Possible pressure switch issue?

Discussion in 'General Plumbing Help' started by Kenyon, Nov 9, 2019.

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  1. Nov 9, 2019 #1

    Kenyon

    Kenyon

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    Hello everyone. I am a bit of a rookie when it comes to plumbing, but I can usually figure things out. That being said, I am kinda stuck here. I built a cabin and I am doing all of the plumbing myself. I am working on a budget, and my family is living in the cabin while I build it. We have been living here for about a year and a half and I finally got water ran to a kitchen sink. I am going to post a diagram of what I have done from the well pump to the sink. The problem I am having is that for some reason, a couple times a day I have to go to the well and turn on the water at the spigot for a second to get the pump to kick on. If I had to guess, I would say that the pressure switch isn't flipping, but I have adjusted the "kick on" pressure as low as it will go. I had a 1-way spring valve between the freeze proof spigot and the cabin, and thought maybe that was holding too much pressure so I removed it. That didn't help. The well is about 75' deep, and the elevation change from the pressure tank to the cabin is an additional 150' or so. Also, the 1" PEX running from the pressure tank to the cabin is about 350' long. Is it possible that the weight of the water in the pipe is putting too much pressure on the switch and not allowing it to kick on? If so, aside from adjusting the switch, what else can I do? Any help you can offer is very much appreciated!
     

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  2. Nov 9, 2019 #2

    Diehard

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    Were you actually getting water to the sink? Any pressure?

    I must be missing something here. You need 65 psi at the tank just to lift the water 150 feet up. So you need about 110+ psi at the pump just to get the pressure at the cabin close to 40 psi.

    I'm not familiar with well pumps but am familiar with hydraulics. What well pump do you have? Model? Size? etc.

    What pressure shows on that gauge when the pump shuts off?
    I'm guessing the pressure switch is fine but you should be turning it up, not down.

    And I'm assuming that when you "turn on the water at the spigot for a second to get the pump to kick on" it lowers the pressure enough at the tank to cause it to come on.
     
    Last edited: Nov 9, 2019
  3. Nov 9, 2019 #3

    Kenyon

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    The pump is a 220V, 1 HP submersible pump. I'm not sure what model it is. The water pressure at the sink is fine when it is working, but there is zero water at the sink when it is not. I agree that when I turn the spigot at the pressure tank on it must be lowering the pressure enough for the switch to flip. In fact, as soon as I turn on the water I hear the switch flip.

    I think you and I are getting our lines crossed somewhere. When I said that I turned down the pressure, I meant the bottom end. Essentially, so that the pump would kick on at a lower PSI. I also turned up the upper end so that the pump kicks off at about 65 PSI. The switch will not kick on any lower than 40PSI. I turned the set screw to as low as it will go and as soon as the pressure gauge reads 40PSI it kicks on. Thank you for taking the time to try to help.
     
  4. Nov 9, 2019 #4

    Diehard

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    Your sketch shows 35-55 psi pressure switch, which I thought was the typical 20 PSI ON/OFF points.
    So you're saying it set to come on at 40 psi and off at 65 psi. (As mentioned, 65 psi is equivalent to 150 feet elevation head of water.)

    How sure are you of that 150 feet elevation difference?
    You understand what I am saying when I say 65 psi will lift water 150 feet, right? There are other slight variables like specific gravity of water, etc. but in theory if you had exactly 65 psi at a point 150 feet below your sink, as soon as you used a small amount of water, the pressure would drop say 1 psi and you would then get nothing. And you would continue to get nothing until the pressure fell all the way to 40 psi.
    So from what I'm getting so far is that the 150 may be a little less than you think and/or the actual pressure at the tank is a bit high than 65 PSI.

    What is your pressure gauge reading at the tank when it shuts off?

    EDIT: So you may be getting the pump to come on at a lower pressure but that's not helping you to maintain the required higher pressure. It's only allowing the pump to wait until it drops all the way down to 40 psi before restarting and coming up to 65psi.

    How high are your pressure switch calibrations? could you raise it to say 60 - 80 psi or 80 - 100 psi? It sounds like you have more than enough HP to be capable of meeting higher pressures.
     
