Foot valve sketch (C) Carson Dunlop Associates Repeated Loss of Well Prime
How to Diagnose & Repair Repeated Loss of Well Pump Prime

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How to prime the well pump & how to diagnose & fix repeated loss of well pump prime:

How to get the water pump working again when the problem is lost prime & What types of water pumps are most likely to need to be primed?

The spinning impeller inside of a typical jet pump requires a water-filled cavity in order to develop enough lift power to bring water up from the well. Loss of well prime means that the water inside an above-ground well pump has been lost along with water in the piping between the pump and the well

. The air-bound pump can no longer lift water out of the well. Here we describe the common causes of this water loss and thus the loss of well pump prime.

Page top sketch courtesy of Carson Dunlop Associates. The sketch shows how a foot valve works and where it is installed. Replacing a foot valve in the well requires that the well be opened and the well piping be pulled out to permit removal of the old valve and installation of a new one.

This article series describes how to prime a water pump to restore water pressure to a building.

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Recurrent Lost Prime in a Well Pump? - How to Fix Repeated Water Pressure Loss

One line jet pump water system components (C) Daniel Friedman InspectApedia.comFirst Let's Correctly Identify The Type of Water Delivery Problem You've Got

Before we get into details about how to prime the well pump, or diagnosing why the well pump keeps losing its prime, let's make sure we're tackling the correct problem. If the diagnosis determines that you need to re-prime the water pump, the instructions are provided in this article.

If you have no water pressure, absolutely no water in the building water supply piping, and no water in the water pump, we've lost prime and the one line or two line jet pump may be unable to bring water back from the well.

Of course other problems can cause loss of water pressure, but if the problem is lost prime in the well pump, below is the procedure for restoring water pressure in the building. We discuss various causes of loss of water pressure at WATER PRESSURE LOSS DIAGNOSIS & REPAIR.

But where a one line or two line jet pump is installed, you may have lost prime at the pump. The pump motor will run but no water is delivered. If this happens it is possible to re-prime the pump with water from another source.

Watch out: before proceeding, turn off electrical power to the well pump. If a jet pump is allowed to continue to run "dry" there is risk that you will damage the pump impeller assembly or the pump motor.

[Click to enlarge any image]

If your water pump is a one-line jet pump, like the system shown in our sketch above, it is sucking water from a shallow well; you probably don't want to do so yet (read more of this article first), but the instructions at WATER PUMP PRIMING PROCEDURE show how to prime the well pump and they should work equally well for either a one-line jet pump or a two line jet pump.

Details about one-line jet pumps and how they work are at WATER PUMP, ONE LINE JET.

If your water pump is a two-line jet pump (shown in our photograph below) and if it's running but there is no water delivered to the building, the problem could be that the water pump has lost its prime.

Two line jet pump  (C) Daniel FriedmanA two-line jet pump needs to send water down into the well (and through a special valve at the end of the water pickup-pipe in the well) in order to bring water back to the building.

At the bottom of the well pipe the downcoming water squirts through a venturi device to send a larger quantity of water back up the larger-diameter pipe, through the pump assembly and into the water system.

If the jet pump pump impeller assembly is filled with air it has no pumping power. Details about how 2-line jet pumps work are at WATER PUMP, TWO LINE JET.

If your water pump is a submersible unit, the pump is located down in the well itself. In this case if you have not got water pressure, the problem may be with the pump or the well itself, but it's not a loss of prime - since they are normally always under-water, submersible water pumps are self-priming.

Details about submersible well pumps are at WATER PUMP, SUBMERSIBLE but what you need to know here is that a submersible well pump won't lose prime unless the water level in the well has dropped below the level of the pump itself. If that has happened, the problem is lack of water in the well, not a pump priming problem.

If your water pump keeps losing prime repeatedly, a shallow well jet pump well line could have a bad foot valve (in the well) and so be losing prime.

A leak in the well line can also lead to loss of prime. If priming the well water pump using one of our methods shown below seems to fix the problem but soon the well pump loses prime again, your plumber will want to check for a bad foot valve in the well or a leak in the well piping between the well and the building.

