Pressure Tank vs. Well Pump: How to Tell the Difference

Why They Look So Similar

Both a failing pump and a failing pressure tank can produce low pressure, pressure that surges and drops, and a pump that seems to run "too much." The pressure tank's job is to let the pump rest between short bursts of demand — when the tank fails, the pump has to work far harder and far more often, which can look and sound like the pump itself is the problem.

Signs That Point to the Tank

• Pump cycles on and off rapidly — every few seconds — rather than running in longer, spaced intervals
• Tapping the tank produces a solid (not hollow) sound most of the way up, suggesting it's waterlogged
• The tank feels unusually heavy for its size, or you can hear water sloshing when you nudge it
• Pressure gauge near the tank swings quickly between cut-in and cut-out pressure rather than holding steady

Signs That Point to the Pump

• Pump runs continuously and never reaches cut-out pressure at all, even after the tank has been checked
• Motor hums but doesn't run, or trips the breaker on start-up
• Sediment or sand appears in the water along with reduced flow
• Pressure tank tests fine (correct air charge, no waterlogging) but symptoms persist

The Quick Field Test

With the system depressurized, check the tank's air pre-charge at the Schrader valve — it should read about 2 psi below the pump's cut-in pressure (commonly around 38 psi on a 40/60 system). A reading at or near zero, or water coming out of the valve, confirms tank failure. If the tank charge checks out and problems continue, the pump, pressure switch, or wiring is the more likely culprit.

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