how much water can i get through a 2" line??

Discussion in 'Irrigation' started by jonspolaris, Aug 15, 2001.

  1. jonspolaris

    jonspolaris LawnSite Member
    Messages: 130

    in my moms development they have a irrigation system. I have seen some of the zones in there that seem WAY too big. Some have over 35 heads. The supply is a 2" PVC line hooked up to a 8" street main. Im not sure about the pressure, but i would say it is good, sence they are close to the water tower.

    How much water should i expect to get through this size water line?? in gpm.

  2. HBFOXJr

    HBFOXJr LawnSite Bronze Member
    Messages: 1,712

    Flow should be restricted to approximately 55-60 GPM to keep the water velocity under 5 feet per second. Velocity over 5 feet per second can increase surge pressures dramatically if a valve closes too quickly. Pressure loss also increases. At 55 gpm in 200 psi class pipe, pressure loss is 1.7 psi/100" of pipe. Add 25 gpm and go to 80 GPM and the loss doubles to 3.4 psi/100'.
  3. racerdave

    racerdave LawnSite Senior Member
    Messages: 260

    The frictional piping loss stated by Harold assumes all pipe is in a straight line. Every 90 should count as ten pipe diameters. In this case that would be 20" per 90

  4. HBFOXJr

    HBFOXJr LawnSite Bronze Member
    Messages: 1,712


    So that would be about .028 psi per elbow, correct? Have you ever engineered or done a job where you needed to upsize pipe, add or upsize a pump, or plan pipe routing or installation technique diffferently because of the number of fittings?

    More common here is to add 10% to piping losses to account for fittings.
  5. racerdave

    racerdave LawnSite Senior Member
    Messages: 260

    yes. very much so. I have been installing complex processing systems for years (they are much more involved than a simple sprinkler system). Including fixing others mistakes. If I do make an error, it's going to be in my favor.:D

    My point is, everything must be taken into consideration when designing a Irrigation system. Down to the last fitting...

  6. greasemonkey

    greasemonkey LawnSite Member
    Messages: 57

    I hate fittings....they cost money, especially as the size gets bigger, they take time to install, and they are all potential points for leaks. As the flow goes up thrust blocking must also be considered. I try to avoid using fittings whenever reasonable. Calculating the friction loss on 110% of the actual linear feet of pipe works pretty well when designing :)


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