Low pressure on one zone only?

Discussion in 'Irrigation' started by A23, Mar 29, 2013.

  1. A23

    A23 LawnSite Member
    Messages: 72

    I've got a city park with 11 zones, all on municipal water supply. All of the sudden one zone only comes up to what I'm guessing is about half-pressure....only enough to raise the sprinkler heads up about a third-to-half way. Doesn't seem to matter too much if the valve is turned on manually, or by the clock, although the problem may happen slightly more often when turned on by the clock. It's a Hunter PGV valve, and isn't that old. I took the valve apart and inspected everything, which all appeared to be in good shape. There's no leaks anywhere to be found either.

    Anybody have any ideas or suggestions?
  2. 1idejim

    1idejim LawnSite Fanatic
    Messages: 11,358

    Do a 3 minute meter check of the zone, taking pics of the meter reading before and after running the zone.

    Divide the useage by 3 to arrive at yovr gpm.

    Add your nozzles for demand and you will know whether you have a leak or a restriction.
    Posted via Mobile Device
  3. DanaMac

    DanaMac LawnSite Fanatic
    Messages: 13,226

    Leak that just hasn't shown yet, tree root choking the pipe, issue with the valve that you cannot see, flow control closed part way. I'm leaning towards leak that hasn't shown itself yet.

    Turn on a different zone that is comparable in size (volume output), and check the water meter to see how fast the dial is spinning, and how it sounds. Then do the same with your problem zone. If the meter sounds like the other zone without a problem, and is screaming like there is nothing impeding the flow of water, more than likely there is no obstruction, and the water is leaking out somewhere. If the dial is slowly moving and you can tell that the water isn't moving very fast, there is an obstruction in the valve or in the pipe. Sometimes the water will follow a trench (even if it is many years old) and surface out somewhere far away from the actual leak or break.
  4. Sprinkus

    Sprinkus LawnSite Silver Member
    Messages: 2,322

    If a manual bleed, bleeding the valve to atmosphere and not just using the internal solenoid bleed, does not increase the zone pressure I would suspect a leak first.
  5. A23

    A23 LawnSite Member
    Messages: 72

    Ok good advice so far, thanks!
  6. RhettMan

    RhettMan LawnSite Silver Member
    from Texas
    Messages: 2,624

    Thanks :)

    why do a three minute meter check for a one minute calculation? vs begining at 60 seconds and stopping at 120 seconds


    thats one whole minute,


    its time to go flat :)
  7. RhettMan

    RhettMan LawnSite Silver Member
    from Texas
    Messages: 2,624

    dang, only took 20 minutes for that to no longer seem funny, I need a "delete my stupid sayings button"

    Goodweek yall, goodnight
  8. ArTurf

    ArTurf LawnSite Platinum Member
    Male, from Ark
    Messages: 4,470

  9. 1idejim

    1idejim LawnSite Fanatic
    Messages: 11,358

    No kiddin! Results of our input, regardless of the outcome, is the only payment the forum gets.
    Posted via Mobile Device
  10. A23

    A23 LawnSite Member
    Messages: 72

    Alright, sorry for the delay but here's the update :

    So I finally figured out what was going on, and I feel like a bit of a noob! :hammerhead: After searching for a leak, I replaced the diaphragm because I was sure that was it. Obviously, that didn't fix a thing.

    Now you have to understand that this is a pretty large grassy area full of St. Augustine grass, and there's way to many heads on the zone to begin with, but I wasn't involved in the install. So I did a walk around of every square inch of the area and found 3 heads with St.Augustine runners over the top of the pop-ups that allowed them to rise up just enough to have the water pour out from between the riser and the body, which are all basically leaks. I guess that those 3 issues, coupled with the over-abundance of heads on the zone, resulted in the low pressure situation.

    So that's the story. It was hard to find because there were not really any brown spots near the malfunctioning heads. It all works fine now, so mission accomplished. Thanks for the help everyone :waving:

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