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Small Cabin Forum / Cabin Construction / Jet Pump Loses Pressure when tap is turned on
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zoodlemaker
Member
# Posted: 7 Oct 2012 15:27
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Hi there, I'm having some problems with my cottage jet pump.

The pump is new, 1/2 hp shallow well pump, that is fed by a lake, 100 feet away with a 30 foot gradual drop, and it has stopped working properly.

The pump is capable of getting the water pressure up to about 30 psi, but it doesn't shut off.

When a tap is turned on in the cottage, water comes out at normal pressure for about 5 seconds, then trickles down almost immediately to nothing. At the pressure gauge, the needle drops immediately to 0, the pump keeps going, and will finally work its way back up to 30psi....in all this time, the pump is not cycling off at all.

We have a brand new Pressure Tank (this year) as well.

Does anyone have any ideas? Much thanks!

larry
Member
# Posted: 7 Oct 2012 21:54
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sounds like the pump is running dry. how deep is the well? is the pump at the bottom of the well or at grade?

Martian
Member
# Posted: 7 Oct 2012 23:37 - Edited by: Martian
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Is there a check valve to prevent the hose from draining? It sounds like the pump is losing its prime.

BTW, you may wish to consider a pressure switch with low pressure cutoff. That will protect your pump from burning itself up running dry.

Tom

zoodlemaker
Member
# Posted: 8 Oct 2012 06:46 - Edited by: zoodlemaker
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larry and Martian, so glad for your replies! Thank you very much.

We're drawing water from a lake, and we believe water is still drawing as when we open the 'bolt' where we prime the line that runs down to the lake, that line stays primed.

The problem seems not to be with drawing water.

We've had this type of system for decades - put in a new water pump and pressure tank this summer - got the system up and running for a couple of months - and this problem just started.

The pump doesn't turn off, but keeps running - we turn on a tap, water runs at regular rate for 5 seconds, pressure drops like a rock, at the sink and the pressure gauge on the pump.

Thanks for your thoughts!

Just
Member
# Posted: 8 Oct 2012 07:17
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somthing cloging the check velve in the lake ..

zoodlemaker
Member
# Posted: 8 Oct 2012 08:14
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Just, we've wondered about that too. We've checked it, but will give it another look. The foot valve came out of its protective, submerged bucket due to windy/wavy weather. When I noticed, it was bobbing on the surface of the lake.

Since then we've left the foot valve close to shore, with rocks weighing down the line. We've had a couple more windy days, so it's possible some grit did get into the foot valve.

We're going to give it a better shake-out, maybe even detach it and give it a good flush, and try again. I'll post back with the results. Thanks!

Martian
Member
# Posted: 8 Oct 2012 08:24
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If your foot valve/check valve has a piece of grit in it, the water can bleed down the pipe. There may also be an air leak at one of the connections leading down to the lake.

Tom

zoodlemaker
Member
# Posted: 8 Oct 2012 10:51
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Martian, could a piece of grit in the foot valve prevent the valve from opening OR closing?

If the valve only opens part way, perhaps it's like the water pump trying to draw all that water up with only a small slit to suck through, making it near impossible to get up to pressure.

We're going to remove it from the pipe and give it a swish.

When the pump is turned off, there is no water coming out of the taps in the cottage at all. I'm not sure if this is normal, but I don't think so.

Alternatively, we might have a leak under the cottage, but we can't hear or see any, and it's a small cottage.

zoodlemaker
Member
# Posted: 8 Oct 2012 14:14
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Just put on a brand new foot valve and the problem is still there. The pump continues to run. When a tap is opened the pressure drops down to nothing.

zoodlemaker
Member
# Posted: 8 Oct 2012 16:59
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We're realizing the pressure tank doesn't seem to be getting any water!

The line down to the lake continues to stay primed. The pump loses a bit of prime most times when we've re-opened it.

The pump doesn't seem to be able to move any water to the cottage.

It sounds like a blockage, but I can't imagine what would have gotten into the system to cause one.

Martian
Member
# Posted: 8 Oct 2012 18:31 - Edited by: Martian
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Is the pressure switch cutting off the pump? What is your pressure guage reading when the pump shuts off? Most standard pressure switches are set to cut in at 20PSI and off at 40PSI. There is a thermal switch inside the pump that will shut it down if it runs too long. So, check to make sure it is the pressure switch that cuts off the pump and not the thermal switch.

When priming the pump, there needs to be an open faucet. Any back pressure may cause the pump prime to fail. Once the water is flowing without interruption, close the valve and let the pressure tank fill. The pressure tank should have 2# less air pressure (the valve on top) than the cut in pressure.

If you have no pressure, your pump may be bad. It happens. However, I would let the pump run with a free flow for several minutes to make sure all the air is purged from the system. If it still doesn't build pressure, get a new pump.

