Anti-siphon valve vs. Inline valve

Discussion in 'Irrigation' started by Pecker, Sep 19, 2005.

  1. Pecker

    Pecker LawnSite Bronze Member
    Messages: 1,454

    Hi what's up! Searching didn't help much because alot of the lingo went over my head because I'm not a pro. I'm building a sprinkler system for my house. Plans have been drawn up by Rainbird. I have a few simple questions before I start:

    1. I'd like to use inline valves because it would look much nicer to conceal the valves in a box in the ground. But the valves that go above ground (the anti-siphon valves) have the anti-siphon feature. I gather that the anti-siphon device prevents contamination into my house line via backflow. Is that correct?

    2. Could I just use inline valves and use a backflow preventer instead of anti-siphon valves? What does a backflow preventer look like? Home Depot didn't have any on the shelf - where would I buy one? Where would I mount it in the system?

    3. Using inline valves, how to you connect them so that you can take replace a valve if it breaks. . .is there a way to set it up so you can unscrew the pipe from the valve or something so its not so permanent?

    4. Lastly, I live in northwest Louisiana and it doesn't snow or ice up here but about every couple years at best, but it does get in the upper 20's oftentimes. Do I need to install drain valves or even worry about the pipes breaking since they will be below the soil?

    I know this is lots of questions. To make it easier, just type the number your responding to if it will help. Thanks a million in advance!
  2. Planter

    Planter LawnSite Member
    from Utah
    Messages: 214

    1. Yes, That is correct.

    2. You can place a PVB on the system between the point of connection and the first break in the line, i.e., hose bibb, valve, quick connect, etc. You would be best getting the PVB or reduced pressure double check at a sprinkler or plumbing house.

    3. The easiest way is to use an Action type manifold and a union on the other side. I use the Action manifolds, but don't use a union on the downstream side, I just leave enough room to cut it out and install a Dawn quick fix.

    4. I've had mixed success with drains in the lines and have found that they usually fail, so I install a quick connect and blow out the system each year.

    Good luck!
  3. drmiller100

    drmiller100 LawnSite Senior Member
    Messages: 562

    call your local plumbing inspector. he will tell you what he wants for antisiphon.
    call your local sprinkler installer and ask him if you need to blow out sprinklers each year.
  4. Pecker

    Pecker LawnSite Bronze Member
    Messages: 1,454

    Good stuff. Thanks guys.

    Planter, a few more questions if I may:

    - what's a PVB?
    - what's a hose bibb?
    - what's a valve disconnect; is that an accessory that fits on a valve?
    - what's an Action?
    - what's a Dawn?

    Sorry for the dumb questions. . .but I really appreciate your insight!
  5. Dirty Water

    Dirty Water LawnSite Fanatic
    Messages: 6,794

    ******, I'm not a middle schooler but your name still makes me smile.

    You won't have any luck buying a back flow preventer from Home Depot, your best bet is to get one from a plumbing supply house, or order it online from someone like MTI.

    Depending on your local codes, you have a few options for a backflow preventer. The most common one in my area is the doublecheck.


    This valve keeps the water from contaminating your house water. The nice thing about double checks is that they can be buried beneath the ground in a valvebox. Which in my opinion looks real nice.

    My usual setup is to tap off my source line, and then put a ball valve in the line, and after that the double check.

    Many area's do not allow doublechecks however, and instead require a PVB (Pressure Vaccume Breaker).


    PVB's do the same thing that a doublecheck can do, but you have to mount them above ground, above the highest head in the system.

    Your other option is to use AVB (Anti-Syphon Valves) instead of using a PVB or doublecheck, but like you mentioned in your post, they are ugly :)

    I use Rainbird DVF-100 threaded valves, a lot of guys here like them. The other popular one seems to be the Irritrol 2400, I don't personally use them, but they are good valves.

    What you will find in Home Depot will be imitation valves that look similiar but will be poorer quality yet priced similar to what you would pay for a professional valve. I'd recommend ordering yours from a online sprinkler supplier (Perhaps the same one you get your backflow preventer from.)

    You can get valves that glue in, or you can get valves that have female threads. I prefer threaded valves. I thread a PVC fitting called a Male Adapter into each end (using teflon tape of course) and then glue it in, this allows me to easily replace it if I have to (Though DVF-100's pretty much never fail).


    As far as drains and winterization. Up here, irrigation systems get blown out with compressed air to evacuate the water. It sounds to me that all you'll have to do is in LA is wrap your PVB (If you use one), with a blanket if you suspect a cold snap.

    MTI is a excellent online sprinkler supply store. I'd buy stuff there over Home Depot.

    Also check out Jesse Strykers Irrigation Tutorial web page. While I don't agree with everything he says, its a great starting point for someone to learn.

    Good luck :)

  6. Planter

    Planter LawnSite Member
    from Utah
    Messages: 214

  7. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Messages: 2,781

    You've had excellent replies to all but #4. The answer partly depends on how you install your system. I worked in the DFW area for about 2 years. A freak snow or ice storm will happen, but an actual ground freeze/hard frost is a very rare thing. If you manage a minimum of 6" depth to your system, the only worry you might have for freezing would be the backflow if an above ground backflow is required. I strongly recomend you call your local plumbing inspector and find out what is prefered for your water district. I also will strongly recomend that as a homeowner, you ask and apply for any necessary permits. If do to rocks, landscape features, terraces, etc. you end up with any shallow piping, then I would recomend a manual drain for that exposed piping. Then if you do get a freeze warning, it is a simple matter of opening the drains and waiting for the weather to change. In your climate, winterizing like we do north of you is not necessary.
  8. Pecker

    Pecker LawnSite Bronze Member
    Messages: 1,454

    Excellent replies (and photos) from everyone. Lots of info and insight. Thanks a million - this has been VERY helpful!
  9. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,746

    Antisyphon valves are the least expensive way to go, and if you don't have too many valves, is not a real visual problem. (You can say something's ugly and you don't want to see it, but is a hundred dollars ugly? Three hundred? Five hundred?) - In California, where most of the sprinkler equipment companies are located, above ground sprinkler plumbing is commonplace, and no one looks twice at any of it. - Also in favor of the humble antisyphon valve is its serviceability.
  10. sheshovel

    sheshovel LawnSite Fanatic
    Messages: 5,112

    True Wet Boots and we usually build or install irrigation boxes or wooden boxes painted the same color as the house over the manifolds.Hinge the top for easy access and insulate them in some areas too.

Share This Page