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Water hammer issue

Discussion in 'Irrigation' started by mitchgo, May 6, 2011.

  1. Kiril

    Kiril LawnSite Fanatic
    Messages: 18,334

    I don't know how they technically work (the unit I linked to), however I don't believe they are like a water hammer arrestor with an air chamber, which I believe can fill with water under certain circumstances.

    Your on/off test should be conducted by allowing the lines to fill completely, .... shut the valve off and allow enough time for any pressure transients caused by the closing valve to dissipate, then fire it up again. If the hammering is just as severe then I would be suspecting some serious line drainage/leak, or there is trapped air. There may be other causes as well, but those would probably be the first I would consider, especially given the size of that line.

    If you are going to replace the valve, might as well put in a Griswold DWS. This will help to control hammering from both opening and closing the valve.
  2. ASI

    ASI LawnSite Member
    Messages: 64

    Mitchgo I believe that you answered your question yourself. ISOLATION!!! If you want to fix this fast and easy all you need to do is isolate the water entering the house and the irrigation system. Install a brass spring loaded check valve just below the PVR .Putting it there will make the job easy because the PVR will have a union so you can cut the pipe and solder in a check and screw union back on. Or you can buy a check valve that fits inside the union of the PRV. I have used two of these in union check valves where cutting into the copper to place the check in the right place would be a pain. If I remember correctly they cost about $40.00 and take two minutes to install. Open union drop the check in- close union and hang tag for others to know it is in there.
    Here is a link to the manufacture. http://www.checkall.com/valvestyles/UIV/UIV.htm
    Note: you need to know the model and manufacture of the PVR to check the angle cut of the union to insure it will fit. If the angle is different the union will not seat correctly.
    And from my experience water hammer arrestors are a waste of time and money. If anybody has ever installed one that worked please post a reply. I have heard of using expansion tanks instead of water hammer arrestors but have never seen one used that way.
    Isolation of the house water and irrigation system is the key to stopping any noise in the house. I have fixed a few dozen houses with all kinds of pipe banging and noises and the check valve worked every time.
    I hope that helps.
  3. Tom Tom

    Tom Tom LawnSite Bronze Member
    Messages: 1,281

    nailed it right there
  4. mitchgo

    mitchgo LawnSite Silver Member
    Messages: 2,922

    Haven't been back out there.

    But I think there would still be a sudden inrush flow that would cause the hammer

    Using the flow control would be better to diagnose
  5. Mike Leary

    Mike Leary LawnSite Fanatic
    Messages: 23,097

    Ditto.......I love flow controls.
  6. mitchgo

    mitchgo LawnSite Silver Member
    Messages: 2,922

    Just wanted to let others know that after my own theory on this and ASI pretty much confirming my idea..

    This works- Installing a check valve after the POC of the irrigation system to isolate the house line and irrigation line

    I have now dealt with 7 systems with water hammering inside the house ONLY when the zone is turned on and have installed check valves with all 100% success... This only works when there is noise inside the house when the zone turns ON..

    When it turns off, this is a completely different situation
  7. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,261

    If you install a check valve in the house supply, you also have to install an expansion tank for the water heater, if one isn't already in place. Bad juju if you don't.
  8. Kiril

    Kiril LawnSite Fanatic
    Messages: 18,334


    Thing is, you haven't solved the hammer problem, just masked it. Also, check valves aren't built to arrest water hammer .... expect premature failure.
  9. Fireguy97

    Fireguy97 LawnSite Senior Member
    Messages: 394

    Expansion tank is only needed if you install a check valve at water point of entry into home. If a check is installed from home to irrigation, its not needed.

  10. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,261

    That is not the remedy mentioned here. They installed a check in the line feeding the interior plumbing (keeping it from moving to the sprinkler supply when the zone is opened) and when you do that, the expansion tank is required.

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