    Last edited: Nov 10, 2019
  5. Nov 10, 2019 #5

    Kenyon

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    I'm sorry. I feel a bit dumb, but I am struggling to understand the concept of how this switch thing works. If you have the time and patience, I will explain my understanding and you can tell me what I am getting wrong.

    The way I understand it is that the pump fills the pressure tank until it reaches the cut off pressure (in my case, 65 PSI). At that point, the switch shuts off the pump until the pressure in the tank drops to the cut on pressure (in my case 40 PSI). I guess what is confusing me is that the water always cuts off at 65 PSI, and when I first start using the water (after turning it on for a second at the tank) it works fine for a while. Then, eventually Inhave to go "reset" again.

    WAIT, I think I might have had an epiphany. Are you saying that the weight of the water in the line is keeping the pressure from ever getting down to 40, so I should increase the pressure at which the pump kicks on? So, maybe the reason it is working at first is because the pump is not filling the tank to 65 PSI and is pushing water up to the cabin instead of just into the tank.

    I think I am finally getting what you are saying. I did understand the concept of requiring 65 PSI to push up 150ft, but I think I was missing the point that with that pressure requirement, the tank could never drop to 40 PSI. Wow! Thank you for your patience! Sometimes things just don't filter through my brain properly

    I will turn it up and see how it goes.
     
  6. Nov 10, 2019 #6

    Diehard

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    While you're at it...What is your pressure gauge reading at the tank when it shuts off?

    Also,
    How sure are you of that 150 feet elevation difference?
     
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  7. Nov 11, 2019 #7

    FishScreener

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    A simple primer: water pressure is equals to the amount of water above it, which is referred to as static head. If you do in fact have 150-ft of static head above your pump and pressure tank, the pump house is seeing 150-ft of head at all times, which is equal to 65-psi.

    So you will get a small bit of water at the very beginning, until the pressure drop below teh static pressure in the system, at which point there is no pressure difference to move the water.

    The “spring valve” you took out is most probably a back flow valve, and you need to put it back in. It keeps all the pressure in the line from pushing back on the pump at starting.

    When you open the valve at the tank room, that is bleeding the pressure down to the cut in pressure, but that pressure is not enough to actually move water to the house, because at 150-ft (65-psi) of static head you run out of pressure to lift the water as high as the house.

    I am concerned with the whole description. That is a lot of lift. If you add the pump set depth to the system delivery height, the pump is running at around 80-90 psi, which is a lot for a 1-hp pump.

    A 1-hp pump should only be delivering less than 0.1-gpm, at the heads your describing.

    Which is why folks are asking you to confirm the 150-ft of head to the point of delivery.

    I suggest you install Google Earth, and use it to get your elevations. It is only plus or minus about five feet, but will work pretty well for this use.

    If your sketch is right, you shouldn’t be getting water out at the house at anything above a trickle, ever.

    If your sketch is right, you need to install a 60-80 switch, which has internals designed for the higher pressure, and adjust it up slightly. Pressure Switch 9013GSG2J25 SQUARE D 60-80 PSI - HEAVY DUTY https://www.amazon.com/dp/B01LR89QH6/ref=cm_sw_r_cp_tai_enwYDbFV7YSP0

    You will also need to increase the precharge pressure for your well tank to 2-psi less than the cut in pressure of our pump to avoid bursting the internal bladder. Sorry to say it, but you may already be too late, and need a new tank.
     
    Last edited: Nov 11, 2019
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  8. Nov 11, 2019 #8

    rickwhoo

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    Could the pressure tank be his whole problem???
     
  9. Nov 11, 2019 #9

    Kenyon

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    The tank pressure was at 65 PSI when it was shutting off before. Now I have it adjusted so that it shits off at 85 PSI and kicks on at 65 PSI. I adjusted it yesterday afternoon and it has been working fine ever since. Thanks again for the help!

    I am not 100 percent sure about the 150ft in elevation. That is just an eyeball estimate.
     
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  10. Nov 11, 2019 #10

    Diehard

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    @FishScreener ...I'm curious as to where/how you came up with the 0.1 gpm.
     
