Irrigation Professionals with questions about ... - Hunter Industries

5. Multiply your answer by the length of pipe supplying thissprinkler only (just to the next head on the zone).6. Write this number down.On the plan, note the GPM requirement for the next to the last head on thezone which you have chosen to calculate. Add the two GPM rates together(the last head and the next to the last head). This number is the amount ofwater that will flow through the next length of pipe. Repeat steps 1 - 6 tocalculate the friction loss for this section of pipe.Repeat this process for all lengths of pipe on the zone back to the valve.Losses Through Main Line PipeContinuing toward the POC, use the total GPM for the zone, and calculatethe friction losses in the main line. Don’t forget, you may have changedthe type of pipe for the main line, so use the appropriate friction loss chart.Friction Losses for FittingsThe friction losses for couplings, elbows, and tees can be high. Use thechart on page 10, in the Hunter Friction Loss Tables to figure the losses.An acceptable pressure loss figure to use if you don’t want to calculateeach fitting is 10% of the losses established for the pipe. It isrecommended that you calculate several systems first to see if a 10%figure is accurate to your designs.Losses Through Valves and Other ComponentsSee the manufacturer’s catalog for the friction loss through valves andother components: control valves isolation valves backflow preventer pressure regulator filterTotal System LossesAdd the friction losses for all of the pipe and other components all the wayback to the irrigation POC. Remember to include pressure losses forelevation gain from the highest head in the system to the POC (or pressuregains for heads which are lower than the POC).Refer back to the original calculation for design capacity and dynamicpressure. Make sure the system requirements that you just added up arewithin the calculated design capacity. Subtract the system’s friction loss