GPM Question

Discussion in 'Irrigation' started by grassassassin, Mar 21, 2006.

  1. grassassassin

    grassassassin LawnSite Member
    Posts: 57

    I went to a house today to take in all info. Pressure is 54. Gpm is 4.28. Am I doing something wrong? Surely it has more than 4 gpm. Method to determine gpm was a 5 gallon bucket. It took 70 seconds to fill up from the outside spicket. 300/70 = 4.28. Any help would be appreciated. Thanks in advance. By the way, if this is correct how do I go about designing a system that is on over 1.5 acres?
     
  2. BSME

    BSME LawnSite Senior Member
    from Midwest
    Posts: 829


    was that the pressure while you were filling up the bucket or was it static?

    since the spigot is probably a 1/2'' line you would get more gpm out of a 1'' line when you actually made the plumbing tap
     
  3. grassassassin

    grassassassin LawnSite Member
    Posts: 57

    the 54 psi was static psi. So a dumb question, how do I get a accurate gpm? I know that a 1 inch line will supply more gpm with less psi loss. So yes it is a great idea to come out with a 1 inch pipe, but how do I know what my gpm will be and my psi so that I can design the system? Remind me why I am getting this info from the spigot? Thanks for your replies.
     
  4. I usually check it at the spigot like you did...if it is between 4-6 gpm....and the pressure is decent while doing so....operating pressure is different than static....then you can pretty much figure that you will get what you should with a larger sized pipe.

    However......check the meter to see what size it is....you will be limited by the meter.
     
  5. grassassassin

    grassassassin LawnSite Member
    Posts: 57

    That's the other problem. I checked the meter and it says 5/8 and 3/4. Don't really understand that one.
     
  6. Flow Control

    Flow Control LawnSite Bronze Member
    Posts: 1,267

  7. Ground Master

    Ground Master LawnSite Senior Member
    Posts: 505

    what size is the service line to the meter?
    are you measuring the pressure after the pressure regulator?
     
  8. Critical Care

    Critical Care LawnSite Bronze Member
    Posts: 1,654

    Heh heh, you may also want to double check (no pun intended) to see if you have a double check valve assembly in line, or a PVB with a valve not fully open. Never know…
     
  9. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    Is there more than one hose bib? Attach your pressure gauge and then open the other bib and check your pressure. If your getting 4+gpm from a 1/2" hose bib and maintaining a decent operating pressure, then I would say you have the ability to put in a system. Your not going to be real productive watering 1.5A w/ a 5/8" meter, but you could design a system that would provide enough water to keep things "alive" during droughts and supplement normal rain in the spring and fall for a nice turf.
     
  10. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,799

    We've done a handfull of systems that only had 4-5 gpm to play with. Most were on real low output wells.

    The trick is small nozzles, lots of zones, and long watering times.

    We have one system that is rather large and runs from midnight to 8 am.
     

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