How to Manually Reprime a Well Pump After an Extended Power Outage
The power is back, the pump runs, and nothing comes out of the tap. Or the pump hums and the pressure gauge sits at zero. If your pump has lost its prime, it is pulling air instead of water, and it will not recover on its own. Repriming is a manageable job on the right type of pump, but it needs to be done carefully and with the power off.
First: Does Your Pump Need Repriming at All?
This job applies mainly to above-ground pumps, such as jet pumps (shallow or deep well) that sit in a basement, well house, or pump house. A submersible pump sits underwater in the well and is normally already surrounded by water, so it usually does not need manual repriming. If you have a submersible and no water, look at the pressure switch, breaker, pressure tank, and any possible well or electrical issue instead, and consider calling a well professional.
Why a Pump Loses Prime
- A failed foot valve or check valve. These valves hold water in the suction line. If they leak, the line drains back and the pump loses prime.
- An air leak in the suction line. A loose fitting or cracked pipe lets air in.
- The pump ran dry. A falling water level during an outage, or a pump that cycled with no water, can break the prime.
- A drained pump casing. Sometimes the pump simply drained after sitting unused.
Safety First
Well pumps are electrical equipment working with water. Turn off the breaker for the pump before you open any prime port or touch the pump. Never run the pump dry for extended periods, because that can overheat and damage the seals and motor. If you are not comfortable with any step, call a licensed well pump professional.
How to Reprime a Jet Pump: Step by Step
- Turn off the power at the breaker and confirm the pump is off.
- Open a faucet in the house to relieve pressure and let air escape.
- Locate the prime port or plug on top of the pump housing. Check your owner’s manual if you are unsure which plug is the prime port.
- Remove the prime plug and fill the pump housing slowly with clean water until it is full and water is at the opening. A funnel makes this easier.
- Fill the suction pipe if you can reach it, since this helps recover the prime faster.
- Reinstall the plug using PTFE thread seal tape and tighten it snugly, but do not overtighten.
- Restore power and let the pump run for a minute or two, with the faucet still open, until water flows steadily and the pressure builds.
- Close the faucet once the flow is steady and watch that the pressure gauge rises to the normal range.
- If no water arrives after a few minutes, shut the pump off and repeat the fill. Do not let it run dry for long.
If It Still Will Not Prime
If the pump repeatedly loses its prime, the cause is usually an air leak or a failing foot valve rather than a one-time outage effect. Check these:
- Inspect suction-side fittings and unions for leaks, and tighten or reseal them.
- Look at any visible suction pipe for cracks.
- Consider replacing the foot valve at the bottom of the suction line, which may require a professional if it is deep in the well.
- Check that the water level in the well has not dropped below the intake.
Recommended Products
A good seal at the prime plug matters, and Oatey PTFE thread seal tape is an inexpensive, widely used choice for wrapping the threads before reinstalling the plug so you do not draw in air. #CommissionsEarned
For loosening and tightening plugs and fittings without damaging them, a RIDGID pipe wrench in a size that fits your pump’s connections gives you the leverage you need, while an adjustable wrench or tongue-and-groove pliers can handle the smaller fittings. #CommissionsEarned
If a failing foot valve or check valve is the cause of repeated prime loss, a replacement brass foot valve sized to match your suction pipe (verify the diameter and thread type first) restores the one-way flow that keeps the line full. Replacement may be easier with a professional if the valve sits deep in the well. #CommissionsEarned
Quick Troubleshooting Table
| Symptom | Likely Cause | What to Try |
|---|---|---|
| Pump runs, no water, gauge at zero | Lost prime | Reprime with water, power off first |
| Loses prime again soon after | Failed foot valve or suction leak | Inspect fittings, replace foot valve |
| Sputtering air at taps | Air in lines | Open faucets, let system purge |
| Pump hums but does not run | Electrical or motor issue | Turn off, call a professional |
| Submersible pump, no water | Not a priming issue | Check breaker, pressure switch, tank, call a pro |
Common Mistakes to Avoid
Opening the prime port with the power on. Always turn off the breaker first.
Running the pump dry. Dry running overheats seals and the motor. Stop and reprime if water does not arrive quickly.
Skipping thread tape. A poor seal lets air in and causes the pump to lose prime again.
Treating a submersible like a jet pump. Submersibles generally do not need manual priming, so look elsewhere for the fault.
Ignoring a repeat problem. If the pump keeps losing prime, find the leak or failing valve rather than refilling over and over.
FAQ
How long should it take to reprime a pump?
Often a few minutes once the casing and suction line are full of water. If it has not recovered after a few tries, there is likely an air leak or failed valve.
Can a power outage cause a pump to lose prime?
It can, especially for jet pumps with a leaking foot valve or check valve. The suction line can drain while the pump is off.
Do submersible pumps need priming?
Generally not, because they sit in the water. No water from a submersible usually points to another cause.
What kind of water should I use to prime?
Clean water is best. Avoid contaminated water, since it can end up in your plumbing.
When should I call a professional?
If the pump will not prime after repeated attempts, makes unusual noises, trips the breaker, or you suspect a failed valve deep in the well.
This article is general information, not professional plumbing or electrical advice. Always turn off power before servicing a pump and consult your owner’s manual or a licensed professional.
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