PVB pulsates on and off

Discussion in 'Irrigation' started by sencinia, Oct 27, 2007.

  1. sencinia

    sencinia LawnSite Member
    Posts: 5

    Just replaced 2 above ground 3/4" valves with 1" below ground.
    Could the size be the cause? Only happens when it comes on.
    Sometimes it comes on after a fews pulses. Sometimes the PVB just stays open.
    Need help. First time this has happened.
     
  2. irrig8r

    irrig8r LawnSite Platinum Member
    Posts: 4,533

    I've only had this happen when there isn't enough flow to keep the float open... i.e. a drip irrigation zone. Sometimes it's required running two small drip zones at once.
     
  3. sencinia

    sencinia LawnSite Member
    Posts: 5

    Believe I solved it.
    I adjusted the outlet valve on PVB to 3/4 on.
    Valves open up just fine. All zones work fine also, i.e all sprayers pop up
    just as before.
    Can anyone explain why this works?
     
  4. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,298

    Why isn't it wide open?
     
  5. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,799

    Sometimes the flow control needs to be tuned to zone at hand. I've seen it more than a few times.
     
  6. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,298

    Why would you use the PVB for flow control? Why not use the valve, assuming it has flow control?
     
  7. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,799

    I was referring to the flow control on the valve.
     
  8. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,298

    Ah, yes, that was what you meant by zone. [​IMG]

    Oh btw DW, one of the developers I have done some work with got his server hacked. Got all the code if your interested in a peek.
     
  9. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,799

    Amusing.

    If the code base I work on were to get leaked to the public, we would have a serious public relations problem on our hands.

    Let me guess, typical LAMP setup server?

    They are not as bulletproof as people think.

    Laugh if you want, but we run a farm of Win 2k3 servers with IIS 6.0.
     
  10. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,449

    Closing down the outlet valve on a PVB assembly will prevent excess pressure drop in the PVB when a zone valve opens, although you probably would be better off using flow-controls on the valves for this.
     

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