Pump/pressure tank detective needed

[ngermain]

Hey guys,

My dad and I have a perplexing water problem that we can't reason out. Hoping there's some detective out there...

We have a shallow well and a jet pump, about 20m head to the house, a pressure tank and pressure switch in the house. System had been working great for 15+ years (same pump and tank too!), pressure switch is set from 30-45psi.

Here's the problem: Starting with a full pressure tank, we turn on some taps, water flows at a good pressure, the pressure gauge needle falls slowly as is expected. When the water pressure gets down to 30, the pressure switch makes an audible click but then instead of water rushing in and pressure going back up, the pressure falls fast to about 10psi and continues to trickle out the taps for hours. The pressure does not go up until we turn off all the taps. Once this is done, the pressure goes up fast again to 45psi and the cycle repeats.

??

The pump seems strong since it can pressure up fast to 45. The pressure switch (which we replaced brand new with no effect) is clicking at the right times.

Why would pressure fall fast at 30psi after the switch clicks? Why would the pump only start back up when all the taps are closed?

Any suggestions would very appreciated!!
Thanks

 

[beenthere]

:welcome:

Admit that I do not know exactly, but I would suspect there is a valve flap that is hanging open. Maybe there is a schematic of your system showing the valves that open and close that would be a lead (whether it is a valve or not).

 

[ngermain]

Thanks for the quick reply!

Valves? The only valve I can think of in the system would be the foot valve in the pump. It's a pretty simple system.

Shallow well --> pump --> buried water line --> pressure tank --> supplies house

 

[justwater]

what size is the tank? i assume this is a simple shallow well jet pump with one pipe going into the suction and one going out to the tank? what size diameter is the well? saying foot valve makes me assume it is 2" or larger? foot valves arent in the pump, they are at the bottom of a drop pipe. maybe you mean an in-line check valve at the front of the pump?

continues to trickle at how many taps after pressure falls? see how much water this is at one tap. sounds like you arent producing very much water or are either trying to run too much at once. going down fast below 30 is normal as your tank precharge (if you have bladder/diaphragm style) should have 2-5 psi less than the pressure switch cut-in setting.. so it goes from tank precharge to nothing in a hurry when demand is more than pump/well can produce.

 

[firedog]

Where are you reading the pressure? At the pump discharge or the pressure tank?
Things to consider:
*Worn impellers
*collapsed well casing
*foot valve sticking
*also check flow thru tubing to pressure switch (often becomes plugged
but does not cause the problems your seeing).

What is the discharge pressure of the pump when deadheaded?
How often does the pump cycle on/off?
Can you bypass the pressure tank and free flow the pump? If so, how much does it flow in one minute?

 

[ngermain]

Tank is about 4' high by 2.5' diameter. The pump is about 3' long, it is completely submerged in the well. Only 1 pipe on the pump and that is the output to the pressure tank. The pump input is just the other end of the pump. There is nothing inline between the pump and the tank. There must be something to stop water from flowing out the pump though and I'm pretty sure there is some sort of built-in valve in the pump. Tank does have a diaphragm.

"continues to trickle at how many taps after pressure falls?" don't understand. How many taps are on during this test? Doesn't seem to matter, 3 or 4. The system could easily support this a few days ago, we had many sprinklers running continuously.

 

[firedog]

OK, a submerged pump. That eliminates a few things.
I would be inclined to believe a restriction at the pump suction screen or some pluggage in the discharge line.
Which of course means you would have to pull the pump up out of the well.

 

[justwater]

then you definitely dont have a jet pump, you have a submersible pump. if the well was low producing with this type of pump, air would be coming out of the faucets.

what is the pump hanging on? is it pvc?, galvanized pipe?, poly pipe?

maybe a plugged screen on the pump... 45 is nothing for most subs, does the system leak down and pump kick back on even when there is no water running?

 

[ngermain]

Where are you reading the pressure? At the pump discharge or the pressure tank?
At the pressure tank, right by the pressure switch

Things to consider:
*Worn impellers
*collapsed well casing Can't be, open spring capture type "well", 12' diameter, we can stick a ladder down and check things
*foot valve sticking Don't understand how this can cause this, can you explain please? sticking open or closed?
*also check flow thru tubing to pressure switch (often becomes plugged
but does not cause the problems your seeing).

What is the discharge pressure of the pump when deadheaded?This will be difficult to measure, probably due this in a latter resort...We would have to splice into the line in the well and put a gauge on it? or measure it in the house before the tank?

