Priming fills the pump and intake line with water so it can create suction
Priming means filling your pump casing and the pipe that runs down into the well with water before you start it. A deep well pump cannot pull water up from below on its own—it needs water already inside the system to create the seal and suction that draws more water up. If air gets into the line (from a leak, a repair, or sitting unused), the pump will run but produce no water. Priming puts the water back.
The method depends on whether your pump is a jet pump (the most common type for wells 25 to 100 feet deep) or a submersible pump (which sits underwater). Both need priming, but you access them differently. A jet pump sits above ground near the well, so you can reach it easily. A submersible pump is down in the well, so priming is usually a job for the pump installer or a well service company.
Key Takeaways
- A pump loses its prime when air enters the casing or intake line, and it will run without producing water until you refill it.
- Jet pumps (above-ground) can often be primed by pouring water into the priming plug or priming port on top of the pump casing.
- Submersible pumps (underwater) usually need a professional to reprime because the pump is inside the well and harder to access.
- After priming, run the pump for a few minutes to push out any remaining air and restore full water pressure.
- If a pump loses prime repeatedly, the problem is usually a leak in the intake line or a failed check valve, not the priming itself.
How to Prime a Jet Pump Above Ground
Locate the priming plug or priming port on the top of your pump casing. It is usually a small brass or plastic cap, often labeled "Prime" or marked with an arrow. On some models it sits next to the pressure gauge. Unscrew it by hand or with a wrench—it should come loose without much force.
Fill a bucket with water from a working faucet or hose. Pour water slowly into the opening until it reaches the top and begins to overflow slightly. This fills the pump casing and the intake line below. Screw the priming plug back in firmly but do not overtighten it, which can crack the fitting.
Turn on the pump and let it run for two to three minutes. You may hear air hissing or sputtering at first—that is normal. Once the sound stops and water flows steadily from your faucet or outdoor tap, the pump is primed and working. If water does not appear after five minutes, turn the pump off, wait a minute, and repeat the priming step.
Priming a Submersible Pump Requires Professional Help
Submersible pumps sit at the bottom of the well inside a steel casing. There is no priming plug you can reach from above, and opening the well casing yourself risks contaminating the water supply. If a submersible pump loses prime, the pump installer or a licensed well service company should handle it.
The technician will either pull the pump to the surface and reprime it, or use a specialized priming procedure that forces water down the discharge line to refill the pump underwater. This usually costs between $150 and $300 depending on how deep the well is and how long the repair takes. If your pump is still under warranty, contact the installer first—they may cover the cost.
Why Pumps Lose Prime and How to Stop It Happening Again
A pump loses prime when air enters the system. The most common causes are a leak in the intake line (the pipe running from the pump down into the well), a cracked fitting at the pump, or a failed check valve (a one-way valve that prevents water from flowing backward). If your pump loses prime once, it was probably a one-time air pocket. If it happens repeatedly, there is a leak somewhere.
Inspect the intake line where it connects to the pump for wet spots or drips. Check the priming plug area for moisture. If you see water, the fitting is leaking and needs to be tightened or replaced. If the line looks dry but the pump keeps losing prime, the check valve inside the pump may have failed—that is a job for a technician, because the pump will need to be opened or replaced.
Keep the area around your pump clean and dry. If the pump sits in a basement or crawlspace, make sure there are no puddles or standing water that could indicate a slow leak. A small leak now becomes a big problem later.
When to Call a Well Service Professional
Call a professional if priming does not restore water pressure, if the pump loses prime within a few days of priming, or if you see water leaking from the pump casing or fittings. You should also call if your pump is a submersible model, because you cannot safely access it yourself.
A well service company can pressure-test the intake line to find leaks, replace a failed check valve, or pull and service a submersible pump. They can also tell you whether the problem is the pump itself or something in the well—sometimes sediment or a collapsed intake screen causes the same symptoms as a lost prime. Getting a professional diagnosis now saves you from guessing and wasting time.
Priming Tools and Materials You May Need
For a jet pump, you need a bucket, a source of clean water, and possibly a wrench if the priming plug is stuck. Some people keep a hand pump or a small electric pump nearby so they can prime without running to a faucet, but this is optional. If you are priming after a repair, make sure the technician has not left any air in the line—ask them to run the pump before they leave.
Do not use well water from a bucket if the well has been contaminated or if you are unsure of the water quality. Use tap water from a municipal supply or a known clean source. This prevents bacteria or sediment from entering the pump during priming.
Frequently Asked Questions
How long does it take to prime a pump?
Pouring water into the priming port takes about two minutes. Running the pump to clear air takes another two to five minutes. Total time is usually under ten minutes. If it takes longer than that, turn off the pump and check for a leak in the intake line.
Can I prime a pump if the well is dry?
No. Priming only works if there is water in the well to draw up. If your well has run dry, you cannot prime the pump—the pump will just run without producing water. You will need a well service company to diagnose why the well is dry and whether it can be recovered.
What if water comes out of the priming plug when I unscrew it?
That is a good sign—it means the pump still has water in it and may not need priming. Screw the plug back in and turn on the pump. If water comes out of your faucets, the pump is working. If not, follow the priming steps anyway.
Do I need to prime my pump every time I turn it on?
No. Once primed, a pump stays primed as long as there are no leaks. You should only need to prime after a repair, after the pump has sat unused for months, or if a leak has let air into the line. If you are priming more than once a year, there is likely a leak that needs to be found and fixed.
Can I use a garden hose to prime instead of pouring from a bucket?
Yes, if the hose reaches the priming port. Attach the hose and run water slowly into the opening until it overflows. This is faster than bucket-filling and works just as well. Make sure the water source is clean—do not use water from a hose that has been sitting in the sun for weeks, as it may contain bacteria.