Pipe Sizing Calculator

Overview

Maps design flow to a nominal pipe-size tier, estimates a simplified pressure loss from run distance, and adds pipe and fitting quantities.

Assumptions

• Sizing thresholds are simplified and pressure loss is a planning estimate.
• The 10% pipe allowance is for cuts.

Worked example

At 10 GPM the tool selects 1-in pipe. For a 100-ft run, estimated loss is 100 ÷ 100 × (3.5 ÷ 1) = 3.5 PSI.

Common mistakes

• Using static pressure as available operating pressure.
• Ignoring elevation, fittings, backflow devices, and manufacturer friction charts.

Limitations

It is not a complete hydraulic design and does not determine potable-water code compliance.

Safety and local requirements

Shut off water before work and check local plumbing, backflow, and irrigation requirements.

Sources

• EPA WaterSense — irrigation efficiency background