The pump is running. The kitchen tap spits air and quits. On a jet pump, that combination almost always means one thing: the pump has lost its prime and is spinning against air instead of water.
Knowing how to prime a well pump costs you twenty minutes and a five gallon bucket of clean water. Knowing when to stop trying is worth more. A jet pump left running dry will burn its mechanical seal, then scour its impeller, and a replacement runs $800 to $2,000 installed in the Wenatchee Valley.
This guide covers the three situations we see most often. A shallow well jet pump that lost prime overnight. A deep well two pipe jet that needs both lines charged. And a cabin pump that sat all winter and now will not catch no matter how much water you pour in it.
What Priming Actually Does, and Which Pumps Need It
A jet pump sits above ground, usually in a pump house, a crawlspace or a utility room, and pulls water out of the well by suction. Suction only works on liquid. Air compresses, so an impeller spinning in air makes noise and heat and moves nothing.
Priming means filling the pump housing and the suction pipe with water so the impeller has something solid to grab. Once it grabs, the pump creates the vacuum that lifts the rest of the water column behind it.
Here is the part that saves people a wasted Saturday. Submersible pumps never need priming. A submersible sits down in the well, permanently underwater, often two or three hundred feet below your boots. If that is what you have, priming is not on the list at all. Our guide to submersible versus jet pumps shows how to tell them apart in about a minute. The quick test: if your pump house holds only a pressure tank, a pressure switch and some pipe, with no motor bolted to the floor, your pump is down the well and this article does not apply to you.
Suction also has a hard physical ceiling. At our elevations a single pipe shallow well jet can lift water roughly 20 to 25 feet and no further. Static water deeper than that needs a two pipe deep well jet or a submersible, no matter how well you prime it.
If you are not certain which pump you have, call before you start pouring water into things. (509) 300-5151 is answered around the clock, and talking it through costs nothing. Estimates are free.
Before You Prime: Five Minutes That Can Save the Pump
Priming a pump that has a different problem just wastes water and cooks the seal further. Run these checks first.
Kill the breaker. You are going to be opening a plug on a machine wired for 240 volts, often in a damp building. Switch off the pump circuit at the panel and leave it off until the fill is done.
Touch the pump body. If the casing is too hot to keep your hand on, it has been running dry for a while. Let it cool completely before you add cold water. Cold water into a hot cast iron housing can crack it.
Read the pressure gauge. Zero means the system is empty. A gauge sitting at 40 or 50 psi while no water reaches the house points somewhere else, usually a closed valve, a frozen line or a fault past the tank. Our article on no water from the well all of a sudden walks through that fork in the road.
Look for water on the ground. A wet patch near the wellhead, a dripping pitless adapter or a weeping fitting tells you where your prime went. Priming will not hold until that is fixed.
Ask what changed. A power outage, a hard freeze, a well that got pumped down during irrigation season, a new filter housing installed last week. The event usually names the cause.
How to Prime a Shallow Well Jet Pump, Step by Step
This is the single pipe setup: one suction line running from the pump down into the well or a shallow point.
- Turn off the pump breaker.
- Close the valve between the pump and the house if you have one, or close the main shutoff. This keeps you from pushing air through the house lines.
- Find the priming plug on top of the pump housing. It is usually a square headed or hex plug, sometimes marked, sometimes not. There may be a second plug on the discharge side.
- Remove the plug with a wrench. Do not use pliers on it. These plugs round off easily and then you have a second problem.
- Fill the housing with clean water. Use potable water, not ditch or irrigation water. Pour slowly so air can escape. Keep filling until water sits right at the top of the opening and stops going down.
- Wait. Water is running down the suction pipe to fill it. Top it up two or three more times over five minutes until the level stops dropping.
- Reinstall the plug with a wrap of thread tape and snug it. Snug, not gorilla tight.
- Open the valve to the house, turn the breaker on, and watch the pressure gauge. You want to see the needle climbing within thirty to sixty seconds.
If the gauge climbs and holds, you are done. Run a hose bib for a few minutes to clear air out of the lines.
If the gauge does not move at all after two minutes, shut it off. Do not let it keep spinning. Repeat the fill once. If the second attempt fails, the pump is telling you something and more water will not change the answer.
A 1990s manufactured home on the flats outside East Wenatchee came in as a no water call last spring. Shallow well, static level about 18 feet, single pipe jet in a plywood pump house. The homeowner had primed it four times and it caught every time, then died again by morning. The pump was fine. The foot valve at the bottom of the suction line had a pinhole and drained the pipe back into the well overnight. Diagnosis was $195 on our service call range of $150 to $250, and that amount came off the repair when they hired us.
Priming a Deep Well Jet Pump: Two Pipes, One Extra Problem
A deep well jet has two pipes going into the well, a larger suction line and a smaller pressure line. The pump pushes water down the small pipe through a jet assembly at depth, which creates the lift.
The priming procedure is the same in principle, with one difference that trips people up. Both pipes and the jet body downhole have to be full. That takes much more water and much more patience than a shallow setup, sometimes ten to fifteen gallons and several rounds of topping up.
There is usually a control valve on the pressure side. On many units you throttle it partly closed while the system builds, then open it slowly once the gauge reaches operating pressure. Not every model works this way. Find the make and model tag on the motor and check the manufacturer’s instructions before you start turning valves.