If this is the case continue reading this article for diagnostic suggestions.

Check valves installed at the proper location at the pump and perhaps elsewhere can help prevent loss of prime on this system. (Other problems that can give the same symptom include internal damage to the water pump, a well that has run dry, or a piping leak between the well and the building it serves.)

Watch out: If your 2-line jet pump (or other above-ground well water pump) loses prime and cannot draw water from the well, don't let the well pump keep running as you may burn up the pump motor or damage the pump internal parts. Take the steps outlined next.

Before assuming that a water problem is due to the well itself, see WATER PUMP REPAIR GUIDE an specific case which offers an example of diagnosis of loss of water pressure, loss of water, and analyzes the actual repair cost. sterile containers).

What to Do if a Water Pump Keeps on Losing its Prime

Points of air leaks at well pipiing can cause loss of prime (C) Daniel FriedmanIf your water pump is in the building and the pump keeps losing its prime, a shallow well jet pump well line could have a bad foot valve (in the well) and so be losing prime.

A leak in the well line can also lead to loss of prime.

If priming the well water pump using one of our methods shown below seems to fix the problem but soon the well pump loses prime again, your plumber will want to check for a bad foot valve in the well or a leak in the well piping between the well and the building.

Common causes of repeated loss of well pump prime & thus loss of water pressure

For example, a leak in the well piping inside the well can permit water in the piping and well pump to siphon backwards out of the well pump (and even the water pressure tank) down into the well when the pump as stopped.

If we prime a pump and it seems to work fine but then loses prime again after sitting un-used over night or for a longer period, we'd ask our plumber to check for a foot valve problem or a leak in the well piping.

Don't aggravate your plumber: remember to listen to your plumber. If you are too "directive" in telling the plumber what to do, s/he may do exactly what you ask even though s/he has a better idea of where the problem lies.

[When I was a boy my mom Teal used to sing this song to me Don't aggravate your mother or you'll wish that you were dead. Don't aggravate your mother or she'll smack you in the head. Smacks were less frequent than the song.]

Watch out: After pulling well piping out of the well for any purpose, such as for replacing the foot valve or repairing a leak in well piping, you should shock the well and well piping since you've probably contaminated it by laying your well piping and parts on the ground.

Well piping, foot valves, tailpieces and other parts stored at the plumbing supplier are not kept in sanitary conditions either.

We explain how to shock a well

Step by Step Diagnosis of Recurrent Loss of Well Prime

FloTec Water pressure tank (C) InspectApedia GVReader Question: Trouble with new pressure tank from Flotec

5/25/2014 Reader G.V. wrote:

My water is pumped from the well in the adjoining canyon to the big, black storage tank level with the house.

Thence it is pumped into a smaller pressure tank which shoves it the house faucets and shower at an acceptable pressure. That pressure tank was the one I replaced after decades of use because its mechanism went bad.

[Click to enlarge any image]

The new one is correctly installed, fittings and connections show no water leaks yet, when the pump turns on because we have used up about 15 gallons of water in house or garden. That water is replenished without any noticeable gap in the flow.

BUT: Even though we may not use use water for a while, water is lost which makes the pump come on needlessly.

The mystery is that no water is actually lost because the level in the big storage tank is NOT lowered.

That means, the new pressure tank may be faulty in that it signals that water has been taken out of the new pressure tank but was not really used and is looped BACK into the storage tank ad infinitum unless we turn on a faucet, do a wash, shower or do dishes.

That's the best way I can explain it. Have now posted this conundrum in shorter version to a forum where I found similar complaints. Thus I suspect the new pressure tank may not respond to any water being used, causing the pump to run because the water has mysteriously drained. required.

I don't know where else to look because the pump s working fine. Of course, I can have the local plumber come and look at it but for $ 50.- , which would be wasted if in fact I would need to get another tank under the warranty.

So in the meantime, we control the pump from our breaker box in the house.