Tom

Anonymous
# Posted: 8 Oct 2012 18:42
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Sounds like you lost prime.I know it's a pain in the,,,but you need to get that air out and replaced it with water.

larry
Member
# Posted: 8 Oct 2012 20:19
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so i read your original post again...you say you're sucking water from thirty feet below the pump??? what is the max lift of the pump? you may be beyond the pump limit. check the max tift of the pump

zoodlemaker
Member
# Posted: 9 Oct 2012 12:16
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Martian, you're mentioning opening all the facets was what did it. We seem to have had a huge amount of air in our system.

All the new connections from installing a new pump, pressure tank and foot valve this summer were extremely loose when we checked them yesterday. I wonder if it is because we installed them on a hot day in the summer and it is now getting close to freezing at night. Does that make sense?

So we just kept opening all the taps, put some Duct Tape on one of the connections we felt wasn't getting closed off enough, and the pump not only built up proper pressure, but it turned itself off. In fact, I could start to hear water entering the pressure tank, which I don't think was happening at all before with our air bubble.

Just using the shower, the pressure started off beautifully for the first couple of minutes, then cut back to half for the rest of the shower. Perhaps we still have some air to purge.

Much thanks to all! I really, really appreciate the number of people who replied, and the speed with which you all did. Having had this system for almost 50 years, we were really scuppered by this problem.

Martian
Member
# Posted: 9 Oct 2012 20:00
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I'm glad you have it working.

About the pressure drop you experienced in the shower.......since the cutoff pressure is probably 40lbs and the cut in pressure is around 20lbs, you probably did lose about half of the initial pressure during your shower. Given your lift, and making a large assumption about the pump probably being 1/2hp , I'm thinking it is doing good to keep up.

If the suction line hasn't been replaced in 50 years, you might check it. It may be a good idea to look at the ID to see if it has silted in or corroded to the point it is restricting the supply to the pump.

Tom

zoodlemaker
Member
# Posted: 10 Oct 2012 08:28
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Well, after a couple of showers and flushing the toilet several times yesterday afternoon, we weren't using the water until last night, and not a drop of water came out of the taps, not even a hiss of air.

This morning, the pump is still primed, the line to the lake is still primed, I've duct taped every new connection I can reach, turn on the pump and nothing happens. The pump runs, but it's not shifting any water at all. Turn on the indoor taps, nothing.......

Just gave it another try, don't know what we did to change things, but on 4th try, the pump seems to be drawing water, I can hear it filling the toilet. I'm not sure that the pressure tank held any water over night, in fact I suspect it didn't or we would have had water coming out of our taps last night.

Our Pressure Tank, Pump and Foot valve are all brand new. What is the ID? Intake something?

Thanks so much!

zoodlemaker
Member
# Posted: 10 Oct 2012 08:49
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Before we got the pump to turn off on its own, so while pump was still running, the water ceased coming out through the cottage taps.

Again, not even a hiss of air.

What is it that pushes the water out the facet, the pressure tank? Could we have a defective tank?

Perhaps I purchased a pressure tank that is too small for our needs? It's a 20 gal tank. We couldn't tell how big the old one was as all information had worn off. Physically, it was possibly larger than this.

The system was working for a couple of months, then suddenly did it's first sudden pressure drop when a shower was being run.

Martian
Member
# Posted: 10 Oct 2012 08:49
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ZM, ID=inside diameter.

How do you know the entire suction line is full? All it takes before you have a problem is for the water to bleed down a couple of inches . My suggestion is to put a check valve close to the pump.

If your pump is like mine, the system pressure is felt through the pump to the foot valve when the pump shuts off; that's why I suggest a check valve close to the pump. Duct tape isn't going to seal anything for very long. I would get the system up to pressure, turn off the pump, make sure all faucets are closed, and watch the pressure guage to see if it bleeds down. If so, there is a leak which must be repaired to prevent this problem from reoccurring.

Tom

Martian
Member
# Posted: 10 Oct 2012 08:58 - Edited by: Martian
Reply 


You posted while I was typing.

Pressure is built by the pump forcing water into the tank and lines. Water cannot be compressed; therefore, without the pressure tank, the pump would run every time a faucet is opened even for just a few seconds. The size of the pressure tank only controls how much water can be drawn out before the pump cuts in. Think of it as a battery for water pressure; the larger it is, the more water it stores. But, the size of the pressure tank isn't effecting the pumping action of the pump.

You have a leak on the suction side between the foot valve and the pump. Find it, fix it, and this problem will go away.

Tom

zoodlemaker
Member
# Posted: 10 Oct 2012 10:23
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Tom, I'm so happy to hear your opinion that it's on the supply side. Getting to all plumbing under the cottage to check for a leak there would require quite a bit of digging to enlarge/deepen the area...I may even have lost a bit of sleep over that one, it's quite a tight area.

