Blow air through PVB?

Discussion in 'Irrigation' started by johnboy37, Jul 30, 2011.

  1. Mjtrole

    Mjtrole LawnSite Member
    Posts: 226

    Same as here, its a waste of time explaining this to anybody we always would get "that's the way its been for 10 years" so we just dropped the matter a together.

    It's rather comical, we have some cities that will not pass a backflow unless there is a 3/4" threaded drain cap that is used to drain/winterize from and others that will not pass a backflow if there is any threaded connection before the backflow.
     
  2. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,449

    I can see worries over an "opportunity to contaminate" that a garden hose connection upstream of a backflow preventer presents, but I would worry far more over losing the low-point drainage that those blowout valves provide, for a system supply that exits the house foundation above grade.
     
  3. AI Inc

    AI Inc LawnSite Fanatic
    Posts: 25,153

    We plumb them all before the pvb. If thye system is being inspected , we will install a plug there and then put in a boiler drain come blowout.
     
  4. DanaMac

    DanaMac LawnSite Fanatic
    Posts: 13,156

    if done properly, and if you set your compressor PSI at a manageable level, there should be no problems. If the hot air is going to warp or damage a bonnet/poppet/check valve, then it would also warp or damage a zone valve, pipe, or heads. It's all in how you do it, no different than an install.

    Now if it's a massive system, with dozens or hundreds of zones, and the compressor is going to be pushing for an hour, then sure they may be more heat than you would like. On a system like that, if there is no blow out port, I will find a manifold or mainline drain to hook to.
     
  5. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,449

    I wonder, who here has seen a melted backflow from compressor heat?
     
  6. DanaMac

    DanaMac LawnSite Fanatic
    Posts: 13,156

    I've seen damaged internal components, but whose to say that they were not already like that before I blew out the system. I've seen some weird things with PVBs/RPs where components are damaged but the unit does not leak at all.
     
  7. Mike Leary

    Mike Leary LawnSite Fanatic
    Posts: 21,603

    I've seen warped plastic check retainers and ball valves. It can happen. :cry:
     
  8. AI Inc

    AI Inc LawnSite Fanatic
    Posts: 25,153

    And Ive seen strippers strip for me for free. It can happen, but its not the norm.
     

Share This Page