What Priming Means and Why Your Pump Needs It
Priming means filling the pump casing and intake line with water before you turn on the motor. A shallow well pump cannot draw water up from the ground on its own—it needs water already inside the system to create the suction that pulls more water up. Without priming, you will turn on the pump, hear it run, and get no water out.
Shallow well pumps sit above ground (usually within 25 feet of the water surface), so gravity works against you. The pump must be primed after installation, after the system has sat unused for weeks, or after you have drained the line for maintenance. Once primed and running, the pump stays primed as long as water keeps flowing and no air leaks into the line.
Key Takeaways
- Priming fills the pump casing and intake line with water so the pump can create suction and draw water from the well.
- You will need a bucket of water, a funnel, and access to the pump's priming plug or top opening, which varies by pump model.
- Pour water into the pump until it overflows slightly, then close the priming plug and run the pump for 30 seconds to one minute before water flows.
- If water does not flow after priming, check for air leaks in the intake line, cracks in the casing, or a check valve stuck closed.
- Priming is a one-time task after installation or maintenance; a running pump stays primed on its own.
Locate the Priming Plug or Access Point
Every shallow well pump has a way to add water for priming, but the location and design differ by manufacturer. Look at the top of the pump casing for a priming plug—a removable cap or bolt, usually brass or plastic, roughly the size of a quarter to a half-dollar. Some pumps have a priming port with a small valve; others have a larger opening on top of the casing itself.
Check your pump's manual or the nameplate on the motor housing to identify the exact location. If you cannot find the manual, photograph the pump model number and search online for the manufacturer's diagram. Do not guess—pouring water into the wrong opening can damage the motor or electrical connections.
Gather Water and a Funnel
Fill a bucket with water from a working faucet, a neighbor's well, or any clean water source. You will need roughly one to three gallons, depending on the pump size and how long the intake line is. A longer intake line (one that runs deeper or farther horizontally) holds more water and requires more priming water.
Get a funnel that fits the priming plug or opening. A standard kitchen funnel works for most plugs. If the opening is very small, use a funnel with a narrow spout, or roll a piece of paper into a cone. Avoid funnels with metal screens or filters—they slow the pour and trap air bubbles.
Pour Water Into the Pump Casing
Remove the priming plug by turning it counterclockwise by hand or with a wrench, depending on the type. Set it aside where you will not lose it. Place the funnel in the opening and pour water slowly and steadily into the pump. Watch the water level rise inside the casing.
Keep pouring until water begins to overflow slightly from the opening—this means the casing and the intake line are full. Overflowing confirms that air pockets have been pushed out. Stop pouring once you see water spilling out, then when ready screw the priming plug back in by hand. Tighten it firmly but do not force it; you can crack the casing or strip the threads.
Run the Pump and Check for Water Flow
Turn on the pump motor using the switch or control panel. The pump will run, and you should hear it working. In the first 30 seconds to one minute, water should begin flowing from the discharge line or faucet. If water flows when ready, priming was successful and you are done.
If no water flows after one minute of running, turn off the pump and wait a few minutes. Sometimes air trapped deeper in the line takes longer to work its way out. Repeat the priming process: remove the plug, pour more water until it overflows, close the plug, and run the pump again for another minute. Most pumps prime on the second or third attempt.
Troubleshoot If Water Still Does Not Flow
If the pump runs but produces no water after three priming attempts, the problem is usually an air leak in the intake line. Check the entire intake line from the pump down to the well for cracks, loose fittings, or holes. Even a pinhole leak will let air in and break the seal. Tighten all connection points with a wrench, and look for visible damage or corrosion.
A second common cause is a check valve stuck in the closed position. The check valve sits in the intake line and prevents water from flowing backward when the pump stops. If it is stuck, water cannot flow forward either. You may hear the pump running but feel no vibration in the discharge line. A plumber can test and replace a stuck check valve.
A cracked pump casing or a failed internal seal will also prevent priming from working. If the casing is visibly cracked or leaking water from seams, the pump needs replacement. If you see no visible damage and all connections are tight, the pump likely has an internal failure and should be inspected by a well service technician.
Prevent Loss of Prime During Storage
Once your pump is primed and running, it will stay primed as long as water flows and no air enters the line. If you plan to shut down the system for more than a few weeks, drain the pump and intake line to prevent freeze damage in winter or stagnant water in summer. When you restart, you will need to prime again.
To keep a pump primed during short shutdowns (a few days to a week), close the discharge valve if your system has one. This traps water inside the pump and line. When you restart, open the valve and the pump should resume flow without re-priming. If you do not have a discharge valve, the pump will lose prime over time as water seeps back down the intake line, and you will need to re-prime.
Frequently Asked Questions
Can I prime a shallow well pump without a bucket of water?
No. The pump cannot create suction from an empty casing, so you must pour water in to start the process. If you have no clean water available, ask a neighbor or use water from a working faucet. Even one gallon is usually enough to prime most shallow well pumps.
How long does priming take?
Pouring water into the pump takes two to five minutes. After you close the priming plug and turn on the motor, water should flow within 30 seconds to one minute. If it does not, you may need to repeat the process, which adds another few minutes. The entire job usually takes 10 to 20 minutes.
What if I cannot find the priming plug?
Check the pump manual or contact the manufacturer with your pump model number. Some older or specialty pumps have the priming port in an unusual location, or it may be labeled differently. A well service technician can also locate it if you are unsure.
Will priming damage the pump motor?
No, priming is a normal part of pump operation and does not harm the motor. The motor is designed to run dry for short periods during priming. However, do not run the pump for more than a few minutes without water flowing out—prolonged dry running can overheat the motor.
Do I need to prime the pump every time I turn it on?
No. Once primed and running, the pump stays primed as long as the system is sealed and water keeps flowing. You only need to prime after installation, after draining the line for maintenance, or after the system has sat unused for several weeks.