flow charts

Discussion in 'Irrigation' started by woodlawnservice, Feb 23, 2013.

  1. woodlawnservice

    woodlawnservice LawnSite Senior Member
    Posts: 762

    If say I do loose 15 lbs over the 400ft... and I have a static of 90psi at meter... I need a pressure reducer anyways but would u leave the pressure on the high side to compensate for the Loss at the end of the run... or u think I will have issues with water hammer and that jazz...
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  2. Mike Leary

    Mike Leary LawnSite Fanatic
    Posts: 21,925

    You THINK you have 90 psi (so say the purveyors, who are liars), then you deduct at least 10 psi for the backfow, and another 10 for ancillary. The other lag is 90 psi means dick unless you can measure gpm at the source, as well as computing what you need at the last head after taking pressure loss calculations. Do the math; you may have 60 psi if you're lucky, but we have no clue what gpm is available. Hydro zones/sun/shade, etc. are very important, but unless you know the physical restraints of the supply system, you are pissing up a rope. :drinkup:
     
    Last edited: Feb 24, 2013
  3. woodlawnservice

    woodlawnservice LawnSite Senior Member
    Posts: 762

    Yep.. do u prefer to upsize pipe to get more gpm and.more rotors on a zone or prefer small pipe (1") and just do less rotors? Or do smaller pipe with more rotors and.nozzle them down and have longer run times? The price difference between the two sizes 1.25 and 1 are pretty big around here... you get so muh more flow with the 1.25 though. I prefer less run times and put more water out quicker... soaking in the ground and runoff isn't an issue with this soil...
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  4. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,419

    On a large system, you upsize the mainline pipe first. From source to the greatest distance, the pressure loss should be less than 5 psi, in order for you to obtain uniform performance from zone to zone. Also, a long mainline run greatly magnifies the effects of water hammer, to the point where you can blow apart the zone valves at the end of the line.
     
  5. woodlawnservice

    woodlawnservice LawnSite Senior Member
    Posts: 762

    Well I will.have a master valve if a problem.ever does blow a mainline but I don't want that of course...the way this land is 150 wide 400 deep...there's not many options on how I can run this mainline to shorten it unless I want run my laterals longer which I don't think makes much sense either...
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  6. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,419

    Valves malfunction. You don't design a system whose integrity depends on a master valve.

    Water hammer is a function of water velocity and pipeline length. It doesn't take even a hundred feet of length to make for damaging hammer. Since you can't shorten the mainline length, you slow down the water velocity. Slow it way down.
     
  7. Mike Leary

    Mike Leary LawnSite Fanatic
    Posts: 21,925

    You will never,ever, get more gpm than the service provides, nor will you get any more pressure. You design for what you got; then deduct for the friction loss and the demand of the zones, and, bingo, there's your system. Easy, we do it every day. :clapping:
     
  8. woodlawnservice

    woodlawnservice LawnSite Senior Member
    Posts: 762

    Yes sir so service being 1" and looks like ill.need to slow it down so upsizing isn't an option... may even.need to go up to 1.5 in. Need to run. Velocity numbers to make.sure Im not over 5...
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  9. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,419

    With 90 psi street pressure, and 400 feet for the mainline, you want to forget about the usual velocity guidelines, and go even slower.
     
  10. Mike Leary

    Mike Leary LawnSite Fanatic
    Posts: 21,925

    IF is the question. PSI must be measured, as well as flow output. Anything less is lumpy gravy and guaranteed to fail.
     

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