What Priming Means and Why Your Pump Needs It
Priming means filling the pump casing and intake line with water before you start the pump. A deep well pump cannot move water upward through an empty pipe — it needs water already present to create the pressure that pulls more water up from below. Without priming, the pump will run dry, draw in air instead of water, and either shut itself off or run until it overheats and breaks.
You will know your pump needs priming if you turn it on and hear it running but no water comes out of the faucet, or if water sputters and stops. This happens most often after you have drained the system for maintenance, replaced a pipe, or lost power for several hours.
Key Takeaways
- Priming fills the pump casing and the pipe from the pump down to the water with water before you start the motor, so the pump can pull water upward instead of air.
- You will need a bucket of water, a funnel, and access to the priming plug or priming port on top of the pump — the exact location depends on your pump model.
- Pour water slowly into the priming port until water flows back out or until the port overflows, then close the plug 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, and you will need to inspect those parts.
- Some modern pumps prime themselves automatically when you turn them on, so check your owner's manual before assuming you need to prime by hand.
Locate the Priming Port on Your Pump
The priming port is a small plug or valve on top of the pump casing, usually brass or plastic. On most submersible pumps, it sits on the discharge head — the part where the water line leaves the pump. On jet pumps (which sit above ground), the port is often on the side of the casing near the top.
If you cannot find it, check your pump's owner's manual or look for a small hole with a removable cap or a valve handle labeled "prime" or "vent." Some pumps have the priming port on the check valve instead of the pump itself. If your manual is missing, you can often find it online by searching your pump brand and model number.
Do not confuse the priming port with the pressure relief valve or the drain plug. The priming port is always on the discharge side (where water leaves), never on the intake side (where water enters from the well).
Gather Water and a Funnel
You will need a bucket of water — at least two to three gallons for most deep well pumps. Use water from a hose, a faucet, or even a neighbor's well if your own system is not working. The water does not need to be filtered or treated; it is only temporary and will be pushed back into the well once the pump starts.
A funnel makes pouring easier and reduces spills. If you do not have a funnel, you can roll a piece of paper or cardboard into a cone shape and tape it, or straightforward pour slowly and carefully into the opening. Have a rag or towel nearby to catch drips and wipe the area afterward.
Pour Water Into the Priming Port
Turn off the pump before you start. Open the priming port by unscrewing the plug or turning the valve handle counterclockwise. Place your funnel in the opening if you are using one.
Pour water slowly into the port. Watch for water to flow back out of the opening or for the port to overflow — this tells you the pump casing and the line down to the water are now full. On some pumps, you will see water come back up and out; on others, the water will straightforward fill the space inside and the port will overflow when full. Either way, keep pouring until you see this happen.
This usually takes one to two minutes. Do not rush — pouring too fast can trap air bubbles inside the casing, and you will have to start over. Once water overflows or flows back out, close the priming port by screwing the plug back in or turning the valve clockwise. Wipe away any spilled water.
Start the Pump and Check for Water Flow
Turn on the pump. Listen for the motor to run smoothly without a high-pitched whine or grinding sound. Within 30 seconds to two minutes, water should flow from your faucet or outdoor spigot. The first water may sputter or come out in bursts as remaining air leaves the line — this is normal.
Let the pump run for at least five minutes after water starts flowing steadily. This clears any remaining air from the system and allows the pump to reach its normal operating pressure. Check that water pressure feels normal — it should be strong and consistent, not weak or intermittent.
If no water appears after five minutes of running, turn the pump off and repeat the priming process. You may need to prime two or three times if the intake line is very long or if air pockets are trapped in the pipe.
Troubleshoot If the Pump Loses Prime Quickly
If the pump works for a few minutes and then stops, or if it loses prime again within hours or days, you have a leak or a valve problem. The most common cause is a leak in the intake line — the pipe running from the pump down into the well. Even a small hole will let air in and break the prime.
Check the entire visible length of the intake line for cracks, holes, or loose fittings. Look especially at joints and at the point where the line enters the ground. If you find a leak, you will need to replace that section of pipe or tighten the fitting. Do not try to patch it with tape — the pressure will push the patch off.
The second common cause is a faulty check valve. This one-way valve sits in the intake line and should hold water in the line even when the pump is off. If it leaks, water drains back down into the well and air enters the line. You will need to replace the check valve. This is a job for a well service professional if you are not comfortable working with pressurized plumbing.
When Your Pump Primes Itself Automatically
Some modern pumps, especially newer submersible models and certain jet pumps, have a built-in priming system that fills the casing automatically when you turn on the motor. Check your owner's manual to see if yours is one of these — if it is, you do not need to prime by hand.
If your manual says the pump is self-priming but it still does not produce water after running for several minutes, the self-priming system may have failed. In that case, you can try manual priming as described above. If manual priming works but the pump loses prime again, contact a well service technician — the self-priming mechanism may need repair or replacement.
Frequently Asked Questions
How do I know if my pump is primed or not?
A primed pump produces water within 30 seconds to two minutes of starting. An unprimed pump runs but produces no water, or produces only air and sputtering sounds. If you are unsure, turn on the pump and listen — a smooth, steady hum with water flowing means it is primed. A high-pitched whine or grinding sound usually means air is in the line.
Can I prime the pump from a faucet inside the house?
No. You must pour water into the priming port on the pump itself, not into a faucet. The faucet is downstream of the pump, and water poured there will not reach the pump casing or the intake line. Always prime at the pump.
What if I cannot find the priming port?
Check your pump's owner's manual by model number — most manufacturers post them online. If the manual is truly unavailable, contact the pump manufacturer directly with your model number, or hire a well service technician to locate it for you. Guessing and drilling holes will damage the pump.
How much water do I need to prime the pump?
Most deep well pumps need two to three gallons to fill the casing and intake line. You will know you have enough when water overflows from the priming port. If you run out before that happens, refill your bucket and keep pouring. The exact amount depends on how deep your well is and how long your intake line is.
Do I need to prime every time I turn on the pump?
No. Once primed, the pump should hold its prime as long as the system has no leaks and the check valve seals properly. You only need to prime again after you have drained the system, replaced a pipe, or if the pump loses prime on its own — which signals a leak or valve problem that needs repair.