Designing off 3/4" house line.

Discussion in 'Irrigation / Sprinkler Forum' started by ye, May 31, 2008.

  1. ye

    ye New Member

    Messages:
    7
    Off my house 3/4" line I installed 6 valve manifold - all 3/4". Now - 4 valves will water large zones taking 3/4" feed sprinklers. Should I:
    1) step up to 1" and run main and lateral 1", and step down just before the sprinklers? 2) step up to 1" to main, and step down to 3/4" between main and lateral? 3) run 3/4" main and lateral all the way to sprinklers?

    Thanks.
  2. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,347
    Location:
    Yakima WA
    The first thing you should do is install a backflow prevention device. The only thing you would gain be going to the larger line is a little less friction loss over a long run. 3/4" is very marginal for supplying a water system. But you must protect against cross contamination of your water supply...both yours and the city's. I would advise you to get a professional sprinkler company to go over you plans and recommend the best course of action. You could waste a lot of time, work, and money to put in a system that doesn't work the way it should and risk the health of your family and neighbors.
  3. ye

    ye New Member

    Messages:
    7
    Thanks!

    Thanks for the answer. I did my due diligence and read bunch of manuals and some threads on this same forum - so, yes - backflow preventer is already in. I was asking if I can do a step-up etc., and from your answer sounds like I can. Thanks again.
  4. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,347
    Location:
    Yakima WA
    You must realize that while you will minimize friction loss over a long distance, you can only get a finite volume of water through the original 3/4" pipe so the number of sprinklers you can operate one any one zone will be limited to that.
  5. ye

    ye New Member

    Messages:
    7
    Sure

    My house line is 3/4", so the only way to improve that is upgrade the service. As to the limitations - this is not a simple thing, as many plumbers might think. I have background in physics, and I know a lot about that. It is not just diameter that limits the flow, it is also the length. So, by going up to 1" - I will have significant impact on the losses of flow (less loss) due to friction on the long runs, which I'll have longer than the one my main house line has from the city main to my house. So from that prospective - I actually know the answer better than any forum can give me. What I was worried about, is if anyone with practical plumbing/irrigation experience knows about a step-up to be frequently associated with water-hammer... This is something that is hard to impossible to analyze theoretically, so that's where I need some practical advice.

    Thanks for responding.
    Last edited: Jun 1, 2008
  6. ye

    ye New Member

    Messages:
    7
    What I get from my 3/4" house line is about 12GPM, meaning I can have up to 8GPM on each valve, and going 1" won't increase that, of course, but will minimize the decrease over 150' run...

    I was also wondering about blazing end-of-lateral-line drain - is it worth it? Could you kindly respond to that?
    Last edited: Jun 1, 2008
  7. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,347
    Location:
    Yakima WA
    I have no idea what blazing the end of the line means.
  8. ye

    ye New Member

    Messages:
    7
    It is not "blazing the end of the line". It is a product sold by the company named "Blazing" called "end of lateral line drain". It's like any line drain plug, except: 1) it is combined with the 90deg elbow and adaptor from barb to thread (very convenient). 2) most importantly - it has this little ball in it, and when the water is turned on for a few seconds the ball dances creating turbulence, which flushes out any sediment from the filter, thus guaranteeing it "will never clog"... Apparently - this thing is forever! See here for instance http://www.sprinklerwarehouse.com/ProductDetails.asp?ProductCode=HP1700 . So I'm trying to see if anyone used it and could tell if it's as good as pitched. They only sell 1" barb to 3/4" thread, 3/4" barb to 1/2" thread. If I were to have these for every single sprinkler - I have to run 1" all the way to all 3/4" sprinklers, and 3/4" to 1/2" sprinklers... That sort of breaks conventional wisdom, and I'm wondering if it is worth doing that.

    Thanks for responding!
    Last edited: Jun 1, 2008
  9. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,613
    Location:
    Cave Creek, Arizona
    water hammer

    Water hammer, if it is going to be a problem, occurs in front of the solenoid valves, not after them so it makes little difference what size pipes you use to the various zones. And unless your velocity is at the maximum point in the flow curve when it is impossible to flow any more volume because the velocity would try to create more pressure restriction than is available, increasing the pipe size gives marginal improvement.
  10. ye

    ye New Member

    Messages:
    7
    Great!

    Thanks - this is what I needed to hear.
    Still curious - ever heard of those dancing balls in Blazing's drains? I'm really wondering if they are worth all this trouble...
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