Irrigation Professionals with questions about ... - Hunter Industries

Backflow Preventer and Valve SizingBackflow preventers and automatic control valves can be large pressureconsumers. Sizing these valves is easy – simply use the manufacturer’spressure loss charts. Isolation valves can be great tools if valvemaintenance is necessary, and are mandatory for winterization if thesystem is installed in freezing climates.Backflow PreventersBackflow preventers are generally sized the same size as, or one sizesmaller than the mainline. Check the pressure loss chart in themanufacturer’s product catalog to be sure it is not sized too small. Usecaution when sizing backflow preventers. If they are sized too small, highfriction losses may occur.Isolation Valve SizingIsolation valves (gate valves or ball valves) should be line size. In otherwords, if the main line is 1”, the isolation valve should be 1”; if the mainline is 1-1/4”, the isolation valve should be 1-1/4”.Automatic Zone Control Valve SizingSize automatic control valves according to the zone flow raterequirements. Generally speaking, automatic control valves can be sizedas small as one size smaller than the lateral line it is serving. Check thepressure loss chart in the product catalog to be sure it is not sized toosmall. Use caution when sizing control valves. If the valves are sized toosmall, high friction losses are inevitable, and water hammer is likely.