Water Hammer

Discussion in 'Irrigation' started by itteitj, Jul 26, 2006.

  1. itteitj

    itteitj LawnSite Member
    from RI
    Posts: 74

    How do you deal with water hammer during irrigation cycle and specifically when system changes zones.
    Tom
     
  2. lawnmaniac883

    lawnmaniac883 LawnSite Silver Member
    Posts: 2,613

    You put bigger pipe in that will flow the amount being demanded :confused:

    If you get water hammer when the system changes zones then you are probably flowing more water than the valves/pipe are rated for.
     
  3. PurpHaze

    PurpHaze LawnSite Fanatic
    Posts: 5,496

    I'd look at the valves also. If they can't handle the PSI/GPM then they may be closing too fast/slow with the diaphragm fluttering. If the valve has a flow control on it then sometimes this can be tweaked and the problem is solved.
     
  4. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,794

    Water hammer is caused by excessive water velocity, usually because the mainline is sized too small.

    You can adjust the flow control like Hayes suggested, think of like tuning a carbeurated, throttle it down until its a little too much, and then back it off a hair.

    Or you can install slow closing valves. A pressure tank helps too on pump systems.
     
  5. PurpHaze

    PurpHaze LawnSite Fanatic
    Posts: 5,496

    I believe most (if not all) irrigation valves are designed as "slow closing" specifically because of potential water hammer problems. If they slammed shut then pipe could burst. Even the PVC ball valves we install on manual zones are kind of slow closing by water pressure. As you close them the water pressure resistance doesn't allow you to slam the last little bit down fast. I've tried it and even I can't close one of them down fast. :)

    Reminds me of a seminar I went to where the guy showed a sod farm where the main line was way undersized for the water they were using. Pictures showed all this 6" pipe laying on top of the ground as it burst. :dizzy:
     
  6. Dirty Water

    Dirty Water LawnSite Fanatic
    Posts: 6,794

    Those PVC ball valves are a biatch to close when they are in a 4" SDR-35 riser and down 18", and you don't have a key.

    There is one manual system we maintain that has regular brass ball valves with the long handles, you could really do some damage slamming those.
     
  7. PurpHaze

    PurpHaze LawnSite Fanatic
    Posts: 5,496

    The handles will rust off before you have any problems. Just ask our plumbers who love to install them. :laugh:
     
  8. Midlo Snow Maker

    Midlo Snow Maker LawnSite Member
    Posts: 183

    every zone or just one
     

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