Calculating GPM for Sprinkler System Design

Step-by-Step GPM Determination for Irrigation Design

Beginner wants easiest way to figure GPM for any system.

Static pressure at water source.
Pressure loss from source to point of connection (POC).
Layout on paper – Calculate friction loss to farthest head in farthest zone.
Determine available GPM at minimum 35 PSI at that farthest head.
Size pipe critically—undersized pipe kills pressure.

Use friction loss charts (PVC, poly) for each pipe segment. Software helps, but manual calc teaches the fundamentals.

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