Visual Difference in old PVB versus AVB?

Discussion in 'Irrigation' started by WalkGood, Jun 4, 2007.

  1. WalkGood

    WalkGood LawnSite Bronze Member
    Posts: 1,910

    Rainy day question.......


    The other day I saw what I think is an old atmospheric vacuum breaker located outside the house on the copper feed to a residential manifold. But I am not sure if it is a pressure vacuum breaker.

    It has no valve handles. Nor any ports of any kind, except the 3/4" input on the bottom and the 3/4" output on the side. The canopy was missing and you can see the plastic poppet inside. There is a single cast-in-place bar across the top where the canopy would go. A single post in the center of the white plastic poppet floated into the bar. Well, it didn't "float" and seat correctly when I turned on the water feed to it. I poked at the poppet until it seated, however it does seep some water.

    So, this is an AVB? Or a PVB? Did PVB's ever come without built-in valves or other ports (that I see on new ones) besides the inlet/outlet?

    What visual differences are there in AVB versus PVB?
     
  2. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,006

    It's an AVB, and non-functional by definition. Get it changed to a PVB, if the elevation requirements (at least a foot higher than any downstream pipe or head) can be met.
     
  3. WalkGood

    WalkGood LawnSite Bronze Member
    Posts: 1,910

    I told the customer that it should be replaced w/PVB or removed (we do not require any residential vacuum breakers or dbl checks here anymore). But this , um, er... "thrifty" customer didn't want to. Typical "it has worked for years and years, no need to change it" response.
     
  4. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,006

    You basically want to put some distance between yourself and sprinkler systems without functional backflow protection. No one wants to let go of a paying customer, but the AVBs pretending to be PVBs are on my 'stay away' list.
     
  5. PurpHaze

    PurpHaze LawnSite Fanatic
    Posts: 5,496

    We have old ones where plumbers put them in the boxes next to the right angle valves (all brass, of course).:dizzy:

    That site (which is 1/2 county DOE) had the county pay to put in an automatic system last year but we had final approval on what was done. A PVB went in protecting the entire site.
     
  6. PurpHaze

    PurpHaze LawnSite Fanatic
    Posts: 5,496

    I had a hard time understanding this whole thing but are you saying that your area doesn't require any type of backflow prevention or just certain types on residential installs?
     
  7. Walkgood get a camera and post pics. I want to see this thing.
     
  8. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,006

    About the only finctional AVBs I ever see are ones I installed, often on some systems that had no backflow protection, and above-ground manifolds (valve outlet pointing down) - Richdel used to sell just the AVB portion of their antisyphon valves, which made them good for retrofitting those manifolds.
     
  9. PurpHaze

    PurpHaze LawnSite Fanatic
    Posts: 5,496

    Cut a brass or plastic ASV in half and you have it. :)
     
  10. PurpHaze

    PurpHaze LawnSite Fanatic
    Posts: 5,496

    And then...

    febco710-2.jpg
     

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