Pump Won't Prime
A pump that can't draw water up from the source (won't prime) has an air leak on the suction side, a failed foot valve, or the suction lift is too high.
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Symptoms
- You fill the pump with water but it won't draw from the well/pond
- Air keeps coming into the pump volute
- Pump runs dry and overheats
Diagnosis
Air is entering the suction line faster than the pump can purge it, preventing the pump from creating enough vacuum to draw water.
Step-by-Step Repair
- 1
Turn off the pump. Fill the pump volute and suction pipe completely with water through the priming port.
- 2
Start the pump. If it briefly pressurizes then loses prime, you have a suction-side air leak.
- 3
Inspect every fitting, joint, and connection on the suction pipe from the pump back to the water source. Tighten all connections.
- 4
Check the foot valve at the water source. A stuck-open foot valve lets water drain back. Replace if the flapper doesn't seal.
- 5
Verify the suction lift (vertical distance from water level to pump) doesn't exceed 25 feet. Centrifugal pumps can't reliably lift more than this.
- 6
Apply soapy water around suction-side fittings while the pump runs. Bubbles indicate an air leak at that joint.
Pro Tips
- Thread sealant (pipe dope) works better than Teflon tape for suction-side threaded connections because it fills gaps more completely.
Prevention Tips
- Install a check valve close to the pump to help maintain prime. Foot valves alone aren't always enough.
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