Irrigation Pump & Pipe Sizing Calculator

How It Works

1. Enter Flow Requirements

   Input target flow rate (GPM) and select pipe material (PVC, aluminum, HDPE, steel new, steel aged) and pipe size.

2. Enter System Details

   Input total pipe length, elevation change, delivery pressure, suction head, and add any fittings (elbows, tees, valves) for equivalent length calculation.

3. Review Pump Sizing

   See total dynamic head (TDH), required pump HP, velocity check, and energy cost estimates. Use the pipe comparison table to evaluate alternative sizes.

Built For

• Farmers sizing new irrigation systems
• Irrigation dealers designing systems for customers
• Well drillers recommending pump sizes
• Farm managers evaluating irrigation energy costs

Assumptions

• Friction loss uses the Hazen-Williams equation with published C-factors for each pipe material (PVC=150, aluminum=130, steel new=140, steel aged=100, HDPE=150)
• Fitting equivalent lengths follow standard hydraulic references and are added to straight pipe length for total equivalent length
• Pump efficiency is user-entered or defaults to 70%, representing a typical centrifugal irrigation pump
• Water temperature is assumed at 60-70 degrees F; viscosity changes at extreme temperatures are not modeled
• Suction head assumes a stable water source (well or reservoir) with no drawdown during pumping
• Energy cost assumes constant electric rate or fuel price over the operating period

Limitations

• Hazen-Williams is empirical and only valid for water near 60 degrees F in turbulent flow — not applicable to other fluids or laminar flow conditions
• C-factor degrades over time with corrosion, scale buildup, and biological fouling — aged pipe may have C values 20-40% lower than new pipe
• Does not model transient conditions (water hammer) that occur during pump start/stop or valve operation
• Velocity recommendations (5 ft/s PVC, 7 ft/s steel) are guidelines — actual surge limits depend on pipe class and fittings
• Does not account for well drawdown, which increases suction lift as pumping continues
• Not applicable to drip irrigation systems where emitter flow characteristics and pressure compensation dominate the design
• Does not size check valves, pressure relief valves, or surge protection devices

References

• ASABE EP405.1 — Design and Installation of Microirrigation Systems (pipe sizing methodology)
• USDA-NRCS National Engineering Handbook Part 623 — Irrigation (Chapter 8: Pumping Plant Design)
• Hydraulic Institute Standards — Centrifugal Pump Application Guidelines
• Irrigation Association — Landscape Irrigation Auditor Handbook (Hazen-Williams reference tables)
• University of Nebraska Extension EC 701 — Pumping Plant Performance and Irrigation Energy Costs
• Rain Bird / Toro / Lindsay — Irrigation system design manuals (friction loss charts and velocity limits)

Frequently Asked Questions