Priming fills the pump chamber with water so it can draw from the well
A well pump loses its prime when air enters the pump chamber — usually after you've shut it down for maintenance, drained the system, or run the well dry. Without water in the chamber, the pump cannot create the suction needed to pull water up from below. Priming means refilling that chamber with water by hand before you restart the pump, so it can work normally again.
Without a pressure tank, you are working with a jet pump or shallow-well pump that relies on continuous priming to function. The process is straightforward: you pour water into the pump intake until the chamber is full, then start the pump. The water already in the chamber gives the pump something to work with, and it can then draw fresh water from the well.
The exact steps depend on your pump model and where the priming port is located, but the principle is the same across all shallow-well and jet pump setups.
Key Takeaways
- Priming requires pouring water directly into the pump chamber through a priming port or the top of the pump housing until water flows out steadily.
- You will need a bucket of water, a funnel, and a wrench or screwdriver to open the priming port — most are located on top of the pump or on the intake line.
- After priming, start the pump and listen for normal operation; if it loses prime again within minutes, check for air leaks in the intake line or a cracked pump housing.
- Keeping the intake line submerged and free of cracks prevents most priming problems and reduces how often you need to prime by hand.
Locate the priming port on your pump
The priming port is a small opening, usually a plug or cap, on the top or side of the pump housing. On most jet pumps, it sits directly above the pump body. On some shallow-well centrifugal pumps, it may be on the intake line just below the pump. Check your pump's manual first — the location varies by manufacturer and model year.
If you cannot find the manual, look for a brass or plastic plug roughly the size of a dime or quarter on the pump itself. It is often labeled "prime" or straightforward left unmarked. If the pump has a clear plastic housing or sight glass, the priming port is usually near that. On older cast-iron pumps, the port may be a small threaded hole with a removable cap.
Do not confuse the priming port with the drain plug (usually at the bottom of the pump) or the pressure relief valve (if your pump has one). The priming port is the one you pour water into, not drain from.
Gather water and tools before you start
You will need a bucket of water — at least two to three gallons — a funnel, and either a wrench or screwdriver to open the priming port. Use a wrench if the port is a hex plug; use a screwdriver if it is a slotted cap. Keep the water nearby so you do not have to leave the pump unattended once you start.
If the priming port is tight or corroded, explore penetrating oil (like WD-40) and wait five to ten minutes before trying to open it. This prevents you from stripping the threads or cracking a plastic cap. Have a rag or small bucket ready to catch any water that drips when you open the port.
Turn off the pump and the circuit breaker before you begin. Do not attempt to prime a running pump.
Open the priming port and pour water into the pump
Using your wrench or screwdriver, slowly unscrew or unplug the priming port. Water or air may escape — this is normal. Once the port is open, place your funnel in the opening and begin pouring water from your bucket into the pump chamber.
Pour steadily and watch the water level inside the pump. You will see water fill the chamber. Keep pouring until water flows out of the priming port itself — this means the chamber is completely full and all air has been pushed out. This usually takes one to three gallons, depending on pump size.
Once water flows from the port, stop pouring. Screw the priming port cap back in firmly but do not overtighten it — you risk cracking the threads or the pump body. Wipe away any spilled water.
Start the pump and listen for normal operation
Turn the circuit breaker back on and start the pump. A properly primed pump should begin drawing water within a few seconds. You will hear a change in sound — the motor will settle into a steady hum, and you should feel vibration from the pump body as water moves through it.
Let the pump run for one to two minutes. Check the pressure gauge (if you have one) or listen for water flowing from the discharge line. If water comes out, the prime held and the pump is working. If the pump makes a grinding or cavitating sound (like marbles in a can), it may have lost prime again — turn it off when ready and repeat the priming process.
Do not run a pump without prime for more than a few seconds. Running dry damages the pump seals and can overheat the motor.
Check for air leaks if the pump loses prime repeatedly
If the pump loses prime within minutes of starting, air is entering the system somewhere. The most common source is a crack or loose fitting in the intake line — the pipe that runs from the well to the pump. Inspect the entire intake line for visible cracks, splits, or white mineral deposits (which indicate a slow leak).
Check all threaded connections on the intake line and tighten them with a wrench if they are loose. Even a slightly loose fitting will suck air into the line and break the prime. If you find a crack in a plastic or PVC intake line, you will need to replace that section of pipe — patching does not hold under suction.
Also check the pump housing itself for cracks, especially around the priming port. A cracked housing cannot hold prime and will need replacement. If the pump is old and cracks appear, it is usually cheaper to replace the pump than to repair it.
Keep the intake line submerged to reduce priming problems
The intake line must stay underwater at all times. If the water level in your well drops below the intake line opening, the pump will lose prime and cannot draw water. This is especially common in shallow wells during dry seasons or if the well is not deep enough for the pump model you have.
If your well is shallow, consider installing a deeper well or switching to a submersible pump, which sits at the bottom of the well and does not need priming. If deepening the well is not an option, you may need to prime the pump more often during low-water periods.
Inspect the intake line screen (the filter at the bottom of the line) at least once a year. A clogged screen reduces water flow and can cause the pump to lose prime under load. Clean or replace the screen if it is visibly dirty or blocked.
Frequently Asked Questions
How often do I need to prime my well pump?
A healthy pump with no air leaks should hold prime indefinitely once started. If you are priming more than once a month, you have an air leak in the intake line or pump housing. Check for cracks, loose fittings, or a screen that is clogged. Frequent priming is a sign something needs repair.
Can I use any water to prime the pump?
Yes. Use tap water, well water, or even rainwater from a bucket. The water you pour in is just to fill the chamber — it will be pushed out once the pump starts drawing from the well. Do not use salt water or contaminated water if you can avoid it, as it may damage seals or corrode the pump interior.
What if water will not flow out of the priming port even after I pour in several gallons?
The port may be clogged with mineral deposits or debris. Try opening the port, inserting a thin wire or straightened paper clip, and gently probing to clear the blockage. If that does not work, the pump may have an internal blockage or a failed check valve. You may need to have the pump serviced or replaced.
Is it normal for the pump to make noise right after priming?
A brief grinding or sputtering sound as the pump starts is normal — it is air leaving the system. If the noise continues for more than a few seconds or sounds like marbles rattling, turn the pump off. This usually means the pump is cavitating (running without enough water) and needs to be primed again.
Do I need to prime the pump every time I turn it on?
No. Once primed and running, the pump should stay primed as long as the intake line stays submerged and there are no air leaks. You only need to prime after maintenance, after the well runs dry, or if you notice the pump has lost prime during operation.