Why You Need to Prime Your Well Pump
Priming means filling the pump chamber with water before you start it. A well pump cannot move water if air is in the lines—it will just spin without pulling anything up. When you first install a pump, drain the system for repairs, or the pump runs dry, you have to prime it by hand before it will work.
The water bucket method is the simplest approach for shallow wells (under 25 feet deep) and requires no special tools beyond what most households have. You pour water directly into the pump housing until it fills the chamber and the connected pipes, forcing out the air. Once primed, the pump can do its job.
Key Takeaways
- Priming fills the pump chamber with water so the pump can create suction and pull water from the well instead of just spinning with air inside.
- The bucket method works by pouring water into the top of the pump housing until water comes out the discharge pipe, which means the air is gone.
- You will need a bucket, a funnel (or a piece of cardboard rolled into one), and access to a water source—a hose, another well, or stored water.
- After priming, start the pump when ready and watch for water flow within 30 seconds; if nothing comes out, the prime was lost and you must repeat the process.
- If the pump will not hold prime after multiple attempts, the problem is usually a leak in the suction line or a check valve that is stuck, not the priming itself.
Gather Your Materials and Check the Setup
Before you start, locate the pump's priming plug or access point. Most centrifugal pumps (the most common type for wells) have a threaded hole on top of the pump housing, usually marked "Prime" or "Fill". Some pumps have a removable cap instead. Check your pump's manual to find the exact location—if you cannot find it, look for the highest point on the pump body itself.
Collect a bucket (5-gallon is standard), a funnel that fits the opening, and a water source. If you have another working well, a municipal water tap, or stored rainwater, any of these will work. You do not need treated water; plain water from any source is fine for priming. Have a rag or old towel nearby to catch spills and wipe the area dry afterward.
Make sure the pump is switched off and will stay off while you work. If the pump has a pressure tank, check the gauge to confirm the system is not pressurized. If it reads above zero, open a faucet downstream to release pressure before you open the pump housing.
Fill the Pump Chamber Step by Step
Remove the priming plug or cap by turning it counterclockwise by hand or with a wrench, depending on the type. Set it aside in a safe place where you will not lose it. Place the funnel in the opening—if you do not have a funnel, roll a piece of cardboard into a cone shape and tape it, or straightforward pour slowly and carefully to avoid splashing.
Pour water from your bucket into the funnel in a steady stream. Watch the water level inside the pump housing rise. Keep pouring until water begins to come out of the pump's discharge pipe (the outlet where water normally flows when the pump runs). This is the sign that the chamber and the suction line are now full of water and the air has been pushed out.
Once water flows from the discharge pipe, stop pouring. Quickly replace the priming plug or cap and tighten it by hand first, then with a wrench if needed—snug but not so tight that you strip the threads. Wipe away any spilled water with your rag.
Start the Pump and Confirm the Prime Held
Turn on the pump when ready after replacing the plug. The pump should begin to pull water from the well within 10 to 30 seconds. You will hear a change in the pump's sound—usually a quieter, smoother hum instead of a grinding or laboring noise—and water should flow from the discharge pipe or into your pressure tank.
If water flows right away, the prime was successful. Let the pump run for a minute or two to confirm steady flow, then turn it off and check for any leaks around the priming plug or other connections. A small drip is normal; a steady stream means you need to tighten the plug or check for a cracked fitting.
If no water comes out after 30 seconds, the prime was lost. This usually means air re-entered the suction line through a leak. Turn off the pump, wait a minute, and repeat the priming process. If you have to prime more than twice, see the troubleshooting section below.
Common Mistakes That Lose the Prime
The most frequent error is waiting too long between priming and starting the pump. If you prime and then walk away for five minutes, air can seep back in through tiny leaks in the suction line. Prime and start the pump within 30 seconds of replacing the plug.
Another mistake is not filling the pump completely. If you stop pouring before water comes out the discharge pipe, the suction line is still full of air. Keep pouring until you see water flow from the outlet, even if it seems like a lot of water going in.
Loose connections also break the prime. Check that the suction line (the pipe running from the well to the pump) is hand-tight at both ends. A connection that looks tight may still have a hairline gap that lets air in. If the pump loses prime repeatedly, tighten every fitting on the suction side of the pump.
What to Do If the Pump Will Not Hold Prime
If the pump loses prime when ready after you start it, or if you have primed it three or more times without success, the problem is not the priming method—it is a leak or a stuck valve. Check the entire suction line (from the well to the pump) for cracks, loose fittings, or holes. Even a pinhole leak will let air in and break the prime.
Look for water dripping or pooling around any connection on the suction side. Tighten fittings with a wrench, working from the well toward the pump. If tightening does not stop the leak, the fitting may need to be disassembled, cleaned, and reassembled with fresh thread seal tape or plumber's putty.
A stuck check valve (a one-way valve in the suction line that prevents backflow) can also prevent priming. If you have a check valve and the pump will not prime, the valve may be stuck closed. This requires opening the suction line and inspecting or replacing the valve—a task that usually needs a plumber if you are not familiar with your system.
Priming After Repairs or Seasonal Shutdown
If you have drained the system for repairs or the pump has sat unused for weeks, the suction line will be full of air. The priming process is the same: fill the pump chamber until water comes out the discharge pipe, replace the plug, and start the pump when ready. You may need to prime twice if the line is very long (over 50 feet).
For seasonal systems or pumps that sit idle, keep a bucket of water nearby during the first startup. If the pump does not produce water within a minute, you can prime again without having to fetch water from elsewhere. Some owners keep a small tank of water next to the pump for this reason.
Frequently Asked Questions
Can I use any water to prime the pump?
Yes. Tap water, well water, rainwater, or even pond water will work for priming. The water is only filling the chamber temporarily; it does not go into your storage or supply. Once the pump starts, it will pull fresh water from the well and push out whatever you used to prime.
What if water does not come out the discharge pipe when I pour?
Keep pouring. The suction line may be long or the pump chamber larger than you expect. Pour until you see water flowing from the outlet, even if it takes a full bucket. If you have poured an entire bucket and still see no water, stop and check that you are pouring into the correct opening and that the discharge pipe is not blocked or kinked.
How long can a primed pump sit before I have to start it?
Start the pump within 30 seconds of replacing the priming plug. The longer you wait, the more likely air will seep back in through small leaks. If you must wait longer, re-prime before starting.
Do I need to prime the pump every time I turn it on?
No. Once the pump is primed and running, it stays primed as long as the system stays full of water and there are no leaks. You only prime after the system has been drained, the pump has run dry, or you have opened the suction line for repairs.
What does it mean if the pump makes a grinding noise after I prime it?
A grinding or squealing sound usually means the pump is cavitating—running with air bubbles in the chamber. This happens when the prime was incomplete or air is leaking in. Turn off the pump, wait a minute, and prime again, making sure water flows from the discharge pipe before you start.