Every time that we need water, we kick the breaker on for a few minutes in the knowledge that another 15 gallons is available for about 5 minutes without the pump motor coming on because the unused portion of water has been siphoned back from the smaller pressure tank into the large storage tank.

I'll add that I have tried a possible solution by shutting down the water supply to the house, thus disconnecting the flow completely. That did not mitigate the loss of water pressure in the Flotec.

Reply: shut off house water and watch for loss of prime

Shutting off water into the house eliminates a clandestine leak such as a running toilet. (we assume for now that's shutoff valves actually shut off fully).

That's why I suggest what means is a leak in well piping or a bad check valve at the pump or a bad foot valve in the well.

Reader follow-up: should I install an additional check valve?

Craftsman 1-line jet pump check valve (C) GVThanks, Daniel.

That is the only location I have not tested. Is there a way to see if the check valve allows a back flow into the storage tank?

The Craftsman manual shows the check valve as being screwed into the pump housing but it does not have groves or "wings" to use a tool to unscrew it. Also, how could it have gone bad? Movable parts? A spring?

Would it be easier to install a one-way valve in the 1-1/4 inch intake pipe just outside the pump body?

Reply: pump check valves can fail; don't install multiple check valves

You pose an interesting question for which I don't have a good answer, though I suspect an experienced plumber might have something to say.

Check valves can fail due to wear but more often due to debris accumulation on the valve seat or on occasion mineral deposition.

I suspect that when in doubt the plumber just replaces the valve at the pump, as that's easier than testing it.

If you can get the valve off we could try (really you could try but I'm interested) inspecting it for obvious trouble, cleaning it and watching what happens.

I can't tell from your photo whether this is a 1-line or 2-line jet pump.

If you give me the pump model number we can look for its installation and service manual (or do you have it?) to see how the check valve is removed. Perhaps it unscrews using a pipe wrench (that'll leave some marks).

I am reluctant to add additional check valves without more research. Some pump systems specifically advise against multiple check valves (that can lead to operating troubles) while in other installations I see that they're in use: at the pump and of course in the well at the foot valve.

Reader follow-up: Sears Craftsman 1-Line Jet Pump Check Valve Installation Details

Craftsman 1-line jet pump check valve (C) GVHere is the info you needed on the pump's check valve.

Per Google it seems that there are "universal" check valves on the market literally for a song while the Sears one is almost $ 50.- shipped.

I had been waiting for your reply before disconnecting the pipe from the pump housing and unscrewing part 12A (circled in blue) but don't know if that will show me anything. I spent much of last night reading everything you have written about mine and other people's problems my head is spinning :-) .

I have very soft well water and use one filter at the well pump and a second one on the storage tank and a third one in the fridge for drinking water. Everything is clean and dirt clogging is not present.

The tire pressure gauge reads 38 lbs. on the new pressure tank, pump kicks in at 28 and cut-out is 44. Tell me if that is within bounds.

Yes, I read too that one should not have any more valves than one but thought that an additional one-way outside the pump would be OK since the internal (12A) doesn't seem to be doing its job. I don't mind scratching the part that my finger is indicating. It has no grooves and thus I thought it's not removable, but the schematic seems to show that it is.

And - yes - it is a ONE LINE installation, typical shallow well, since it sits right next to the water source (the well and its pump is about 200 feet away and is in perfect condition). I control it from a timed switch outside the front door. The well itself is only about 7 feet deep and sits partly in a small creek which runs about 9 months of the year. The shallow aquifer is in the bottom of a canyon.

Will await your further opinion.

Reply: Procedure for distinguishing between a water pump check valve failure and a leak in well piping or foot valve

Sorry about spinning your head (makes me think of those horrible horror movies). I would welcome any suggestions about how to make our information more clear, easy to find, navigable.

Typically the well repair company will observe loss of prime, replace the above-ground at-pump check valve, and if prime is still lost they'll next pull the well piping and replace the foot valve.

