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dual water supply

Discussion in 'Irrigation' started by Dirt Boy, Feb 22, 2013.

  1. Dirt Boy

    Dirt Boy LawnSite Senior Member
    Posts: 487

    customer wants to be able to utilize both well & city water for sprinkler system.
    Attached a simplified diagram.
    What should I be considering here.
    1. House would have a PVB
    2. A check valve between well and city (to keep city out of well)
    3. Pump start relay with no flow/overheat protection.

    What else am I missing?

  2. HanktheCowdog

    HanktheCowdog LawnSite Member
    Posts: 13

    A PVB is not allowed to be used with back pressure. You need an RPZ. In Texas, if you even have a well and city water on the same property (not even connected), they will make you put an RPZ on the downstream side of the city water meter. They don't want any well water getting back into the city side. Some of the wells in town are highly contaminated.
  3. DanaMac

    DanaMac LawnSite Fanatic
    Posts: 13,156

    If I recall from our local codes, there must a way to disconnect the mainline pipes between the backflow valve, and the well. They don't want any way for water from the well to put back pressure on the device even if it were an RP, as any device can fail. So there must be some kind of disconnect, possibly with unions and ball valves, at least for our codes.
  4. Mike Leary

    Mike Leary LawnSite Fanatic
    Posts: 21,974

    What those dudes said. Up north, wells are considered a "cross-connection" to City water and only permitted with a RPZ installed AT THE METER and tested annually. This is called "Premises Isolation" and I've heard some horror stories about hot water heaters in a "closed loop" system. Best practice would be two separate systems, avoiding "cross connection" connected to the same clock. Even so, the purveyor has the right to call for a RPZ. :cry:
  5. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,648

    Aside from local purveyor preferences, the uppermost requirement will be in the construction codes. That will be for an RPZ to isolate the house from the sprinkler system, which will be considered a toxic backpressure situation.

    Even if someone is in a locale without that requirement in their local or state codes, they would be extremely foolish to not use the RPZ.
  6. Dirt Boy

    Dirt Boy LawnSite Senior Member
    Posts: 487

    Thanks guy's, makes sense, and that's the way I will bid the job. That is what our reg's are as well, RPZ, no other requirements other than that. should have known, or figured that out first.
  7. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,648

    Protection for the well itself might be included, or at least planned for, in terms of pressure loss when added on, sometime in the future.
  8. Mike Leary

    Mike Leary LawnSite Fanatic
    Posts: 21,974

    When I was a CCS, no matter what the contractor or the the client told us, the possibility of some dimwad down the road making a repair and tying into the potable was probable, so we mandated RPZs. Our lawyers mandated it to protect the City liability.
  9. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,648

    RPZs have been Washington State code for awhile now, in a irrigation backpressure situation, so no surprises there.
  10. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,308

    No "might" about it ........

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