  11. Nov 11, 2019 #11

    Diehard

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    Glad to hear it.
    Now, if you're curious, check you pressure in the cabin(of course it will fluctuate by approx. 20 psi since that what the pressure switch differential is set for) and you'll find out your height above the gauge at the tank. PSI x 2.31 = Feet

    EDIT: Example...PSI at tank say 85 - PSI at cabin say 50 = 35 psi x 2.31 = 80 feet
     
    Last edited: Nov 11, 2019
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  12. Nov 11, 2019 #12

    Kenyon

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    The 1-way valve (aka check valve) I took out was up at the cabin between the cabin spigot and the cabin. I installed another one down by the well just on the cabin side of the pressure tank. I think I included it on the diagram, but don't remember for sure now.

    Assuming my estimation of 150 ft is correct, that is only a total of 225 ft from the pump to the sink. That doesn't seem like much considering most wells around here are 200 feet or deeper. I looked up the specs for a typical 1 HP submersible pump and it said it was rated at 600 feet of head pressure. That wasn't my specific pump, so there could very well be some discrepancies there.

    I will order the bigger switch as you suggested. I didn't realize that it would be an issue.

    As far as the pressure tank goes, it says it is rated for 100 PSI, but I did not adjust the bladder. I will make sure I get that done, as well as installing Google Earth to get a better estimate of elevation changes. The k you for your advice.
     

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  13. Nov 11, 2019 #13

    Kenyon

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    Sadly, I don't have a pressure gauge aside from the one that is plumbed in at the tank. The pressure is sufficient for getting the dishes done and anything else we need it for (unless there is some other reason I need to check the pressure?).
     
  14. Nov 11, 2019 #14

    Diehard

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    When you adjust the air pressure in your tank, make sure there's no water pressure on it. Google it if you are not familiar with the proper procedure.

    No you don't have to check the pressure at the cabin. Just that it would reflect the elevation difference between the tank and cabin.

    If you had the actual pump performance curves for your pump you could figure it out that way also. I won't confuse you with that.
     
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  15. Nov 12, 2019 at 2:54 PM #15

    fixitron

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    The pressure tank and pressure switch should be at the cabin, not down at the well. The power should come from the house, with a 10 ga. well wire or UF cable from the pressure switch to the pump.
     
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  16. Nov 12, 2019 at 7:17 PM #16

    Kenyon

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    Yes, Google/YouTube has been pretty helpful with a lot of this. Thank you.
     
  17. Nov 12, 2019 at 7:20 PM #17

    Kenyon

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    Well, crap! I wish I would have known that before I did all of this. I guess I can still move it fairly easy.

    I did use 10 gauge wire in 1/2" conduit to power the pump. Used well specific wire from the pressure tank to the pump, then conduit from the tank to the cabin.
     
  18. Nov 12, 2019 at 7:30 PM #18

    Diehard

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    When/if you do move it up to the cabin level, be sure to readjust that pressure switch(lower) to reflect the new elevation. Otherwise you would have over 100 psi to the cabin, assuming of course the pump had that capability.

    And the air pressure in the tank.
     
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  19. Nov 13, 2019 at 7:58 AM #19

    FishScreener

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    I did a quick hydraulic horsepower calculation: calculated with the equation HHP=P*Q/1714, where P stands for pressure in pounds per square in., Q stands for flow rate in gallons per minute, and 1714 is a conversion factor necessary to yield HHP in terms of horsepower.

    So, you set the horsepower to the one horsepower of the pump, and use the set depth plus the height to the house, convert to get feet of head to psi, solving for the flow or Q is straight forward. This is assuming that his pump is 100% efficient at converting the wire horsepower to hydraulic horsepower which is impossible. So, something in the description is wrong.

    I used to be the pump test engineer for a water district, and test all the new pumps they bought at the factory prior to shipping, to assure they would meet the contract minimums. I did a lot of wire to water horsepower calculations. When you start looking at the cost to power an inefficient 500-hp pump for a ten year life, the costs get really large.
     
  20. Nov 13, 2019 at 1:32 PM #20

    Diehard

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    Thanks!
    I too got involved in pump sizing, factory test witnessing, etc.
    I use the same formula for estimating purposes.
    I think if you double check your calcs you will likely find a typo somewhere.

    Assume motor = 70 % eff
    GPM = 1714 x 1 HP x .70 / 97 psi = 12.4 GPM
     
    Last edited: Nov 13, 2019 at 1:58 PM

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