Re-priming restores water flow when air enters the pump
A well pump loses its prime when air gets into the line instead of water. When this happens, the pump runs but delivers little or no water to your house. Re-priming means refilling the pump chamber with water so it can push water up from the well again. The process takes 15 minutes to an hour and requires no special tools beyond a bucket and a wrench you likely own.
Most homeowners can re-prime a pump themselves. The exact steps depend on whether you have a jet pump (shallow well, usually under 25 feet) or a submersible pump (deep well, usually 25 feet or deeper). Both types prime the same way: you pour water into the pump housing, close a valve, and let the pump draw water from the well. If re-priming does not work after two attempts, the problem is usually a leak in the intake line or a failed check valve, and you will need a pump technician.
Key Takeaways
- A pump loses prime when air enters the line, and re-priming means refilling the pump chamber with water from a bucket.
- Jet pumps have a priming plug on top of the pump housing; submersible pumps require you to open a valve on the pressure tank instead.
- You pour water in, close the valve or plug, and run the pump for 30 seconds to two minutes until water flows steadily from a faucet.
- If the pump still will not deliver water after two re-priming attempts, the intake line likely has a leak or the check valve has failed.
How to re-prime a jet pump
Jet pumps sit above ground and have a visible priming plug on top of the pump housing. The plug is usually a square or hex-shaped bolt about the size of a quarter. Turn off the pump at the breaker or switch before you start.
Use an adjustable wrench or socket to unscrew the priming plug counterclockwise. Water may drip out—this is normal. Fill a bucket with water from a faucet and slowly pour it into the hole until water overflows slightly. Screw the priming plug back in by hand, then tighten it with the wrench. Do not over-tighten; snug is enough.
Turn the pump back on. Walk to the nearest faucet and turn it on. You should hear the pump working harder than usual. Water may sputter or come out brown at first. Let it run for 30 seconds to two minutes. Once water flows clear and steady, turn off the faucet and the pump has re-primed. If no water comes out after two minutes, turn off the pump, wait five minutes, and repeat the process once more.
How to re-prime a submersible pump
Submersible pumps sit at the bottom of the well, so you cannot pour water directly into them. Instead, you open a valve on the pressure tank (the metal tank that stores water pressure in your system). The valve is usually a small brass fitting on the side or top of the tank, sometimes labeled "air valve" or marked with a small square or cross.
Turn off the pump at the breaker. Locate the pressure tank valve and place a bucket underneath it to catch water. Use an adjustable wrench to open the valve slowly by turning counterclockwise. Water should flow out. Once water stops dripping, close the valve by turning it clockwise. Do not force it.
Turn the pump back on and listen. The pump should run and pull water from the well into the tank. Walk to a faucet and turn it on. Water may sputter or come out discolored for the first 30 seconds to two minutes. Once it flows clear and steady, the pump has re-primed. If nothing comes out after two minutes, turn off the pump, wait five minutes, and repeat the valve-opening step once more.
Why a pump loses prime in the first place
A pump loses prime because air enters the intake line between the well and the pump. This usually happens after the power goes out, when the pump shuts down and water drains backward out of the line. Air rushes in to fill the space. It can also happen if the intake line develops a small leak or crack—air gets sucked in instead of water.
Losing prime once is not unusual and does not mean the pump is failing. Losing prime repeatedly (more than once a month) usually points to a leak in the intake line or a failed check valve. A check valve sits in the well or at the pump intake and is supposed to let water flow up but not back down. When it fails, water drains out of the line every time the pump stops, and air enters. This requires a pump technician to diagnose and repair.
What to do if re-priming does not work
If the pump still will not deliver water after you have re-primed it twice, stop and do not keep trying. Repeated re-priming without success usually means one of two things: the intake line has a leak, or the check valve has failed. Neither one is a repair you can do yourself.
A leak in the intake line is often small and hard to spot. Water leaks out of the line, air gets sucked in, and the pump cannot build enough pressure to push water up. A failed check valve lets water drain backward out of the line when the pump is off, so re-priming works only until the pump stops and the water drains again. Both problems require a pump technician to locate and fix. Call a local well service company and describe what you have tried—they can usually diagnose the problem over the phone and give you a cost estimate.
Preventing loss of prime
You cannot always prevent a pump from losing prime, but you can reduce how often it happens. Check the intake line once a year for cracks, leaks, or loose fittings. Look where the line enters the ground and where it connects to the pump. Tighten any loose fittings by hand or with a wrench.
If your area has frequent power outages, ask a pump technician whether your system has a check valve. If it does not, installing one is inexpensive and can prevent the pump from losing prime every time the power goes out. A check valve costs between $50 and $150 in parts and labor, depending on where it needs to go.
Keep the priming plug or valve accessible. Do not paint over it or let debris pile around it. The easier it is to reach, the faster you can re-prime if you need to.
Frequently Asked Questions
Can I re-prime a pump if the well has run dry?
No. Re-priming works only if water is still in the well. If the well has run dry, pouring water into the pump will not help—the pump cannot pull water from a well that has no water in it. Wait for the water table to recover or contact a well service company to check the well depth and water level.
How often should I re-prime my pump?
A healthy pump should not need re-priming more than once or twice a year, usually after a power outage. If you are re-priming more than once a month, the intake line likely has a leak or the check valve has failed. Have a pump technician inspect the system.
What if water comes out brown or rusty after re-priming?
Brown or rusty water is normal for the first minute or two after re-priming. It is sediment from the well and intake line. Let the water run until it clears. If it stays brown or rusty after five minutes, turn off the pump and wait an hour before trying again. Persistent discoloration may mean sediment is clogging the intake screen.
Do I need to turn off the pump before re-priming?
Yes. Always turn off the pump at the breaker or switch before opening the priming plug or pressure tank valve. This prevents water from spraying out and keeps you safe from the pump suddenly starting while you are working on it.
Can I use a garden hose to pour water into a jet pump instead of a bucket?
Yes, a garden hose works fine. Fill the pump housing until water overflows, then close the priming plug. A bucket is simpler because you can control the flow better and see exactly how much water you are pouring in, but either method works.