Priming fills your pump with water so it can start working
Priming means filling your well pump with water before you turn it on for the first time or after it has run dry. Without water inside the pump chamber, the pump cannot create the suction needed to pull water up from the well. If you start a dry pump, it will run but pull nothing, and you risk damaging the internal parts. Priming takes 15 to 30 minutes and requires only a bucket of water and access to the pump's priming port or top cover.
You will know your pump needs priming if water stops flowing from your taps even though the well has water in it, or if you have just installed a new pump. Priming is not the same as bleeding air from the lines—that happens after priming and removes trapped air bubbles. Priming comes first and is the foundation step.
Key Takeaways
- Priming fills the pump chamber with water so it can create suction and draw water from the well.
- Most jet pumps have a priming port on top; centrifugal pumps may require removing the top cover to access the chamber.
- You pour water directly into the pump until it overflows slightly, then close the port or cover and start the pump.
- If the pump loses prime again within hours or days, the problem is usually a leak in the intake line or a check valve that is not sealing.
- Priming is a one-time task after installation or after the pump runs dry; normal operation does not require repeated priming.
Locate the priming port or access point on your pump
The location depends on your pump type. Jet pumps (the most common type for residential wells) have a small brass or plastic port on the top of the pump housing, usually marked "Prime" or with a plug. This port is where you pour water in. Look for a threaded opening about the size of a dime or quarter on the uppermost part of the pump casing.
Centrifugal pumps do not always have a dedicated priming port. Instead, you may need to remove the bolts holding the pump's top cover or volute and lift it off to expose the impeller chamber. Check your pump's manual or the manufacturer's label on the pump body to confirm which type you have and where to access the chamber.
If you cannot find a priming port and your pump has no removable cover, contact the pump manufacturer or a well contractor. Some submersible pumps and specialty models require different priming methods.
Gather water and prepare the pump
You will need a bucket of water from any source—tap water, a hose, or collected rainwater works fine. The water does not need to be from the well. Have the bucket ready before you start, so you are not scrambling mid-task.
Turn off the pump's power switch or breaker before you begin. This is essential for safety. You do not want the pump to start while you are pouring water into it. Leave the power off until you have finished priming and closed the priming port or cover.
If your pump has a pressure tank, check that the tank's air valve (a small Schrader valve on top, like a car tire valve) is not stuck or blocked. A blocked air valve can prevent the pump from building pressure after priming. If the valve looks corroded or will not move, have it serviced before priming.
Pour water into the priming port until it overflows
Slowly pour water from your bucket into the priming port. Watch the water level inside the pump. You are filling the pump chamber and the intake line leading down to the well. Pour steadily but do not rush; you want to fill the chamber completely and push out any air pockets.
Continue pouring until water begins to overflow from the priming port or from the pump outlet (the pipe leading to your house). This overflow means the chamber is full and air has been displaced. Stop pouring once overflow begins. If the water level drops as you pour, keep pouring until it stays at the overflow point—this means air pockets are still being filled.
Some pumps have a small air vent screw near the priming port. If yours does, you can open this vent slightly while pouring to let trapped air escape faster. Close it once water flows from the vent.
Close the priming port and turn on the pump
Once water overflows, when ready close the priming port by screwing the plug back in hand-tight. Do not over-tighten; you can crack the plastic or strip the threads. If you removed a cover instead of using a port, replace the bolts and tighten them in a crisscross pattern (like tightening a car wheel) to seal evenly.
Turn the pump's power switch or breaker back on. The pump should start when ready. Listen for normal operation—a steady hum and vibration. Water should begin flowing from your taps within 30 seconds to a minute. If nothing happens after two minutes, turn the pump off and wait five minutes before trying again. Sometimes a pump needs a moment to build pressure.
If water still does not flow after a second attempt, the pump may have lost prime again, which signals a leak or a faulty check valve (see the troubleshooting section below).
Bleed air from the lines after priming
Once water flows from your taps, you may notice sputtering, spitting, or air bubbles in the water. This is normal and means air is still trapped in the pipes. This is the bleeding phase, which is separate from priming. Open the lowest tap in your house (usually a basement or outdoor faucet) and let it run for two to five minutes. Air will escape and the water will become clear and steady.
If you have multiple taps, open a few of them to speed up air removal. Do not worry about wasting water; this step is necessary for the pump to work smoothly. Once all taps flow clear water without sputtering, the pump is fully primed and bled.
Troubleshoot if the pump loses prime repeatedly
If the pump works for an hour or two and then stops, or if it loses prime within a day, the problem is usually a leak in the intake line (the pipe running from the pump down into the well) or a faulty check valve. A check valve is a one-way valve that prevents water from flowing backward down the well when the pump stops. If it does not seal, water drains back down and the pump loses its prime.
To check for a leak, look at the intake line where it enters the ground or the well casing. If you see water dripping or pooling, there is a leak. Small leaks can sometimes be sealed with plumber's tape or epoxy putty as a temporary fix, but the line should be replaced if the leak is large or the tape does not hold.
If the intake line looks dry but the pump still loses prime, the check valve is likely the culprit. Check valves are inexpensive (usually $20 to $50) and are located at the bottom of the intake line or just above the pump. A well contractor can replace it in an hour. Until then, you will need to re-prime the pump each time it loses prime, which is inconvenient but not dangerous.
Frequently Asked Questions
How often do I need to prime my pump?
Under normal conditions, you should never need to prime again after the initial priming. If your pump loses prime regularly, something is wrong—usually a leak or a faulty check valve. A well contractor should inspect the system to find and fix the problem.
Can I use well water to prime, or does it have to be tap water?
Either works. Well water is fine if you have access to it, but tap water is easier and more convenient. The source does not matter because the pump will draw from the well once it is running.
What if water does not overflow from the priming port no matter how much I pour?
This usually means the intake line is blocked or the pump chamber has a large air pocket that is hard to fill. Try pouring more slowly and wait between pours to let air escape. If overflow never happens after 10 minutes of steady pouring, stop and contact a well contractor—there may be a blockage or a damaged internal part.
Is it safe to prime the pump myself, or should I call a contractor?
Priming is safe to do yourself if you turn off the power first and follow the steps carefully. It requires no special tools or knowledge. However, if the pump does not respond after priming, or if it loses prime repeatedly, a contractor should diagnose the problem.
Can I damage the pump by priming it wrong?
Not easily. The main risk is running the pump dry (without priming), which can damage the impeller over time. Priming itself—pouring water into the port—cannot hurt the pump. The only mistake to avoid is over-tightening the priming port plug, which can crack plastic fittings.