If problems persist people start looking for a leak in the well piping anywhere along its route, tackling the more accessible areas first of course.

To do some detective work on your own first try these steps:

Inspect the above-ground or at-pump check valve

You should be able to unscrew and inspect the check valve. Look for

What I've been thinking about without the thrill of a perfect solution is how one can tell the difference between a leaky check valve at the pump above ground and a leaky foot valve or a leak in well piping.

A leak in well piping sometimes can be heard if it's in the well (not if it's in the buried segment),
and sometimes gives itself away by the admission of air or debris into the water supply.
But not necessarily.

Check for water leaks out of the well piping or foot valve

Where it's troublesome to inspect the well piping entirely, which is usually the case, I might try this:

This is a bit of a crude approach but might work.

Check for air leaks into the well piping or at the water pump

Air leaks INTO the well piping can also make the pump lose prime if the leak is significant.

For example, re-using ABS water pipes and elbows can leave clandestine air leaks into the piping at those joints. I've spotted this problem by looking at the clear plastic surrounding a water filter installed at the well pump. When I see air bubbles entering the filter I know there is an air source somewhere.

I've on occasion fixed the problem by tightening hose clamps on the pipe joints and by adding a second hose clamp on either side of the joint. Plumbers don't like to re-use these connections for just this problem, but since generally we don't have lots of slack in well piping that re-use is common.

Keep me posted.

Reader follow-up:

I may have confused you by bringing up my well pump installation but it serves only to supply water to the storage tank and my problems arise from that part of my system.

The well merely fills the tank near the house and works flawlessly. Its foot valve is only 7 feet down and is unobstructed.

Thus the storage tank and the new pressure tank located together are really the source of my water since I may just as well have a water truck come to my piece of land and pump water into the large 2500 ga. tank.

... we have reliable water which for the past 35 years we have had without interruption.

So she puts up with having to flip the breaker whenever we need running water in the house. I have a line running to the garden directly from the well so in that regard we're OK but it's not filtered and is not as pressurized as water out of the tank near the house.


OK so if we are confident that there is no hidden well piping leak (which I grant as a temporary assumption) we're left with returning to the question of accurate problem diagnosis.

We are talking about intermittent well pump cycling on when you don't expect it to, and we assumed a problem with a check valve or piping because you were sure that no water was being draw from the system on the "house" side of the pump and tank.

Are we sure the well is losing prime?

Alternatively if the well pump was left running for a long time it would be no surprise if it's impeller assembly was damaged. If that occurred the pump would run but not deliver water at proper pressure.

Reader comment:

I have two pumps, but it's not the well pump we're discussing but the one next to the storage tank.

The former is far away from the latter and transports water to the storage tank with its own, separate system, which is where I have the problem.


got it

I'd double check that you can successfully fully turn off water to your building.
Then watch the pump for intermittent cycling. If it cycles on there's a leak to be found.

Step by Step Diagnosis of Repeated Loss of Water Pressure: no water in the morning traced to pump leak: fooled by bad pressure gauge

Reader Question: I have found your web site to be very good and straight forward on problems and solutions but haven't found a solution to my problem yet. Let me explain our problem.

We have a ranch in south Texas that has two storage tanks (about 3000 gals each) that feed a single pump that supplies water to the house. The house is about a 1/2 mile from the pump. The storage tanks and the pump are at about the same elevation as the house but the 2" line runs down through a valley that is roughly 75' below the house.

The pump setup is a single pump with two pressure tanks (about the size of a swimming pool filter) located on the 2" discharge line via a cross and then the 2" line runs to the house.

The pressure regulator on the pump is the same one as shown on your web site. The problem is during the day the system works just fine but every morning when we get up there is zero water at the house.

If you go down to the pump and look at the pressure gauge it is reading right at 41 psi.

The regulator is set to come on right at that pressure and go off at ~51 psi. Don't really understand why this is happening. When you open the valve at the house that should relieve the pressure on the line unless the head pressure is to great to allow the pump to come on?

