Priming a well pump means filling the pump chamber with water so it can draw water from the well

A well pump loses its prime when air enters the pump chamber — usually after the well runs dry, during maintenance, or if the pump sits unused for weeks. Without water in the chamber, the pump cannot create the suction needed to pull water up from below. Priming refills that chamber so the pump can work again. You can do this yourself with a garden hose in about 10 to 15 minutes, and it costs nothing beyond the water you use.

The process is straightforward: you pour water into the pump's priming port (a small opening on top or the side of the pump) until water comes out the discharge line, then run the pump. The hardest part is finding the priming port on your specific pump model — it is usually a threaded hole with a plug or cap, roughly the size of a quarter.

Key Takeaways

  • Locate the priming port on your pump — it is a small threaded hole, usually on the pump body itself, and may have a removable cap or plug.
  • Turn off the pump and close any isolation valves between the pump and the well before you start.
  • Pour water from a garden hose into the priming port until water flows out the discharge line, then replace the cap and turn the pump on.
  • If water does not flow out the discharge line after two or three minutes of pouring, the pump may have a deeper problem and you should stop and check the pump manual.
  • The pump should run for 30 seconds to one minute after priming; if it shuts off, it may need priming again.

Locate the priming port before you start

The priming port is a small threaded hole on the pump body, usually capped with a plastic or metal plug. On centrifugal pumps (the most common type for wells), it is often on the top or side of the pump housing. On some models, especially older ones, it may be on the discharge line itself, just above the pump. Check your pump's nameplate or manual for the exact location — the manual will have a diagram.

If you cannot find the manual, look for a small hole about the size of a pencil eraser with a cap or plug that you can unscrew by hand or with a wrench. Do not confuse it with the vent hole (which is usually smaller and has a screen) or the drain plug (which is at the bottom of the pump). When in doubt, take a photo of your pump and search online for "[pump brand and model] priming port" — you will usually find a diagram within a few results.

Turn off the pump and relieve pressure

Before you open the priming port, switch off the pump at the breaker or switch. If your system has an isolation valve between the pump and the well (a ball valve you can turn by hand), close it. This prevents water from flowing backward into the well while you are priming.

Wait 30 seconds for any pressure in the pump to drop. If your pump is connected to a pressure tank, you may hear a slight hiss as air escapes — this is normal. Do not open the priming port while pressure is still in the system; you could get sprayed with water or damage the pump seal.

Pour water into the priming port

Unscrew the cap or plug from the priming port. Attach your garden hose to a nearby faucet or have someone hold it ready. Position a bucket underneath the discharge line (the pipe coming out of the pump) to catch water.

Pour water slowly and steadily into the priming port. You are filling the pump chamber, so it will take a minute or two before water appears at the discharge line. Keep pouring until water flows out the discharge line in a steady stream with no air bubbles. This means the chamber is full and the air is pushed out. Once water is flowing, pour for another 10 to 15 seconds, then stop and replace the cap.

If no water comes out the discharge line after two to three minutes of pouring, stop. This usually means the pump intake is blocked, the well is dry, or there is a leak in the suction line. Do not keep pouring — you will waste water and may damage the pump. Check the well level and the intake line before trying again.

Turn the pump on and listen for normal operation

Once the cap is back on the priming port, turn the pump on at the breaker or switch. The pump should start when ready and run smoothly. You should hear water moving through the discharge line within the first few seconds. If the pump is primed correctly, it will run quietly and steadily.

Let the pump run for 30 seconds to one minute. Then turn it off and check for leaks around the priming port cap — tighten it by hand if water is seeping out. Turn the pump back on. If it runs without stopping and water flows normally from your faucets or outdoor lines, the priming worked.

What to do if the pump loses prime again quickly

If the pump runs for a few minutes and then shuts off, or if you have to prime it again within a few days, something is letting air into the system. The most common causes are a leak in the suction line (the pipe between the well and the pump), a cracked pump seal, or a water level that is dropping faster than the pump can keep up.

Check all visible pipes and connections between the well and the pump for cracks, loose fittings, or water dripping. Tighten any loose connections with a wrench. If you see a crack or the leak is inside the well casing, you will need a pump technician. If the well itself is running dry, you may need to lower the pump intake or have the well serviced.

Common mistakes that prevent priming from working

The most common mistake is pouring water too fast and not waiting long enough for the chamber to fill. If you pour a gallon in 10 seconds, most of it runs out the discharge line before the chamber fills. Pour slowly — it should take at least a minute for water to reach the discharge line.

Another mistake is opening the priming port while the pump is running or while pressure is still in the system. Always turn the pump off and wait 30 seconds before opening the cap. A third mistake is confusing the priming port with the vent hole or drain plug — opening the wrong hole will not prime the pump and may damage it. If you are unsure, consult the manual or call a pump technician before you open anything.

Finally, do not assume the pump is primed just because water came out the discharge line once. The chamber must be completely full and all air must be out. If you see any air bubbles in the water flowing from the discharge line, keep pouring until the water runs clear and steady.

Frequently Asked Questions

Can I prime the pump without turning it off first?

No. Opening the priming port while the pump is running can spray you with pressurized water and damage the pump seal. Always turn off the pump and wait 30 seconds before opening the cap. If your system has an isolation valve, close it too.

How much water should I pour into the priming port?

Pour slowly until water flows out the discharge line in a steady stream with no air bubbles, then pour for another 10 to 15 seconds. This usually takes one to two minutes and uses about two to five gallons, depending on the pump size. Stop if no water appears after three minutes of pouring.

What if I cannot find the priming port on my pump?

Check your pump's manual — it will have a diagram showing the exact location. If you do not have the manual, search online for your pump's brand and model number plus "priming port". You can also take a photo and post it on a well pump forum or call a local pump technician for help identifying it.

Do I need to prime the pump every time I turn it on?

No. A properly functioning pump should hold its prime indefinitely. If you have to prime it more than once a month, there is likely a leak in the suction line, a cracked seal, or a dropping water level. Have the system checked by a technician.

Can I use a submersible pump the same way?

No. Submersible pumps sit inside the well and do not need priming — they are always surrounded by water. Priming is only for centrifugal or jet pumps that sit above ground. If you have a submersible pump and it is not delivering water, the problem is usually a clogged intake or a power issue, not loss of prime.