Spacing for 2 acre irrigation.

Discussion in 'Irrigation' started by jcom, May 6, 2007.

  1. jcom

    jcom LawnSite Senior Member
    Posts: 791

    We are preparing a design for irrigating approx. 2 acres from a river source.

    Using an Aermotor 3 hp pump at 55-60 gpm. 2" mainline

    We keep our regular spacing for our Hunter PGPs under 35'.

    Is it possible to lengthen this out with the above specs for less material.

    Thanks for the opine!

  2. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,799

    Is this the same one you posted about a year ago?

    What pressure are you expecting from this pump?
  3. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,799

    I'd also go to a 2.5 inch mainline, as 60 gpm on 2" is a hair over the 5 fps threshold.
  4. 2" main with 1 1/2" valves with 1 1/2" laterals stepped down to 1" then 3/4" spaced at about 42'- 45' with PGP's with # 9 nozzles and 9 or 10 heads per zone should work just fine.
  5. jcom

    jcom LawnSite Senior Member
    Posts: 791

    Yes, this is the same one. We are expecting 45-50 psi from this pump after conversations with Aermotor co..

    I was planning on looping a mainline, using 2" valves, going to 1" laterals as needed for gpm capacity. Est. 4 -1" laterals per 2" valve.

    We don't step our regular 1" installs down to 3/4" and were not planning on it here.

    Thanks again for the help on this one.

  6. jcom

    jcom LawnSite Senior Member
    Posts: 791

    Wouldn't 10 heads with #9 (4gpm) nozzles be underutilizing the capacity of the pump? I thought we wanted to stay withing 10 % of the capacity with the zones.

  7. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,999

    How about you actually run the pump and confirm the performance figures? Then you can worry about head spacing.
  8. #9 @ 45-50 psi is about 5gpm, Rain Bird PEB's 1 1/2" and 2" valves use the same size diaphragm so I would just use a 1 1/2" since it is rated for 100+ gpm ....
    at 50 pgm your pressure loss would be 2.2 on a 1 1/2" and on a 2" would only be 1.2
  9. txgrassguy

    txgrassguy LawnSite Gold Member
    Posts: 3,083

    Depending on the factors already mentioned, you are not allowing for variances in climate, wind, soil conditions, etc.
    You could very easily end up spacing the heads too far apart and end up with dry spots at the terminance of the coverage areas.
    What is the intended purpose of the site, residential, commercial or athletic fields.
    Traffic patterns on the site will also dictate head spacing as a higher traffic pattern equals accelerated wear patterns absolutely necessitating more complete coverage.
  10. jcom

    jcom LawnSite Senior Member
    Posts: 791

    This is homeowner and low traffic area on 95 %.

    I like WB's input. Better have the pump hooked up and put my psi gauge on and see what flow I can actually achieve at the desired psi.

    Thanks for all the input.


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