This same system has worked great in the past but has developed this problem. We have changed the regulator out a couple of times thinking that was the problem but it wasn't. I just today changed the set pressure so the pump to where it comes on around 48 psi and shuts off at 60 psi. If you have any ideas I sure would like to know. - C.D. 8/4/2014

Reply: is the pressure control switch accurately sensing tank pressure? Is the pressure gauge working?

When you changed the pressure control switch, did you check for evidence of debris in the water supply that might have clogged the switch sensor port or the tube that conducts the water pressure to the bottom of the pressure switch?

When you go down to the pump in the AM when there is no water pressure at the house, if you "tap" on the switch box itself will that turn on the pump?

[I asked these questions because it doesn't add-up for there to be good pressure at the water tank but no pressure in the building unless there is a blockage or total loss of connection between the pressure tank and the building - Ed. ]

Reader follow-up:

There was nothing in the line looked clean. Haven't tried tapping on the switch to see if that would kick the pump on. Always just manually close contacts.

Reply: check for a pump control that is shutting off the pump due to no water from the well

Also, some controls include a circuit that shuts off the pump if the well is running low.

But probably diagnostic is that you see water pressure in the pressure tank -

If this is an internal bladder tank, its possible that the bladder is burst and sticking to itself or not letting water in the tank or out of it. OTOH if you see tank pressure varying then I'm wrong in that guess. IF the gauge is on the tank that'd tell us something.

[The "due to no water in the well" was a clue here. I should have added "due to lost prime" - Ed. ]

Reader Follow-up: the well is not running out of water

We can't have a well running low problem because we have two big storage tanks ~6000 gals the pump is feed from. A complete separate pump system is filling the storage tanks. I can't answer the question about pressure on the pressure tanks because we don't have a gauge on them.

But to test the system we have a block valve just down stream of the pressure tanks before the line heads to the house and in the discharge line we have a 3/4 hose bib.

So all I have to do to test the pressure tanks is close the block valve and use the hose bib to bleed water of the pressure tanks and they seen to have plenty of pressure. If that makes sense to you.- C.D.


OK so we see how confused I can get by e-text.

Yes the bleed-to-confirm water pressure makes sense. IF you are getting water out of the tanks they're not blocked.

Besides for large tanks such as yours there would not be an internal bladder design. But you might encounter such a problem if you had a pump and bladder type pressure tank at the house end of the system.

Reader follow-up:

Water at house is only going through a water softener. So there are no bladders there.

Reply: look for a leak somewhere in the water system


or there is a leak

[I was thinking of a leak in the well piping, but I should have considered a leaky foot valve (loss of prime) or a leak elsewhere - Ed.]

Reader follow-up: checking water pressure, checking pressure gauge

I will let you know if raising the pressure has any effect on the problem. If the water pressure is off at the house the ranch foreman will check the gage to see if there is pressure and then he is going to open the hose bib and see if the pump comes on then.

Thanks for trying to help me fix this problem.

Reader follow-up: found leak in well pump body & a faulty pressure gauge

I believe we have determined the problem or in this case a couple of problems. What we found was the pump case actually had a small crack that during periods of none use (overnight) would allow the pump case to drain and then the pump would lose prime.

The system has a sensor on the pump to shutoff the pump in case the pump looses prime so that was why the pump would appear not to start only after sitting overnight.

Also the pressure gage was faulty and would not read less than 41 lbs, oddly enough that was the pressure where the pump should have started. So all those problems together was making it appear to be something else and that kept us looking in the wrong places.

We can sleep tonight :-) and again thanks for helping me try to figure out the problem and yes we did learn something.

Reply: pressure gauges: false friends?

That bad gauge threw us off the scent.

I'm was also confused that you said you opened a valve at the storage tanks and had plenty of water, BUT depending on the tank and piping arrangement, that might be true at those storage tanks even when water pressure in the tanks was not sufficient to push water uphill to the point of use.

Repeated Loss of water pressure: lessons learned about gauges, pumps, leaks, and well pump prime


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