How to Prime a Well Pump
Updated March 2, 2026
Re-prime a shallow well jet pump that has lost its prime -- the step-by-step process to get water flowing again after the pump runs dry.
Overview
A well pump that loses its prime runs but produces no water. The impeller spins in air instead of water, and air cannot create the suction needed to pull water from the well. Shallow well jet pumps (above-ground, suction-type) lose prime when air enters the suction line -- from a leak in the pipe, a failed foot valve at the bottom of the well, or running the pump dry during a drought. Deep well submersible pumps rarely lose prime because they sit underwater. This guide covers re-priming a shallow well jet pump, the most common residential well pump that needs priming.
What You'll Need
Safety First
- Turn off the pump breaker before opening the priming plug. The pump should not be running while you add water to the housing.
- Do not run a jet pump dry for more than 30 seconds. The mechanical seal relies on water for lubrication and cooling. Dry running destroys the seal in minutes -- a $200-$400 repair.
- Well water is not treated. If you prime with water from another source (hose from a neighbor, bottled water), the introduced water should be potable.
Step-by-Step Instructions
- Turn Off the Pump and Locate the Priming Plug
Flip the pump breaker off. The priming plug is on top of the pump housing -- a large hex plug (usually 1-inch or 1-1/4 inch) that threads into the volute (the snail-shaped housing around the impeller). Some pumps have a dedicated priming port with a smaller plug. Unscrew the plug counterclockwise. You may hear air hiss out -- that confirms air in the housing where water should be.
Tip: If you cannot find the priming plug, check the owner's manual. On most residential jet pumps (Goulds, Flotec, Wayne, Sta-Rite), the plug is the largest hex fitting on the top of the pump body. - Fill the Pump Housing with Water
Pour clean water into the priming port until the housing is completely full. Use a funnel to avoid spilling. A typical jet pump housing holds 1-2 quarts. Pour slowly and let air bubbles escape through the port. When water reaches the port opening and stays at that level without dropping, the housing is full. If the water level drops immediately, air is being pulled in from the suction line -- there is a leak or the foot valve has failed (see troubleshooting below).
Tip: Use a garden hose connected to a neighbor's outdoor faucet or a jug of water. You need 1-2 gallons to fill the housing and the initial section of suction pipe. Keep pouring until no more air bubbles escape. - Close the Plug and Start the Pump
Thread the priming plug back in hand-tight, then snug with a wrench (do not overtighten -- just snug enough to seal). Turn the pump breaker on. The pump should start and begin pulling water from the well. Listen: you should hear the pitch change from a high whine (air) to a lower hum (water) within 30-60 seconds. Check the pressure gauge -- it should climb to the cut-out pressure (typically 40-60 PSI) and the pump should shut off. If the pump runs for 60 seconds without building pressure, turn it off and repeat the priming process.
Tip: It may take 2-3 priming attempts to purge all the air from the suction line, especially if the well is deep (close to the 25-foot suction limit for jet pumps). Each attempt pushes more air out and pulls more water in. - Troubleshoot If Priming Fails
If the pump will not hold prime after 3 attempts, one of three things is wrong. Suction line leak: air enters through a crack, loose fitting, or corroded joint in the suction pipe between the pump and the well. Check every fitting for air leaks (apply soapy water and look for bubbles while the pump runs). Foot valve failure: the foot valve at the bottom of the suction line in the well allows water in but prevents it from draining back. If the valve is stuck open or the screen is damaged, water drains back to the well when the pump stops. Replace the foot valve ($15-$30). Well water level dropped below the suction line: during drought, the water table may drop below the reach of the suction pipe. Wait for the water level to recover or lower the foot valve deeper.
Tip: A foot valve that allows water to drain back is the most common cause of repeated prime loss. The pump primes, runs fine for hours, then loses prime when it shuts off because the water in the suction line drains back to the well through the failed valve.
Pro Tips
- Jet pumps have a maximum suction lift of 25 feet. If the water level in the well drops below 25 feet from the pump, the pump physically cannot pull water regardless of priming. This is a fundamental physics limitation of suction pumps. A deep well submersible pump ($500-$1,500 installed) sits in the water and pushes it up instead of pulling it.
- Install a check valve on the suction line near the pump in addition to the foot valve at the bottom of the well. The check valve prevents water in the housing from draining back if the foot valve fails.
- If the pump loses prime every time it shuts off, the foot valve or check valve has failed. Replacing both ($20-$50 total) solves the problem permanently.
- A pressure tank that is waterlogged (no air charge) causes the pump to short-cycle, which can push air into the system and cause prime loss. Check the tank air charge with a tire gauge on the Schrader valve -- it should match the cut-in pressure minus 2 PSI.
- Keep a gallon jug of water near the pump for emergency priming. During a power outage, the pump may lose prime when power is restored if the foot valve leaks slowly.
When to Call a Pro
Call a well pump specialist if the pump will not hold prime after checking the foot valve and suction line (may indicate a cracked impeller, failed mechanical seal, or a problem deep in the well), if the well water level has dropped and you need a deeper pump or a new well, or if the pump is a submersible (deep well) that has lost pressure -- submersibles do not lose prime in the traditional sense; pressure loss indicates pump failure or a hole in the drop pipe.
Frequently Asked Questions
When should I call a plumber to prime a well pump?
Call a well pump specialist if the pump will not hold prime after checking the foot valve and suction line (may indicate a cracked impeller, failed mechanical seal, or a problem deep in the well), if the well water level has dropped and you need a deeper pump or a new well, or if the pump is a submersible (deep well) that has lost pressure -- submersibles do not lose prime in the traditional sense; pressure loss indicates pump failure or a hole in the drop pipe.
What are some expert tips to prime a well pump?
Jet pumps have a maximum suction lift of 25 feet. If the water level in the well drops below 25 feet from the pump, the pump physically cannot pull water regardless of priming. This is a fundamental physics limitation of suction pumps. A deep well submersible pump ($500-$1,500 installed) sits in the water and pushes it up instead of pulling it. Install a check valve on the suction line near the pump in addition to the foot valve at the bottom of the well. The check valve prevents water in the housing from draining back if the foot valve fails. If the pump loses prime every time it shuts off, the foot valve or check valve has failed. Replacing both ($20-$50 total) solves the problem permanently. A pressure tank that is waterlogged (no air charge) causes the pump to short-cycle, which can push air into the system and cause prime loss. Check the tank air charge with a tire gauge on the Schrader valve -- it should match the cut-in pressure minus 2 PSI. Keep a gallon jug of water near the pump for emergency priming. During a power outage, the pump may lose prime when power is restored if the foot valve leaks slowly.
What tools do I need to prime a well pump?
You will need: Adjustable wrench (for the priming plug), Funnel (for pouring water into the priming port), 1-2 gallons of clean water (for filling the pump housing), Flashlight (for inspecting suction line fittings), Soapy water spray bottle (for detecting air leaks in suction line).
When should I call a professional instead of doing this myself?
Call a well pump specialist if the pump will not hold prime after checking the foot valve and suction line (may indicate a cracked impeller, failed mechanical seal, or a problem deep in the well), if the well water level has dropped and you need a deeper pump or a new well, or if the pump is a submersible (deep well) that has lost pressure -- submersibles do not lose prime in the traditional sense; pressure loss indicates pump failure or a hole in the drop pipe.
How difficult is this project?
This project is rated intermediate. It requires moderate DIY skill and the right tools.
How long does this take?
Plan for approximately 15 - 45 minutes. First-timers may need extra time.
How much will this cost?
The estimated cost is $0. Costs vary by location and materials chosen.