If the system has an air volume control or a check valve on the suction line, air can be trapped where you cannot reach it. That is the point where a homeowner attempt honestly stops being economical. A tech with a vacuum gauge finds a suction side leak in fifteen minutes that can take a weekend to chase by trial and error.
How to Prime a Well Pump After It Sat All Winter
Seasonal cabins are their own category. A pump that sat from October to April has three failure modes stacked on top of each other, and priming addresses only one of them.
Start by looking for freeze damage before you add any water. Check the pump housing for hairline cracks, especially on the underside where water pools. Check the pressure tank, the switch tube, the gauge and every plastic fitting. Cast iron that froze full of water often does not leak until it is under pressure, and then it sprays.
Next, do not just flip the breaker. Fill the system, then start the pump and stand there. Listen for a smooth rise in the gauge. Grinding, screeching or a smell of hot varnish means shut it down.
Third, plan on treating the water. A system that sat idle for months can grow bacteria in the lines and the tank. The Washington State Department of Health has guidance for private well owners on testing and disinfection, and our piece on seasonal cabin well startup and shutdown covers the order of operations.
A cabin above Leavenworth that got left unheated over Christmas is the clean example. The owner primed it in March, it caught, built to 50 psi, and then a hairline crack in the jet pump casing opened under pressure and emptied the housing across the floor. The pump was not repairable. Replacement landed in the $800 to $2,000 jet pump range, and it would have been avoided by draining the housing in the fall.
When the Prime Will Not Hold: What the Pump Is Telling You
How the system behaves after you prime it is the diagnosis. Match your symptom to this table.
| What happens after you prime | Most likely cause | What it takes to fix | Typical cost |
|---|---|---|---|
| Catches, holds, still fine tomorrow | Air pocket or a power blip, nothing broken | Nothing | $0 |
| Works all day, empty again by morning | Foot valve or check valve leaking back down the well | Replace the valve, pressure test the line | Service call $150 to $250, repair commonly $300 to $1,200 |
| Loses prime within minutes | Air leak on the suction side, usually a fitting or cracked pipe above ground | Locate with a vacuum gauge and seal | $150 to $250 diagnosis, parts and labor on top |
| Never catches, motor runs smoothly | Water level below suction limit, plugged foot valve, or a worn impeller | Wellhead diagnosis, possible pump work | $150 to $250 diagnosis, applied to the repair |
| Motor hums but will not spin | Start capacitor or control box, not a priming problem at all | Capacitor or control box | $200 to $450 |
| Primes fine, then snaps on and off rapidly | Waterlogged pressure tank or a failing pressure switch | Tank or switch replacement | Switch $150 to $350, tank $600 to $1,800 |
Two notes on parts. A foot valve itself is roughly a $20 to $60 item at a local supply house, which is a general parts estimate and not a quote. What it costs to reach one depends entirely on whether the suction line is exposed in a pump house or buried under a driveway.
And the most common wrong turn we get called about: an orchard house above Cashmere running a submersible and a 44 gallon bladder tank. The owner spent an evening looking for a priming plug that does not exist on that system. The actual fault was a pressure switch with sediment in the tube, which falls in the $150 to $350 range. Half an hour of work once someone looked at the right component.
If your prime will not hold after two honest attempts, stop cycling the pump. Every dry start costs seal life. Book a well pump repair and we will bring a vacuum gauge and find it properly. If the house is out of water today, that is what 24/7 emergency well service is for. After hours work carries a premium of $150 to $300 on top of the repair, and we will tell you on the phone whether waiting until morning is the smarter call.
Three ground rules while you work. Prime with clean potable water only, because whatever goes in the housing ends up in your plumbing. Never let a dry jet pump spin to see if it catches: thirty seconds is a test, five minutes is damage. And leave the pressure switch cover closed, since that enclosure carries live 240 volt terminals and is not a homeowner component.
One last thing. If the well has been sluggish all summer, priming is treating a symptom. A low static water level is a well problem, not a pump problem, and the EPA’s private well resources are a fair starting point on what affects yield. We work across Chelan, Douglas and Grant counties, and estimates are free either way. Reach us here.
Frequently Asked Questions
How long does it take to prime a well pump?
A shallow well jet pump usually takes fifteen to twenty minutes including the top ups, and it should build pressure within a minute of starting. A deep well two pipe system takes longer, often thirty to forty five minutes, because both pipes and the downhole jet have to fill. If you are past an hour and it still will not catch, the problem is not the prime.
Can I prime a well pump with a garden hose?
Yes, if the hose is connected to a clean potable supply such as a neighbor’s house or a water tank, and you let it run through first to flush out anything sitting in the hose. Do not prime with irrigation or ditch water. Whatever goes in the pump housing travels straight into your household plumbing and, on some systems, back down the well.
Why does my well pump lose prime overnight but work fine during the day?
That pattern almost always points to a leaking foot valve or check valve. While you are using water the pump keeps the line full, but overnight the column drains back into the well and the pump wakes up dry. The fix is a valve replacement, and it usually falls in the $300 to $1,200 range depending on how the suction line is run.
Can trying to prime a pump damage it?
Filling it correctly cannot hurt anything. Repeated dry starts can. Each time the impeller spins without water it heats the mechanical seal, and once that seal hardens it leaks permanently. Two failed attempts is a reasonable limit before you call someone with a vacuum gauge.