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Backflow preventor suggestions

Discussion in 'Irrigation' started by silvercvic, Oct 25, 2006.

  1. silvercvic

    silvercvic LawnSite Member
    Messages: 41

    I am totally new to all this and I am trying to learn as much of this as possible before I spent $$ on trial and error.

    I have read irrigationtutorials.com over and over and picked up a book on sprinkler systems.

    I have completed dimensions and approximation of where I want to water and after checking with local code, my next step is to select a backflow preventor. I have noticed most installs on this forum uses a vacuum breaker (PVB), but since my highest sprinkler head sits in a retaining wall (sits pretty high off the ground), I have chosen to use either a Reduced Pressure Backflow Preventer or a double check backflow preventor since elevation of the BP would not be an issue.

    Now which would be preferred and cost-effective (R.P. unit -or- Double check)? My county requires that it be ASSI code 1013 or 1020.
    I have researched these brands: Febco 860/860U and Wilkins 975XL
    Does anyone have any other suggestions? Brands/model
    I was also wondering why Febco is cheaper to Wilkins by over $60

    Does anyone suggestion going with a Double-Check Backflow preventer, if so why?
  2. Dirty Water

    Dirty Water LawnSite Fanatic
    Messages: 6,794

    Doublechecks can be installed in a valvebox below grade. They don't have relief valves to stick open and are cheaper.

    If your county allows them, go for it.
  3. Kuma

    Kuma LawnSite Member
    Messages: 1

    The Double Check backflow preventer is not rated for irrigation applications according to the USC Cross-Connection Manual. A Reduced Pressure Zone backflow preventer or Pressure Vacuum Breaker are rated for irrigation applications.
  4. Dirty Water

    Dirty Water LawnSite Fanatic
    Messages: 6,794

    Not every county goes by the USC manual, my area for example, requires doublechecks and will fail you if you install a PVB.

    As far as safety goes, A doublecheck should be inspected yearly for proper function, but I don't think a RPZ's toxic backflow rating is really needed in lawn sprinkler applications. Morgues, carwashes and factories yes, but lawn sprinklers? I'd fathom even a simple dual check would be fine.
  5. silvercvic

    silvercvic LawnSite Member
    Messages: 41

    Do you recommend any brands/model? I would love to see an installed unit (valve box) if someone got one.

    Also, the local plumbing store around me only carries a WATTS 009ms, anyone recommend this unit?
  6. Dirty Water

    Dirty Water LawnSite Fanatic
    Messages: 6,794

    We exclusively install Febco 850's. I've found that the handles test to rust off on the Watts.
  7. silvercvic

    silvercvic LawnSite Member
    Messages: 41

    Excuse my inexperience, but what do the 4 nozzles on top of the 850s do?
  8. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,517

    Virginia is probably working to standards used by the BOCA codes, and cannot use double checks. {which would explain the OP not mentioning ASSE standard 1015} Best would be a PVB (pressure vacuum breaker) if you can install it at the needed height, otherwise the RPZ would be used. Eliminate the Febco 850 from your shopping.
  9. jerryrwm

    jerryrwm LawnSite Bronze Member
    Messages: 1,274

    Jon, The reason they classify lawn irrigation systems as toxic is because of the chemicals that we put on the lawns, along with pet deposits, etc. It is pretty nasty stuff and it getting back in the potable supply is not something I want to deal with. The chances of this happening are pretty slim at best, but it only takes one time with some of those highly toxic chemicals and 'poof' someone dies or gets sick.

    Double checks are only as good as their last test. They can fail and not be evident until the next time. A little thing like a piece of string can foul both checks. nd since they are many times buried in the valve box, there is a potential for cross connection if the box is flooded. In fact some areas have gone so far as to require a fitting/nipple/cap on each of the testcocks. And this nipple has to be above grade. These municipalities have the codes so that the valve box is not flush with the grade but at least 2" above grade so they can't be submerged. Real pain in the arse if there isn't a landscape bed to hide the box in.

    And a dual check has no socially redeeming value other than being installed on a domestic supply line to the house. It might help keep the crap from the house from getting sucked into the city main.

    RPZs and PVBs are still the only mechanical types of backflow prevention rated for toxic use.
  10. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,517

    AVBs also carry a rating for toxic use, but they are not so widespread in usage. Their history of misuse, as taking the place of a PVB, has given them a poor reputation.

    Since the regional plumbing codes I read are all requiring toxic-rated devices, there would be a point in looking to use them, where possible. DCVA users will no doubt be kicking and screaming if and when the rules change in their territory.

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