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Strange pressure behavior

Macster
Macster Member Posts: 6
edited September 2015 in Plumbing
Hi..
I have an 18 year old submersible pump 30/50. My pressure switch is also set at 30/50 and my water tank is set to 28 psi. I noticed that when pressure is building up, it goes passed 50 psi to about 54-55 psi then comes down slowly to 48-49 psi and stops. I have even checked after a couple of hours and it won't go down after it stops.

At first I thought I had a leak somewhere, but then after I saw the pressure would not continue to drop even after hours of not turning ON a faucet I ruled out that possibility. So, I replaced the pressure switch with a new one, but the same thing happens. It doesn't matter the adjustment I make..for example, if I set the psi to 20/40, once the pressure gets to 40, it will come down to about 34-35 psi..it will always drop about 4-5 psi from the max, but won't move any further. Is this normal?

Comments

  • Zman
    Zman Member Posts: 7,434
    What you are seeing does not sound alarming. It may just be a characteristic of the gauge. You could try getting a second opinion by putting another gauge on a hose bib.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Macster
    Macster Member Posts: 6
    edited September 2015
    I've tried that as well.. I should have mentioned it... it shows the same thing. - I have also tried different newer gauges..they all drop as well.
  • Zman
    Zman Member Posts: 7,434
    How long does it take for the pressure to settle after the pump turns off?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Macster
    Macster Member Posts: 6
    just a couple of minutes..if that.
  • Macster
    Macster Member Posts: 6
    I think this started happening after I replaced my water tank, but Im not sure... I do remember that it was not doing that when I first moved in. - I always check the water tank's pressure every 4 months and it only loses a couple psi, so I had ruled out the tank being an issue.
  • JUGHNE
    JUGHNE Member Posts: 10,315
    Is your new switch a 30/50 or a 20/40? I don't think you can adjust a 30/50 down to 20/40 very well. When you check tank pressure is all the water drained from the system? Tank should feel empty and easy to rock back and forth.
  • Macster
    Macster Member Posts: 6
    my switch is 30/50, I was just saying an example as it doesn't matter which psi is set, it will always drop down 5-6 psi. - Yes, I drain the water from the system.
  • JUGHNE
    JUGHNE Member Posts: 10,315
    Are the pressure switch, gauge and air tank located close to each other or is the switch or tank remote from the others?
  • Macster
    Macster Member Posts: 6
    edited September 2015
    They're right next to each other.
  • JUGHNE
    JUGHNE Member Posts: 10,315
    Don't know what to say. One thing for sure was that coming back a year or two later to a system I did work on previously, the pressure gauge was always non functional from water hammer.
    (Also no one wanted to pay any more than $6.00 for a gauge :| )

    Only other guess is your new tank bladder operates differently than the old. Maybe more flexible, over flexes and then rebounds. Or cold well water cooling the air in the bladder enough to drop the air pressure charge...long shot??

    Just so the system doesn't short cycle and wear out components.
    Zman
  • Zman
    Zman Member Posts: 7,434
    JUGHNE said:

    Don't know what to say. One thing for sure was that coming back a year or two later to a system I did work on previously, the pressure gauge was always non functional from water hammer.
    (Also no one wanted to pay any more than $6.00 for a gauge :| )

    Only other guess is your new tank bladder operates differently than the old. Maybe more flexible, over flexes and then rebounds. Or cold well water cooling the air in the bladder enough to drop the air pressure charge...long shot??

    Just so the system doesn't short cycle and wear out components.

    This is a good guess in my mind. Keep in mind it is not broken or even malfunctioning. It just is not as it was before. Interesting puzzle though.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Steamhead
    Steamhead Member Posts: 15,765
    Where is the pressure switch connected to the system piping?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • JUGHNE
    JUGHNE Member Posts: 10,315
    edited September 2015
    He mentioned that all the components were together.

    The cheap $6.00 gauge I mentioned had its advantage that it failed early and was never looked at by owner anyway until something malfunctioned. ;)

  • RobG
    RobG Member Posts: 1,850
    The only thing I would add is to make sure that the pipes are clear of any debris. I have seen many pressure switches and gauges malfunctioning due to blockages or partial blockages.
  • JUGHNE
    JUGHNE Member Posts: 10,315
    Yes Rob your'e right, just like a pressurtrol on steam.
    (Have had to drill out ice on one water pump control 1/4" line :o )
  • MikeG
    MikeG Member Posts: 169
    Most submersible pumps have a built in check valve. On an 18 yr old pump, it may be bleeding past until it seats. Also depending on depth of well and pump and distance to house they often recommend additional check valves every so many feet. You can get some weird things happening if you have a long distance. Just another possibility. I have an additional check valve near my pressure tank. As stated maybe the new tank has more give in the bladder or diaphram.