How often does the pump cycle on/off? It does not cycle. Pressure drops and stays low until you shut off all taps, then it climbs fast. So if we left it, it would not cycle at all. It takes about 5-15min to drain the tank depending on # of taps open

Can you bypass the pressure tank and free flow the pump? If so, how much does it flow in one minute? This would require some work, definitely something we'll do if we can't find anything else wrong


What I don't get is why the pressure can ramp up nice and fast up to 45psi when everything is closed if the pump is dead/dying. Is it much easier to pressure up the tank and the whole system when all taps are closed than it is to pump directly into the system with taps open?

 

[Egon]

Have you checked the static and pumping water level in the well?

If water levels are good it might be time to pull the pump and see what it looks like.

 

[justwater]

yes its easier to fill the system when taps are closed rather than open, being as there is no water going anywhere

foot valves are out of the question, not applicable with this type of pump.

5-15 minutes to drain the tank?? you must not be running very much water. the tank you described shouldnt have more than a 7-10 gallon drawdown storage capacity.

 

[ngermain]

then you definitely dont have a jet pump, you have a submersible pumpSorry, don't know my pump terminology well

what is the pump hanging on? is it pvc?, galvanized pipe?, poly pipe?It's weight is suspended by a rope, hanging it in the water. The output pipe is black water pipe, PVC I imagine


maybe a plugged screen on the pump... 45 is nothing for most subs, does the system leak down and pump kick back on even when there is no water running?Yes! When everything is closed, it leaks down in about 45min. Need to check if it kicks in by itself in this case...(I'm not actually at home on the farm right now, in the city and getting panicked phone calls from dad



OK, a submerged pump. That eliminates a few things.
I would be inclined to believe a restriction at the pump suction screen or some pluggage in the discharge line.
Which of course means you would have to pull the pump up out of the well.That's not actually very difficult. 1/2h job. I'll tell dad to pull it tomorrow and have a look see.

 

[ngermain]

foot valves are out of the question, not applicable with this type of pump.Water simply doesn't flow backwards through them?



Ok, we'll pull the beast tomorrow and check its intake (and well water levels). Could it also then be any restriction in the output from pump to tank?

 

[justwater]

foot valves are used with jet pumps, you have a submersible pump.

there could be an inline check valve, but it may just be the check valve inside the pump (which is best). curious to hear what you find when you pull it. make sure you arent losing water anywhere else before pulling it

 

[CurlyDave]

Tank is about 4' high by 2.5' diameter. The pump is about 3' long, it is completely submerged in the well. Only 1 pipe on the pump and that is the output to the pressure tank. The pump input is just the other end of the pump. There is nothing inline between the pump and the tank. There must be something to stop water from flowing out the pump though and I'm pretty sure there is some sort of built-in valve in the pump. Tank does have a diaphragm.

"continues to trickle at how many taps after pressure falls?" don't understand. How many taps are on during this test? Doesn't seem to matter, 3 or 4. The system could easily support this a few days ago, we had many sprinklers running continuously.

You may have what is called a deep-well jet pump. In addition to the jet pump at the bottom of the well, there is also an electric pump on the surface, which pushes high pressure/high velocity water down the well to the jet assembly. The jet assembly looks sort of like a mutant trumpet and is at the bottom of the well. (In the world of jet pumps, anything over ~25 feet is a deep well. Your 20 m is roughly 65 feet.)

If this is what you have, there really is a second line which carries water down the well. It may be concentric with the output line and look like only one line, but there are two.

I think the problem lies in either your electric pump, the motor, or the motor starter for it.

For a general idea of how this works see: Water Well Pumps and Systems - How a Water Well Pump Works - Popular Mechanics

I think you have what they call a double drop jet pump.

Fortunately, the electric motor, the pump and the motor starter are all on the surface and are easy to access.

The least expensive route may be to disconnect the electric pump from the system and take it into a pump shop for testing.

OTOH, since the pump is at least 15 years old, you will probably find that it needs replacement and it is possible that you can avoid the cost of testing the old pump by just replacing it.

* * * * *


The way to tell if you have a submersible pump is to look and see if there are electric wires going to the pump at the bottom of the well. If there are, it is a submersible. If there are not, it is a double drop jet pump.

 

[ngermain]

definitely a submersible then, the wires connect to the pump which is under water. it's a shallow well I can stand in and grab the pump, very easy to work with.

Dad went down there yesterday and everything looks good in the well, nothing clogging the intake, good water level, no obvious leaks.

I guess we'll try reducing the tank precharge as someone suggested and try to find another pump to swap in to test if it is just a failing pump that can't pressure up unless everything's closed.

Thanks for all your help guys! will update as the situation progresses...

 

[Egon]

foot valves are used with jet pumps, you have a submersible pump.

The chances are very good that the submersible will have a valve right next to the pump either above or below depending on design that will prevent back flow.

 

[boomer1025]

The chances are very good that the submersible will have a valve right next to the pump either above or below depending on design that will prevent back flow.

Check the voltage going to the pump