Pump Runs But No Pressure
If the pump motor is running but you have little or no water pressure, the pump has likely lost its prime, the impeller is damaged, or there's a suction-side leak.
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Symptoms
- Pump motor runs but pressure gauge reads zero or very low
- Little to no water comes out of sprinkler heads
- Pump sounds different than normal (higher pitched, cavitating)
Diagnosis
The most common cause is loss of prime (air in the suction line). Other causes include a worn impeller, clogged suction strainer, or a leak on the suction side allowing air intrusion.
Step-by-Step Repair
- 1
Turn off the pump. Check the suction-side piping for any visible air leaks (loose fittings, cracked pipe).
- 2
Check the priming plug on the pump volute. Open it and fill the pump housing completely with water to re-prime.
- 3
Check the foot valve (at the bottom of the suction pipe in the well or pond). A failed foot valve lets water drain back and the pump loses prime.
- 4
Inspect the suction strainer/screen for clogs — debris buildup reduces flow dramatically.
- 5
If the pump primes but pressure is still low, the impeller may be worn. This requires pump disassembly or professional service.
Pro Tips
- Suction-side air leaks are the most common cause of lost prime. Even a tiny crack will let air in.
Prevention Tips
- Install a check valve on the suction line close to the pump to help maintain prime between cycles.
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