Irrigation Professionals with questions about ... - Hunter Industries

100 ft.75 ft.Point A100 ft.Point B1-1/4 in. CL 200 PVC85 psi at Point A18 GPM50 ft.Elevation ViewFigure 20In Figure 20, all the pipe is 1-1/4-in. Class 200 PVC and the flow is18 GPM from point A to point B. At point A, a pressure gauge readingindicates 85 PSI. In order to determine the dynamic pressure at point B,first find the pressure change due to change in elevation and then combinethat with the friction loss in the pipe.Pressure loss due to the higher elevation at point B (an elevation gain):75 ft. x 0.433 PSI per ft. of elevation change = 32.48 PSI less atpoint BPressure loss due to friction in the pipe:Use the friction loss charts at the back of this manual to find thepressure loss at 18 GPM in 1-1/4-in. Class 200 PVC pipe: frictionloss from the chart is 1.24 PSI per 100 ft.PSI loss in pipe:(50 ft. + 100 ft. + 100 ft.) x (1.24 PSI loss per 100 ft. ÷ 100 ft.) = PSI lossNote: the 1.24 PSI loss from the charts is PSI loss per 100 ft. and isdivided by 100 to find the pressure loss per foot,(1.24 ÷ 100 = 0.0124).so, the PSI loss in pipe = 250 ft. x 0.0124 PSI loss per ft.PSI loss in pipe = 3.10 PSI [total due to friction loss]85.00 PSI pressure at point A- 32.48 PSI due to elevation change52.52 PSI subtotal at point B- 3.10 PSI due to friction loss in pipe from point A topoint B49.42 PSI dynamic pressure at point B