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Thread: irrigation flow rate/psi has me completely confused!

  1. #1

    Default irrigation flow rate/psi has me completely confused!

    Hi, I'm overwhelmed by all the calculators on the rainbird site and really need some help with some simple problems.
    Hope someone here can help.
    I'm in the process of having a well drilled and need to figure out how much water we use on irrigation, which isn't all that much.
    We run one short 100' length of 2" pipe with risers every 20' and I think 7/32 nozzles on the risers, totaling 6 risers. We move this line through the garden and yard in addition to some drip irrigation in the orchard.
    We also have some home usage on the same pump.
    How can I figure out the flow and psi we need to run this line optimally.
    Any Help, please?
    Last edited by madrone; 01-13-2009 at 09:15 PM.

  2. #2
    Sprinkler Guy Wet_Boots's Avatar
    Join Date
    Mar 2007
    Metro NYC


    You'd be surprised how difficult it is to quantify "some" ~ nothing prevents you from changing impact head nozzles, so you aren't locked into any particular flow. Think in terms of how much acreage you need to cover in what period of time.

  3. #3
    In the Trades Gary Swart's Avatar
    Join Date
    Sep 2004
    Yakima WA


    If there is an irrigation supply company in your area, take a scale drawing in to them. Often these companies will design a system for you at little or no cost providing you buy all of your supplies from them. It does get complicated as it is far more than just gpm and pressure. Length of pipe needed, elevation changes, number of sprinklers on a zone, and on and on. You might even find that a complete underground and automatic system would be feasible. Even if they charge for this service, it would be a good first step.

  4. #4


    For most situations, if you installed a pump that would produce 10-20 Gallons Per Minute (GPM) and 65-100 static PSI of pressure that would be PLENTY.


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