Diagnosing Fluctuating Pressure in a Deep Well Irrigation Pump

Why Your Irrigation Pump Pressure Swings from 80 PSI to 45 PSI

A homeowner with a pump set at 400 ft depth and a water table 200 ft above the pump sees pressure fluctuate wildly—80 PSI one day, 45–60 PSI the next. The well depth and water table appear stable.

Likely Causes of Pressure Fluctuation

• Pressure tank issues – A waterlogged or failed bladder tank causes rapid cycling and pressure swings.
• Pressure switch malfunction – Worn contacts or incorrect settings lead to erratic cut-in/cut-out pressures.
• Partial blockage in the line – Sediment, mineral buildup, or a partially closed valve restricts flow intermittently.
• Pump wear – Impeller damage or seal failure reduces efficiency unpredictably.

Recommended Action

Since the water table is stable, focus on the above-ground components. Inspect the pressure tank (check air charge), test the pressure switch, and examine the discharge line for obstructions. A well service technician can diagnose and repair these issues efficiently.