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Water hammer issue

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

  1. Fireguy97

    Fireguy97 LawnSite Senior Member
    Messages: 394

    My read on mitchgo's comment was that he is installing a check at the POC of the irrigation system so that the irrigation system would isolate the house line and irrigation line - like he said. I missed the part where he said that he was installing the check on the main feeding the house.

  2. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,229

    I think that some of these situations might be worse nowadays, with water heater expansion tanks becoming commonplace, which easily makes for a monentary backflow from tank to POC when a zone is opened.
  3. AI Inc

    AI Inc LawnSite Fanatic
    Messages: 26,606

    You got that right. I dont think I ever had to deal with water hammer on a house that didnt have a expansion tank on the boiler.
  4. ASI

    ASI LawnSite Member
    Messages: 64

    I am glad you were able to fix the problem. The check valve fix has always worked for me.
    What kind of check valve did you use?

  5. Kiril

    Kiril LawnSite Fanatic
    Messages: 18,334

    What is so funny about what I said ASI? Both statements are 100% correct.
  6. Mike Leary

    Mike Leary LawnSite Fanatic
    Messages: 23,089

    :laugh::laugh::laugh::laugh: Mom always said you had a rapier wit.
  7. mitchgo

    mitchgo LawnSite Silver Member
    Messages: 2,921

    Just a brass single way check valve


    In every single situation other then this post I have seen with hammer noise coming around or from the PRV at the house which is typically right after SOV for the house. This still remains only when the system is turned on. Before I suggest anything I check to make sure All valves are fully opened

    In these cases I've always recommend for the PRV to be replaced by a plumber and then to also have us install a Check Valve after the POC tee which is almost always at the water meter ranging typically 50-300' away. In my opinion I believe the PRV does like water flowing backwards through it and after years of it doing it it starts to fail the PRV.

    In the situations I have dealt with. I have seen some systems with a couple irrigation valves cause the hammer noise to every valve cause the hammer. On the ones with every single valve- I went to the smallest zone and then turned off just about every single head to get a gpm of maybe 2-4 gpm.

    Although it's less I still hear the hammer with the sudden inrush..

    I'm sorry but a $2-300 basically for sure fix after the poc is a much more justifable thing to do then tell the customer oh.. Well now we have to install all sams, completely redesign the zone .. replace the pipe in order to fix this. For every zone.

    I'll keep in mind and understand that it isn't the best solution , but it's a good quick fix. I do tell every customer that this may or may not work but i've had success in the past. The first 3 clients I offered to do it for free and then if it works charge half the normal charge.


    Of course I don't want to be screwing up anything inside the house

    Can you explain on how installing a check valve after the point of connection for the irrigation system on the service line will affect the water heaters expansion tank? If it does have one or not? I'm no expert with them-
    Last edited: Sep 11, 2011
  8. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,229

    I don't think you made it clear that there was an expansion tank (or PRV) ~ the caution is for adding a check (or a PRV) without the heater getting an expansion tank at the same time. (although, most PRVs have an internal bypass to let excess downstream pressure bleed back through the device)
  9. Kiril

    Kiril LawnSite Fanatic
    Messages: 18,334


    The point I am making here is, it is not a fix for the hammer. Just because you aren't hearing hammer anymore doesn't mean the hammer isn't still occurring .... i.e. you have masked the problem. If anything, you have made the downstream (of the CV) hammer worse. I think it is important that people understand this. Beyond that, unless the check valve is designed to handle shock loads (most aren't including the one ASI linked), they will fail prematurely.
  10. ASI

    ASI LawnSite Member
    Messages: 64

    Any time you put a device that does not allow the flow of water back to the water main it is considered a closed loop. Installing a check valve, backflow, water meters with check valves or PVR in-between the main and the hot water heater will cause thermal expansion in the pipes. Closed loop and no tank you can expect the weakest link in your plumbing to let lose.

    I thought you were kidding.:confused:
    I believe there is a misunderstanding on the use of the check valve. I responded to Mitch post because I thought I could help. His description of what was happening was very close to what I have seen many times and the check valve had always worked. The first time I tried to correct the problem I wasted a lot of time by changing things and nothing worked. The check valve isolates the water in the house from irrigation system. There is no water hammer or stress on the check valve that would cause damage or failure. The check valve does what it is designed to do.It only allows the water to go one way.

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