On pools with cartridge filters or pools with a booster pump running the cleaning system you may need to clean the module in the water valve periodically. To do this turn off the pool pumps.  Remove the clamp and lid of the water valve and then remove the module in the valve base.  Note; on a system with more than one water valve one of the modules will be special and have a bridge(s) onthe top of the module, this must be replaced in the same base in the same exact orientation.  Put the module in the pool water sideways and swish it back and forth fast about 5 times.  Turn it upside down and push (never rotate) the any protruding pistons back against the bottom plate.   Spin the gear closest to the center pin on the top of the module to confirm rotation and gear mesh. Replace the module into the base.  Clean the O-ring and lid and replace it and the clamp.  Note: While tightening the nut on the band clamp you must tap on the clamp as you tighten the nut starting on the opposite side from the nut.  This will allow the clamp to draw up evenly. Sometimes the O-ring will swell larger than the groove and will not fit. You must replace a swollen O-ring.