Wouldn't there be some water leaking out of the supply line that we could see? We've done a visual check, run our hands along it, and tightened all pipe clamps. The hose is all above ground, and we've pulled the foot valve out of the water and tightened it as well.

The L we have coming out of the pump to the supply hose is made of plastic. We're wondering if that's a weakness and are going to try and get a metal one.

wakeslayer
Member
# Posted: 10 Oct 2012 11:19
Reply 


This could be silly, but do you have a pressure gauge on your pressure tank? A few years ago, at my home, we had been having crappy water pressure for a bit. I brought my air compressor up to the house and added air to the tank. Problem solved. You should have a valve stem for adding air to it like a tire. Pulling uphill, perhaps it need the extra help.

zoodlemaker
Member
# Posted: 10 Oct 2012 13:28
Reply 


w, we don't have a pressure gauge on our pressure tank, but it came loaded with 28psi I think it was. And we added some before moving it into place.

wakeslayer
Member
# Posted: 10 Oct 2012 14:32
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Perhaps put a tire gauge on it and see what it says now. Just throwing ideas out there.

zoodlemaker
Member
# Posted: 10 Oct 2012 15:44
Reply 


It's a good idea, w. We've checked it with exactly that, a tire gauge, ...I guess that's what you meant in your first comment, I was thinking you were referring to a permanent sort.

You've reminded me I should check it again.

However, I think Tom might be on to something when he suggests there's a leak somewhere on our supply side, somewhere on the line...which is fortunately above ground, so easy to replace, no digging up.

The pump struggles to build pressure, then loses it slowly when the pump is turned off. We've got a new foot valve, so perhaps it's our 45-year-old water line.

Martian
Member
# Posted: 10 Oct 2012 17:58
Reply 


If the leak were on the pressure side, the pump would run sporadically, but you wouldn't lose prime. What I think is happening is the suction side is letting the pressure bleed down, and when the pump comes on to re-pressurize the system, it sucks air. You could test this theory by disconnecting the line, filling it with water, and waiting to see if the water drains down.

You might Google it, but my pump supplier told me to set the accumulator tank pressure at 2PSI less than the cut in pressure of your switch. For instance, if the switch is a 20/40, then set the tank pressure at 18PSI when the system pressure is zero.

Eventually, you will get to the bottom of this problem. There just aren't that many things that will create your situation. Take heart!

Tom

Bevis
Member
# Posted: 11 Oct 2012 13:17
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I have a coworker, who also works on pumps as a second job. I let him read this post, and he is on the same page as Martian, in that you have a problem on the supply side of your system.

Martian
Member
# Posted: 11 Oct 2012 19:19
Reply 


Thanks for the validation, Bevis.

Tom

Malamute
Member
# Posted: 12 Oct 2012 10:45 - Edited by: Malamute
Reply 


This looks like its going in the right direction. I think it's in the intake side also.

Pay attention to the air preload. You cant just add air to help anything, theres ONE setting for the pressure tank that it will function properly, 2 PSI below cut IN pressure (the lower number), with the system bled out and at neutral pressure in the water line side. If the air preload isnt set properly, the pump can cycle on/off/on/off repatedly, its hard on the pump, and the pressure tank isnt doing any good. If the air preload is changing, theres 2 possibilties, the schrader valve is bad and needs to be tightened or replaced (tire valve to check or put air in the tank), or the tank diaphram has a hole in it and is leaking water into the air chamber, the tank needs to be replaced at that point, no matter its age.

zoodlemaker
Member
# Posted: 12 Oct 2012 12:34 - Edited by: zoodlemaker
Reply 


Thanks so much everyone. I took yesterday off, and back to it today. I checked the pressure tank with a tire gauge, and it was too high. I've reduced it to 18 I hope - I bled it bit by bit, the final reading was closer to 16 than 18. I don't want to recheck as pressure is released each time.

I gave a few more tries, having to re-charge the pump each time. The first few tries the pressure got higher each time, but never rose above 25 psi.

I've now got the bottom 50' of my water line disconnected, to see if the water level in the last bit of pipe holds. In 30 minutes, the level seemed to go down perhaps 1/2", but because it's windy today, I've re-topped it and re-set my timer to see if it drops again.

This last bit of hose is definitely beaten up as it's the part that can get bashed around during a storm.

Thanks everyone.

zoodlemaker
Member
# Posted: 12 Oct 2012 14:07
Reply 


Is losing about 1/2" or less of water from the opened end of the 50' pipe over the course of an hour enough to suspect a leak that would keep the pump struggling to get to 20 psi? The hose is on a 30 degree and less hill.

Also...I'm taking all these comments in.....if a pressure tank bladder got a hole, would it be something that would happen boom, all of a sudden, dropping the water pressure down by half?...and from there after have problems with the system?

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