How to Prime a Well Pump

Before you start: is it really lost prime?

A jet pump that has lost prime runs, often with a hum or a rising whine, but the pressure gauge barely moves and little water reaches the taps. Goulds lists "pump not primed," an air leak in the suction pipe, and too little submergence of the suction pipe as causes of little or no water.

If the motor doesn't run at all, priming won't help. Check the breaker and the pressure switch first. Our jet pump problems page sorts out which is which.

Tools and supplies

• A few gallons of clean drinking water in buckets or jugs. It goes straight into your water system, so don't use pond or rain barrel water.
• A funnel that fits the priming port.
• An adjustable wrench or the right size socket for the priming plug.
• Thread sealant tape or pipe dope for the plug threads.
• A rag and a bucket for spills.

How to prime a shallow well jet pump

These steps follow Goulds' instructions for its shallow well jet pumps. Other brands are similar, but check your manual for the plug locations.

Once the pump builds pressure and shuts off at cut-out, close the faucet and check the plug for leaks.

How to prime a deep well jet pump

Goulds says deep well single-stage and multi-stage jet pumps need a complete prime before starting. The process is the same as above: power off, fill through the priming port until the pump and lines are full, seal, restart. On vertical pumps, Goulds says priming goes through the pressure gauge port on the pressure control valve.

Deep well setups take more water because there are two pipes down the well to fill. Expect to repeat the fill more than once.

Priming a pump with a pressure tank

The tank doesn't change the steps. Open a faucet near the tank before you start so the system isn't pressurized, and keep the tank's valve open. Once the pump is primed, it refills the tank as usual. If the pump keeps losing prime and also cycles a lot, check the tank's air charge too; Goulds lists a waterlogged tank as a cause of excessive cycling.

Why it keeps losing prime

A pump that has to be reprimed every few days isn't a priming problem. Something is letting water drain back or air leak in.

• Leaking foot valve or check valve. Water runs back down the well overnight. Check this one first. See foot valve replacement.
• Air leak on the suction side. A loose fitting, cracked pipe or bad gasket lets air in. Run the pump and listen for a hiss at each joint, or brush soapy water on them.
• Water level too low. If the water drops below the foot valve or below the reach of suction, the pump sucks air. Goulds gives 25 feet as the practical suction lift at sea level.
• Too much lift for a shallow well pump. If the water has dropped below that range, a shallow well jet won't hold prime. A deep well jet or submersible is the fix.

The plastic priming plugs on many jet pumps crack if you crank on them. Hand-tight plus a little more, with fresh tape, is all they need.

Mistakes to avoid

• Running it dry to "see if it catches." Each dry run cooks the seal. Goulds warns that dry running damages the pump.
• Skipping the vent plug. Trapped air keeps the pump from filling completely.
• Not fixing the leak. If you prime it and it loses prime again, find the foot valve or fitting that's leaking.
• Using dirty water. You're pouring it into your drinking water supply.

When it's a pro job

Call a well contractor if the pump won't hold prime after two or three tries, the foot valve or deep well jet has to come out of the well, or the water level in the well seems to have dropped. HomeGuide puts a foot valve replacement at $150 to $400 and a check valve at $150 to $200. HomeAdvisor's labor figure averages $50 an hour, plus a house call fee of $100 to $150.