“This pump will handle your whole system” is not a sizing method. Irrigation pump selection depends on the gap between available source flow and the demand of the sprinklers, expressed through flow rate and total dynamic head rather than horsepower alone.
An undersized pump leaves rotors dribbling, while an oversized pump can create water hammer and damage pipe joints. Both failures come from selecting equipment without matching the pump curve to the system’s actual demand.
A correctly matched pump can run reliably for a full season. The way out of guesswork is to measure source flow, calculate total dynamic head, and select a pump curve that meets both at an efficient operating point.
This guide covers pump types, the sizing math, and the specifications needed to avoid expensive mismatches. The focus is on usable measurements and pump-curve decisions rather than a generic horsepower recommendation.
What size pump do I need for my irrigation system?
Calculate total flow (GPM) and total dynamic head (TDH), then pick a pump whose performance curve has your GPM × TDH intersection in the efficiency zone. Skip the guesswork: add up your sprinkler nozzles’ GPM ratings, measure your well’s static water level and drawdown, and compute TDH = vertical lift + friction loss + operating pressure. 5 HP pump — but your numbers will differ, and guessing costs real money.
Here’s the breakdown that saved me from buying a fourth pump.
