Pipes & water supply

Well pump loses prime

A pump that loses prime stops moving water even though it's running, usually due to air entering the system through a leak or a failed check valve.

Difficulty
Advanced
Time
30–60 minutes
DIY cost
$20–$60
Pro cost
$300–$1000+

Symptoms

  • Pump runs but no water comes out of fixtures
  • Sputtering or air in the water when it does come out
  • Pump seems to run longer than usual before pressure builds
  • Problem recurs after any period of pump being off

Likely causes

  • CommonFailed foot valve or check valve allowing water to drain back down the wellThis valve is supposed to hold water in the pipe when the pump stops, and if it fails, the pipe drains and the pump loses its prime.
  • CommonAir leak in the suction line (for jet pumps)A loose fitting or crack on the intake side lets air in instead of pulling water, preventing the pump from priming.
  • PossibleWell water level dropped below the pump intakeDuring drought or heavy usage, the water table can drop temporarily below where the pump can draw from.
  • Less commonWorn pump impeller or sealsInternal wear can prevent the pump from building enough suction to prime properly even with no leaks.

What to do

  1. Turn off the pump and check all visible suction-side fittings for looseness or cracking, tightening or resealing as needed.
  2. For a jet pump, most manufacturers require manually priming the pump by filling the pump housing and suction line with water before restarting.
  3. Locate the priming plug on top of the pump, remove it, and fill the housing with clean water until full.
  4. Replace the plug and turn the pump on briefly to check for pressure building; repeat priming if needed.
  5. If the pump loses prime again shortly after, suspect the foot valve or check valve at the bottom of the well pipe, which usually requires pulling the pipe to replace.
  6. Check the well's static water level if you suspect a low water table, which may require a well log or professional water level test.
  7. Persistent prime loss despite a good check valve and no leaks suggests worn pump internals needing professional service.

Tools and parts

  • Wrench
  • Water for priming
Foot valve or check valve for well pumpSearch: “well pump foot valve check valve”

When to call a pro

Call a well contractor if priming doesn't hold, since pulling the drop pipe to replace the foot valve requires specialized equipment.

Safety

Generally low risk

Generally low risk for a careful person. Stop if anything looks different from what this guide describes.

Related guides

Operator provides AI-generated troubleshooting information. It can be wrong. For safety-critical, electrical, gas, structural, medical, automotive safety, or other high-risk problems, consult a qualified professional.