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Dumb questions (maybe) but I'd like to know

Discussion in 'Irrigation' started by Waterit, Jul 30, 2008.

  1. Waterit

    Waterit LawnSite Silver Member
    Messages: 2,931

    The setup:

    (2) 7-1/2HP submersibles, each producing about 120GPM @ 70PSI +/-, and tied into same 2-1/2" mainline. Each well has 2" pressure relief valve BEFORE 2" PVB.

    33 zones spread across (2) ICC's, each ICC has its own Hunter PSR-B and each controls one well.

    The questions:
    1) There is no protection from one well pumping against the other except for the PVB's, which I don't think are built to withstand that much flow at that much pressure. I want to install a check valve AFTER each PVB to prevent the back-pressuring between pumps. Good idea/bad idea? If good, what size check? Match mainline size, or go bigger?
    2. When either pump first turns on, there is a horrendous hammer effect on the piping, specifically the MA coming out of the PVB and the 1st 90 that turns the pipe vertical. It was suggested to install a pressure tank to absorb some of this hammer. Smart/stupid? If smart, what size tank?

    ::::moves away from keyboard, looks for fireproof suit::::
  2. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,527

    Too bad you can't have the supply under continuous pressure, with tanks and pressure switches (and maybe even CSVs)
  3. greenmonster304

    greenmonster304 LawnSite Gold Member
    Messages: 3,666

    it seems to me if you had a check valve on each well and they are plumbed into the same main if there was ever a pressure difference between the two wells the one with weaker pressure would not be able to open. But i might be missing some factor.
  4. Waterit

    Waterit LawnSite Silver Member
    Messages: 2,931

    Could have it that way, but personally I like a straight pump-start with a well. And with the volume of water (and lack of irrigation knowledge amongst the maintenance staff) I'll probably be leaving it a straight pump-start.
  5. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,527

    But you do cure the startup hammer with a 24/7 pressurized setup.
  6. Mike Leary

    Mike Leary LawnSite Fanatic
    Messages: 23,153

  7. bcg

    bcg LawnSite Bronze Member
    from Tx
    Messages: 1,865

    Or, you could just replace the PVB's with RP's. PVB's aren't rated for back-pressure at all so if you're worried about that, then you definitely do need to do something.
  8. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Messages: 2,781

    I'm reading ONE main line. Why is the PVB after EACH pump? One PVB with check valves to protect the pumps from each other would be a better setup, but I'm not there looking at it. A single pump start being shared by two controllers is another nightmare, especially if the controllers are a significant distance apart. If your worried about down stream leaks, switching to a MV and putting the pumps on pressure switches would be easier and safer. Stacking the pressure switches for demand would again be safer for all aspects. If hours on the pump is an issue, then you can trade the sequence of primary and secondary either by installing plugs that could be switched, or by trading the switches annually. The worst part of these type of questions is NOT being there. I would bet that some obvious solutions would be there for many of us if we were on site.

    Any chance of some pictures?
  9. Mike Leary

    Mike Leary LawnSite Fanatic
    Messages: 23,153

  10. Waterit

    Waterit LawnSite Silver Member
    Messages: 2,931

    Two pumps, two controllers, two pump-starts, one mainline, although each pump has its own feed into mainline. Don't know where mainline is tied together (we didn't do original install, just controls package).

    PVB's are mounted on top of each pump - remember they are submersible pumps.

    I may put in MV's, that would solve with back-pressure problem, but REALLY hate the idea of going to pressure switches, especially on 440VAC 3-phase pumps.

    Will take pics tomorrow and post.

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