Determining FLow for New Install

Discussion in 'Irrigation' started by Planter, Nov 13, 2003.

  1. Planter

    Planter LawnSite Member
    from Utah
    Posts: 214

    What method do you guys use to determine flow on a new install before you lay it out? I've seen many guys do a static pressure test, tap a 1" line into it and call it 15 GPM. I've seen the open the valve on the house and flow the 5 gallon bucket with the stop watch method. Any tricks to the trade here?
  2. Ground Master

    Ground Master LawnSite Senior Member
    Posts: 505

    There are charts that you can consult.

    In my area most homes have a 5/8" meter and 3/4" mainline which provides for 10 gpm safely.

    Sounds like you have a 1" main and meter? You ought to be able to get 18 gpm safely.

    The bucket method will not give you accurate results.
  3. MikeK

    MikeK LawnSite Member
    Posts: 145

    Don't ever guess on the flow before you do an install. Know exactly what you will get.
    Using a flowmeter off of the water faucet is Ok but it tends not to be too accurate. Especially if they have one of the screw on type backflow preventers on the faucet.

    On Every bid I give, I just take the static pressure, check out the meter in the basement and use the Hunter Design caculator available from thier website. It's dead on accurate and very useful.
    It's no problem to use since I have the laptop mounted in the truck anyway.
  4. turfman59

    turfman59 LawnSite Senior Member
    Posts: 801

    If you can open 2 or 3 hose bibs do it like this

    put a pressure guage on one hose bib and open it make a note of the static pressure for your file

    open the other hose bib wide open and go back to the guage and see what the dynamic pressure is...

    If there is another hose bib open that one and go back and check the dynamic pressure one more time, if it hasnt dropped from the first one, you can safely calculate gpm from the two hose bibs. If it has dropped you probably have max out the Gpm...

    Static pressure is good to check just for a base line reference.
    I still would flow charts that have all the friction losses and design it right down to the last sprinkler head that is farthest away from the point of connection....

    If you still are unclear you need more education to do the design...

  5. ldr1976

    ldr1976 LawnSite Member
    Posts: 14

    I use a hose rigged up with ldn nozzles for cneter pivot irrigation. You farm raised people will understand that. Check it with a 5 then 10, 15,20,25 nozzle making note of each pressure at each nozzle. Then i have a chart that tells me what each nozzle is putting out gpm at that given pressure. Then i graph it on graph paper with pressue being vertical on the gragh and gpm being horizontal. Then you can intersect the two points for whatever pressure you would like to maintain on the system and you will know exactly what your usable gpm will be.
  6. jwilson32

    jwilson32 LawnSite Member
    Posts: 64

    Ground master is right on. The newer homes here have 1&1. Wich i can run 18gpm. 6 rotors or 11 sprays.

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