Oklahoma Irrigation Pumps: Why and How to Test Efficiency per OSU Extension

OSU Extension fact sheet BAE-1525, "Irrigation Pump System Testing" (March 2017, Robert Scott Frazier and Carol Jones). Only stated points are included; the page's dollar example is left out.

Key points from the page

In heavily irrigated areas, in some locations with heavy irrigation operations, pumping systems can make up the majority of energy costs. Older systems are rarely near optimal efficiency: impellers corrode, wear and break, pipes clog with sediment and mineral buildup, and impellers are often mismatched to motor power or desired flow.
The system curve (flow vs head) and the pump performance curve intersect at the operating point. Best design practice prefers it close to the best efficiency point (BEP).
Formulas given: hydraulic horsepower HPw = TDH x GPM / 3,960; total efficiency = HPw x 0.746 / measured kW.
Total dynamic head is described as one of the most difficult parameters to measure; pressure requirements are often overestimated.
Flow can be measured with clamp-on ultrasonic devices or in-line meters.
Benchmarks: above 60% is called excellent condition; 49% or below signals poor design, poor condition, or both, and the system needs repair or replacement. Typical total efficiency is 40% to 70%.
The authors recommend testing pumps every three to five years.
Testing difficulties: inaccessible well openings (water level guessed), air or solids disturbing flow readings, and non-constant loads.
Operations with several large pumps and long hours may benefit from professional testing, often offered by irrigation, drilling and pump supply companies.

Not verified: Oklahoma water rights, well permits and any site-specific sizing; the table of efficiency ranges by horsepower was not reproduced here beyond what the page states.

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General information only. Not plumbing, legal or code advice. Confirm with a licensed professional and your local authority.