Built in Backflow preventors

Discussion in 'Irrigation' started by sheshovel, Aug 4, 2005.

  1. sheshovel

    sheshovel LawnSite Fanatic
    Posts: 5,112

    Hey,is the device on a freezeless sillcock a backflow device?I know it keeps water from backflowing into the bib so it won't freeze,but does this give any backflow protection like an
    added device would?They are called backflow preventors also are they really?
    Say I am installing a batt opp timer,filter,W press Reg, and drip system coming off one of theses bibs,do I also need to add a back flow device on these types of bibs?I have been but do I need to?
     
  2. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,992

    A sillcock with a vacuum breaker is not adequate for any sprinkler protection, since the sprinkler valve(s) you add negate any upstream atmospheric vacuum breaker function. Make your battery operated valve an anti-syphon type, if elevation works in your favor. Otherwise, in California, it would be time for an RPZ.
     
  3. sheshovel

    sheshovel LawnSite Fanatic
    Posts: 5,112

    I'm talking a drip system here.
     
  4. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,992

    And what makes you think drip is any different from regular sprinklers, when it comes to backflow prevention? A cross-connection is a cross-connection.
     
  5. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    That device is called an "atmospheric vacumn breaker" or AVB. An AVB is not rated and becomes ineffective if any type of valve is installed downstream of the AVB. Anti-siphon valves are the same type, and some of those california manifolds you see incorporate a mastervalve. When they do this, they eliminate the compliance to code that the anti-siphon valve provided. For your described situation, either a PVB or RPZ should be installed and can be fed by the hose bib, but you cannot consider the AVB of the hose bib to be an effective backflow if you put a valve in past it.
     
  6. sheshovel

    sheshovel LawnSite Fanatic
    Posts: 5,112

    Ok this is how I have been hooking them up--
    freezeless sillcock-
    PVB valve,filter,
    water pressure reg 25psi-
    batt/op timer usually Orbit 6015-
    line adaptor and then out with my dripline.Is this correct as long as it is 1'above my highest emmitor?
    Also I have a problem with the PVB valve and WPRREG dripping water onto the timer and gettting the batteries wet when they relieve pressure and stop bck flow when the unit shuts off .I have no way I know to install a regular valve from these set ups because they only stick out of the wall a tiny ways.In fact they are so close to the wall,I can barely get teff tape around the threads of the bib.
     
  7. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,799

    Why are you putting teflon on hose thread? Hose fittings do not seal on the thread, they seal on the O-ring in the female fitting.

    I'm with Wet Boots on this one. You need to start installing RPZ's (since DC's aren't allowed in Cali???)

    Personally (since I'm still allowed to use a DC), if I have to come off a sillcock, I'll use a 3/4" brass 45 with a hose to pipe thread adapter attached to Lee Valleys excellent brass Ball valve Y. Thread that onto the sillcock and align it so it points down towards the ground. Then I use a sch 80 nipple to drop below the ground and elbow into my doublecheck.

    Then it goes off to the valve, pressure reducer and fitler and back up to the drip line.

    This is much cleaner, the customer still has a hose hookup, and theres no junk hanging off the house.

    Lee Valley Valve (Not my picture):

    [​IMG]
     
  8. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,992

    I think the 'backflow protection' part of those frostproof sillcocks is more like a vacuum relief valve (Ever see a sprinkler system with nothing but a brass vacuum relief valve for backflow protection?)

    I mentioned the RPZ for cases where you might be running the drip uphill from the house. They do make 1/2 inch RPZs that cost less that the usual. If you were on flat territory, and all you were doing was one zone of drip, you might feed it through an antisyphon valve that has the solenoid replaced with a battery-operated one, such as Rainbird sells. I see they even list an assembled combination of 3/4" inch antisyphon valve, 200 mesh strainer, and 30 psi regulator.
     
  9. sheshovel

    sheshovel LawnSite Fanatic
    Posts: 5,112

    OK thanks guys!I appreciate the replys.So what I am doing is not good?Great Idea Holland ecept alot of these are over cement driveways,no way to get underground.I will take some pics today to show you what I mean.
     
  10. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,992

    Unburied, I suppose nothing is going to really look good. I would always try to have everything but the sillcock connection as regular pipe, either threaded or slip. I'm sure any brand-name battery-powered solenoid operator will cost more than an Orbit battery-powered valve, which is why I thought trading a PVB for an antisyphon valve would make economic sense. Another way to get proper backflow in your setup, assuming flat ground, is to have an atmospheric vacuum breaker right after the Orbit valve, which would meet the requirement of not being under pressure 24/7. Richdel used to offer just the AVB portion of their antisyphon valve, and Hunter lists an AVB in their catalog. And there are the classic brass AVBs, which could be had in a more-economical 1/2 inch pipe size.
     

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