Designing an Irrigation System: Flow, Pressure, and Pipe Sizing

Critical Factors for a Functional Design

A user wants to design a system for a neighbor using a 1-inch or 1.25-inch pump discharge, with a 3/4-inch flexible tubing tap 25 feet from the pump, then 100-foot zone runs.

Key Advice

• Backflow prevention is essential when tapping into domestic water.
• Demand (GPM) matters more than PSI. With 8 GPM available, keep each zone under 7 GPM.
• Use larger pipe (1-inch) throughout to minimize friction loss.
• Pressure regulator may be needed if supply pressure fluctuates widely.

Simplified Bucket Test

The bucket test at a faucet near the pump is acceptable for estimating flow; the elaborate procedure is for high-precision design.