RPZ Backflow installations question

Discussion in 'Irrigation / Sprinkler Forum' started by ctlogistics, Sep 2, 2013.

  1. ctlogistics

    ctlogistics New Member

    Messages:
    4
    Location:
    IA
    I need to install a Wilkins 975XL RPZ backflow preventer for my in-ground irrigation system. I'm getting conflicting answers from multiple city inspectors and the around the web.

    First question: Does a RPZ backflow preventer have to be installed above the tallest sprinkler head? One city inspector says yes, one says no.

    Second question: The instructions for installation say the maximum height off the ground is 30". The best place for this to come out of my house would be about 40"-50" above grade (backside of walk-out). City inspectors aren't sure about this maximum. I've seen new home installs (less than 6 months) where the units are installed more than 30" above grade.

    Any clarification would be great.
    Thanks.
  2. johnjh2o1

    johnjh2o1 Plumbing Contractor for 49 years

    Messages:
    1,142
    Location:
    South*East
    Most codes call for a PVB backflow device on an irrigation system. That device needs to be installed 12" above the highest head on the system. An RPZ device doesn't. RPZ's are more expensive the PVB's. I would check with your inspectors to see if you can use a PVB.

    John
  3. ctlogistics

    ctlogistics New Member

    Messages:
    4
    Location:
    IA
    I wish the PVB would be enough. $75 vs. $250 - would be nice. However, the city was very specific about the reduced pressure device.

    The fact it doesn't have to be higher than 12" above the sprinkler head is a blessing. I appreciate the clarification.

    Now if I can just figure out the reasoning behind the 30" maximum clearance.

    Thanks for you reply. Very much appreciated.
    Last edited: Sep 3, 2013
  4. Wet_Boots

    Wet_Boots Sprinkler Guy

    Messages:
    798
    Location:
    Metro NYC
    There is no technical reason for a maximum height for the RPZ mounting. Considering the cost of pipe, though, economy argues well enough.
  5. johnjh2o1

    johnjh2o1 Plumbing Contractor for 49 years

    Messages:
    1,142
    Location:
    South*East
    In my area RPZ must be installed 12" above the ground. The only reason for this is so you can see if the relief is dumping.

    John
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