Pressure and GPM - Designing System

Discussion in 'Irrigation' started by jbell36, Sep 24, 2012.

  1. jbell36

    jbell36 LawnSite Bronze Member
    from KANSAS
    Posts: 1,258

    this is exactly what i was thinking, but i wanted to ask because i'm usually wrong...on this particular system we have 7 heads on two of the zones and i can guarantee you we could put another 7 on...you can't even push the head down with your foot...we didn't design the system, but we did renovate it...the issue is it's on a huge hill and years ago when the house was first built the builder didn't backfill or pack the hillside properly and there was a landslide...i didn't find this out til later, because the design of the system made absolutely no sense, but when they told me this it all clicked...there was 40' of swing pipe at the bottom coming up at a 45 degree angle to compensate for the pipe/heads that slid down the hill...one lateral was only half way across the hill, so we had to install like 100' or something like that just to complete the system...

    anyways, i was thinking while i was there how i would have designed the system knowing it was a 5/8 meter and knowing there is 90 psi...it just makes more sense to me that if you are able to put more heads on a zone that will cover adequately then why not...i just figured i would ask just in case there was something i didn't know about that i would be doing wrong
     
  2. muddywater

    muddywater LawnSite Bronze Member
    Posts: 1,813

    That was before i figured out u have to hold an iphone sideways to take a pic!
     
  3. muddywater

    muddywater LawnSite Bronze Member
    Posts: 1,813

    If it is a new neighborhood, i usually try not to max out gpms. Also keep in mind you lose/gain a 1/2lb of pressure per foot of rise/decline.

    And on a long pipe run to the backyard you are going to have some pressure loss if it is 1" pipe. So if you are running 7 heads with great pressure right at the meter, then try to do the same 200' behind the meter and up an incline you could have a problem. I always try to be conservative... keeps me out of trouble and leaves the option to add a head in the future.
     
  4. jbell36

    jbell36 LawnSite Bronze Member
    from KANSAS
    Posts: 1,258

    yeah this is all down hill from the meter,thanks for bringing that up, didn't think about that...
     
  5. greenmonster304

    greenmonster304 LawnSite Gold Member
    Posts: 3,014

    I used to have a chart that listed static pressure, meter size, and service line size. Using those numbers it would tell you the gpm. I can't for the life of Mencius it now though.
    Posted via Mobile Device
     
  6. 1idejim

    1idejim LawnSite Fanatic
    Posts: 8,849

    If you are being conservative use 0.433 per ft. instead of .5

    6.70 psi per hundred ft. difference
    Posted via Mobile Device
     
  7. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,298

    Careful man, you might upset boots. :waving:
     
  8. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,450

    Arrrrrgh, I can't find it on me slide rule.
     
  9. muddywater

    muddywater LawnSite Bronze Member
    Posts: 1,813

    You just had to google that didnt you
    Posted via Mobile Device
     
  10. 1idejim

    1idejim LawnSite Fanatic
    Posts: 8,849

    Nope, i am not an internet contractor.

    Rule of thumb is 2psi per 5 ft
    Posted via Mobile Device
     

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