sprinkler main line

Discussion in 'Irrigation' started by bayaa, Jan 20, 2002.

  1. HBFOXJr

    HBFOXJr LawnSite Bronze Member
    Messages: 1,712

    OK Tony, you can go to 10 gpm on the 3/4 if it is class 200. Over that you'll exceed a 5ft/sec velocity. Velocity, thats a big word. Tony do you think some people can say velocity? If your sched 40 3/4" your down to 8 gpm to stay under 5 ft/sec.

    I think valve closing is related to manufacture. Some are just better than others. Some manufactuers recommend closing the "flow control" till head performance visually diminishes and then open up one turn.
  2. SprinklerGuy

    SprinklerGuy LawnSite Bronze Member
    Messages: 1,778


    Hey you're right...it is a big word. Like you have said before Harold, should be careful who we give advice to here and what advice it is. Without the proper background in hydraulics and system design etc......information given in small bites like we sometimes do here....can be very dangerous.
  3. bayaa

    bayaa LawnSite Member
    Messages: 43

    So is ok to use one inch vavles and use 3/4 inch laterals
  4. HBFOXJr

    HBFOXJr LawnSite Bronze Member
    Messages: 1,712

    What's your Calif lic number? You are licensed, right?
  5. aquaturf

    aquaturf LawnSite Member
    from MA
    Messages: 28

    Hey Bayaa,

    No - don't use 3/4" line. In fact, you may want to walk away from the job, and do some easier ones before you try to tackle pressure like that. However, if you decide to continue:

    Given your pressure of 110, which I am assuming is the static pressure (no water running), you should use 1" laterals. Of course, once you flow water, the pressure will drop as more water flows (residual pressure). You should know what your residual pressure is at your desired flow rate. In other words, if you are looking for a flow of 10 gpm, what is the pressure (psi) at that flow?

    I am no engineer, and certainly not as talented as our two egotistical ("big word") professors on this board, but I will give you the best advice that I can. If you use 3/4" pipe you may have problems with high velocity, which can cause water hammer when the zones open and close. The larger diameter your pipe, the less velocity you are likely to develop, everything else being constant. Thus, I would suggest 1-1/4" mainline with 1" laterals so that water hammer will be less of a problem. Remember, water hammer is a chronic problem - your system may be working fine when you leave the job, but hammer can slowly weaken pipe and fittings in the future months and years.

    Like I said before, your pressure of 110 psi is of concern to me, and is quite high for residential. You may want to use some type of pressure control device, I have never used them.
  6. HBFOXJr

    HBFOXJr LawnSite Bronze Member
    Messages: 1,712

    You need design and engineering training before handing out advice. If you can't run with the big dogs, stay on the porch!
  7. bayaa

    bayaa LawnSite Member
    Messages: 43

    thank you for the advice it has helped a lot. Also to the other members of this fourm thank you for some of your advice.
    I will for sure use a pressure reducer and I'm trying to learn more about water hydruils that is why go to this fourm. Sometimes you got to learn as you go to pay the bills .
  8. HBFOXJr

    HBFOXJr LawnSite Bronze Member
    Messages: 1,712

    2 or 3 days of basic design is all you need to get started . You won't have it memorized but you'll be aware of all that goes into smaller residential & commericail systems. It takes about 5 years to make a good sprinkler man around here. Thats because all the little things change from job to job and you need 5 years exposure to cover a variety of stuff. Don't tell us you can't take the time. If your committed you make the time.
  9. HBFOXJr

    HBFOXJr LawnSite Bronze Member
    Messages: 1,712

    did you get the Hunter design book yet. Are you licensed?
  10. Chuck Sinclair

    Chuck Sinclair LawnSite Senior Member
    Messages: 336


    Check this out see if it helps you Learn:
    Irrigation Manual

    BTW are you licensed? you need a C-27 Contrators license in California to do irrigation.

    YES i am Licensaed #798016

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