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How To Calculate Slope & Determine Zones Needed

By using the diagrams below, you can accurately measure a slope and calculate how many zones you’ll need to install your irrigation system.ย  Sprinkler Warehouse recommends that you download these helpful worksheets & the irrigation equations to follow these charts step by step.
Determine the Percentage of Slope
Divide the measure of height by the measure of the length and multiply by 100.

Example Above: 2 Divided By 14 Times 100 = 14.3%

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Irrigation
Checklist
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Timer to Valve Wire Sizing Chart
GaugeMaximum Distance
181000 ft
141450 ft
101750 ft
101750 ft
Valve Inlet Size
Size of InletGallons Per Minute (GPM)
3/4″> 0-10
1″> 10-20
1 1/2″> 20-30
2″> 30-150
PVC Pipe / Schedule 40PVC Pipe / Class 200
Max GPM FlowPipe SizeValve SizeMax GPM FlowPipe SizeValve Size
> 0-41/2″1/2″> 0-61/2″3/4″
> 4-83/4″3/4″> 6-103/4″3/4″
> 8-121″1″> 10-161″1″
> 12-221 1/4″1″> 16-261 1/4″1″
> 22-301 1/2″1 1/2″> 26-351 1/2″1 1/2″
> 30-502″2″> 35-552″2″

Use this chart to size your pipe according to GPM needed for each zone.

PVC Pipe / Class 125Poly Pipe / Galvanized Pipe
Max GPM FlowPipe SizeValve SizeMax GPM FlowPipe SizeValve Size
> 0-41/2″1/2″
>0-103/4″3/4″> 4-83/4″3/4″
>10-151″1″> 8-121″1″
>15-241 1/4″1″>12-221 1/4″1 1/4″
> 22-301 1/2″1 1/2″
> 35-502″2″

Use this chart to size your pipe according to GPM needed for each zone.

Flow Rates for Service Lines
Length of String2 3/4″2 1/4″3 1/2″4″4 3/8″5″
Size of Copper3/4″1″1 1/4″
Size of Galvanized3/4″1″1 1/4″
Size of PVC3/4″1″1 1/4″

Determining The Amount Of Zones

Product Performance Charts

Use this article in addition to the Basic Steps Irrigation Installation Checklist.

Pictured above are helpful worksheets & irrigation equations.