20mm 3/4" Non Return Isolation Pressure Reduction Valve AVG NRI-PRV-20C can be a valuable addition to many piping systems. If the incoming water pressure is too high, this can put unnecessary strain on water heaters, pipe work, plumbing joints, taps and tap washers. It can increase the risk of burst hoses on washing machines, water leaks and possibly magnify any existing water hammer problems. The AVG non return isolation pressure reduction valves (NRI-PRV) are factory set at 500 kPa. The downstream pressure is adjustable from 250 to 650 kPa. For pressure monitoring, there is a gauge port on the body of the valve so that a gauge can be fitted to monitor the upstream and downstream pressure.