valve, buy a complete rebuild kit and follow the instructions here. If you have a different brand, locate the parts and rebuild instructions on the site's menu.
Start the rebuild by relieving the internal water pressure. Turn the bypass valve to the “bypass” position and rotate the dial to the “backwash” position. Unplug the power cord. Then remove the back cover, the housing screws and the screw in the center of the main piston. Tilt the housing and lift it off. Remove the hold-down plate screws and the plate. Then grab the piston and pull it straight up (Photo 1). Next, remove the spacers and seals (Photo 2).
Remove the old brine valve and install the new one (Photo 3). Then install the new seals and spacers (Photo 4). Insert the new piston and install the hold-down plate. Reinstall the housing, turn on the water and check for leaks. Then turn the dial to put the unit into a manual regeneration and check again for leaks.