A pump that runs but never builds pressure has one of 7 problems. Here is how to find which one — starting with the easiest checks.
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Check the pressure gauge while the pump runs. If the needle doesn't move at all, the pump may be running dry (no water), or the gauge itself may be faulty. If pressure rises slightly but never reaches cut-off, the pump is running but can't keep up with demand.
A failed check valve lets pressurized water drain back into the well the moment the pump stops. The pump must re-pressurize from zero every cycle and may never reach cut-off pressure. Listen for a gurgling sound after the pump stops.
A completely waterlogged tank provides zero storage — the pump runs continuously fighting to maintain pressure it can never hold. Test the Schrader valve.
The pump is pulling air instead of water. Pressure gauge barely moves. Pump trips on thermal overload after running. Let the well recover for 30–60 minutes and test again. For general guidance on maintaining your private well system, see the EPA's private wells overview.
If cut-off is set above the pump's maximum shut-off pressure, the pump runs forever trying to hit a target it cannot reach. Check the switch setting against the pump's rated pressure.
Any air entering the suction pipe on a jet pump breaks the vacuum needed to lift water. Even a small crack at a fitting can prevent pressure from building.
Worn impellers move less water per revolution. Pressure builds slowly or plateaus well below cut-off. More common in pumps over 10 years old or those that have pumped sand.
Sometimes the simplest explanation — the gauge is stuck or faulty. Check water flow at a faucet. If water flows normally, the gauge is the problem, not the pump.
This almost always points to either a failed check valve letting water drain back into the well between cycles, a waterlogged pressure tank with no storage capacity, or a pressure switch cut-off set higher than the pump can physically reach. Testing the Schrader valve and listening for gurgling after shutoff are the fastest first checks.
On some jet pumps, yes — the impeller is a separate serviceable part. On submersible pumps, the impeller stack is generally not a practical field repair, and by the time the pump is pulled from the well, replacing the whole unit is usually the better value.
If pressure barely rises, the pump trips on thermal overload after running, and the well has been used heavily just before the problem started, a low water table or slow-recovering well is a likely cause. Letting the well sit for 30-60 minutes and retesting will usually confirm this — a pump problem won't improve just from waiting.
Turn it off if you suspect low well water, since running a pump dry can burn out the motor within minutes. For other causes like a bad check valve or pressure switch, short test runs to observe gauge behavior are fine, but don't leave it running unattended while diagnosing.
An undersized tank causes low pressure, short cycling, and early pump failure. Check yours free in 2 minutes.
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