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Blow air through PVB?

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

  1. johnboy37

    johnboy37 LawnSite Member
    from Mass
    Posts: 3

    I just had a plumber put in a backflow for me, they put in a Watts 800. They put the connection for winterization upstream of the PVB, and said that we can just blow out the system through the PVB to winterize. They said "they just did a 1.4 million dollar home and they always do it this way".

    I was under the impression that I should have a blowout tap after the downstream valve of the pvb, then I could hook up the air there and blow the system out with the downstream valve closed, so the air doesn't blow through the PVB.

    Who was right?
  2. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,673

    With your own home compressor, no worries - with a hot jackhamer compressor blowing 250-degree air, worries
  3. mitchgo

    mitchgo LawnSite Silver Member
    Posts: 2,780

    Having a blow out installed prior to the back flow assembly is illegal and is a form of cross contamination.

    Up here when we see this.. We always recommend to take it out and install it down stream of the bfp
  4. bx24

    bx24 LawnSite Senior Member
    from MA/TX
    Posts: 503

    Depends on your state. In MA/CT we blow out AT the PVB for winters (if no unions to remove). Some install a boiler drain before and use that or use the test ports....
  5. Mike Leary

    Mike Leary LawnSite Fanatic
    Posts: 21,976

    I never blew through any assembly, used a 7 psi bicycle pump instead. I suppose a unit could be blown if the operator had a compressor that could be dialed-down, but that seems like a waste of time, plus the possibility of melting the the checks. I installed a quick-couple just south of the backflow with brass fittings to absorb the heat of the compressor and blew my heart out with this method for thirty years.
  6. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,673

    Try not to devalue your contributions by assuming your local customs are the law of the land. Besides, the upstream blowout valve is only an opportunity for someone to introduce contamination, and that is a different animal than an actual cross-connection.
  7. mitchgo

    mitchgo LawnSite Silver Member
    Posts: 2,780

    Hence why I said Form of cross contamination

    Hey I follow the codes of good ol California. Besides.. Back flow preventors do not like air which causes the checks to slam about and heat up/ break/melt

    Just the other day I went out to a new customer for a stuck valve. When I took apart the valve. I found a part of a broken spring from the back flow assembly
  8. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,673

    It is not a form of cross-connection period, any more than upstream testcocks on a backflow preventer are a form of cross-connection.

    (there is no such thing as "cross-contamination")
  9. mitchgo

    mitchgo LawnSite Silver Member
    Posts: 2,780

    Well I be-sure to be like this guy and then tell you it's not a cross contamination.. k?
  10. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,673

    There is "cross-connection" and there is "contamination" - there is no "cross-contamination"

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