GPM Figuring

Discussion in 'Irrigation' started by RwADesigner, Feb 4, 2003.

  1. RwADesigner

    RwADesigner LawnSite Member
    Messages: 107

    I have recently ran into a client who isnt on a meter but has a direct connection from her home line to the main city water line. Her line is 3/4". I am use to workin with 1"-1.5" meters.

    I have a 55-60psi, could someone help me by telling me how i need to figure the gpm allowed per zone. Or what a safe gpm/zone would be to stay under. For normal commercial/resident...i go from anywhere to 20-35gpm...

    There is no slope..on site..
  2. turfman59

    turfman59 LawnSite Senior Member
    Messages: 801

    This is only a guess 13 gpm at the point of connection, before the backflow preventer. You should do a test with a bucket and stop watch, if you can open another hose bib do that also.....THIS IS A GUESS !!!!!!!!!! AQUA TURF will not be held responsible for the previous information, remember your the contractor in charge.
  3. RwADesigner

    RwADesigner LawnSite Member
    Messages: 107

    ya bruce.. gotcha

    i actually came up with i was close

    I think i can get more gpm if i increase the size of the pipe coming from the streat to house...from 3/4" to 1-1.5". Just need to check on it to see if it is permited....

    If i do 1" i can get it up to around 20
    1.5" i can get up to around 30

    would help me alot

    what do you think.....and no aqua turf isnt liable....
  4. RwADesigner

    RwADesigner LawnSite Member
    Messages: 107

    20 gpm on both..sorry
  5. devildog

    devildog LawnSite Senior Member
    from sc
    Messages: 270

    How do they turn the water off in an emergency or for plumning repair, is there a gate/ball valve in line?

    If your accustomed to 30 GPM, use that munber. Or 9 rotors with 3.0 nozzles, If you working with part circles and full's, you will have to adjust your nozzles for even precipitation rates.

    NO METER ?
  6. DanaMac

    DanaMac LawnSite Fanatic
    Messages: 13,209

    Most our lines here are 3/4". I usually design a system at 12 gpm and have had no problems. I have gone a little higher at times as well. A couple areas south of town had the same thing with no meter. They paid a flat rate for water. And there was a ball valve in the basement for on/off to the house.
  7. HBFOXJr

    HBFOXJr LawnSite Bronze Member
    Messages: 1,712

    To stay under the magic 5 ft/sec velocity in 3/4 class 200 pvc you can only about about 10 gpm. On the same service here with meter I'd max at 10 most of the time.
  8. turfman59

    turfman59 LawnSite Senior Member
    Messages: 801

    Just remember that when you run that larger 1" or 1 1/2 " that you will create a lot of velocity in the 3/4'" copper service that remains, depending on how many feet that is left is the critical question. Sometimes it can be as high as four times the friction loss. Maybe Harold can speak to this?
  9. turfman59

    turfman59 LawnSite Senior Member
    Messages: 801

    Yeah Gotcha Back !:D

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