Water Hammer

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Tindel, Dec 15, 2012.

  1. Tindel

    Tindel New Member

    Messages:
    4
    Location:
    Colorado
    Hi - great forum - hopefully I can get some help too...

    I've had some water hammer issues for about a year now. I've tried many different things. I believe my issues are a function of a new water tank being installed in the neighborhood about the same time I started having issues. Shortly thereafter, I bought a water hammer arrestor and installed it in the bathroom where the toilet seems to cause the most banging of the pipes. This helped for a while (about 6 months), but the arrestor doesn't always stop the banging anymore, I am assuming the internal bladder is starting to weaken.

    Today I checked the house pressure at the outdoor water lines and they read ~95psi. I'm thinking this is too high from what I researched, and could be what is causing my water hammer issues, so I think I may need a pressure regulator on the water main coming into the house. Does this seam like a reasonable conclusion? Any other ideas?

    Also, I've been looking at these and trying to figure out which one I need for a house with 3 baths, kitchen, and laundry room - I can't tell much a difference except for how they look. http://www.homedepot.com/webapp/cat...02721939&prodComp_3=202721942&N=5yc1vZ4n3Z57z

    Finally, I have a pressure regulator in the basement keeping things to 55psi in the kitchen and laundry... should I remove it and install it on the water main - saving me some money... or just put one of those shark bite regulators on the water main, just inside the house, set it for 60 to 65 psi, and be done with it? Can I do that, or will I have other problems?

    Why didn't 'they' just put the regulator on the water main the first time? - The main is only 3 feet away from where they did install it. Doh! oh well. :p

    Thanks for anyone willing to help.
  2. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,387
    Location:
    Yakima WA
    You will need two things. A pressure regulator and a thermal expansion tank. Household water pressure can have quite a range and be acceptable, but should not exceed 80 psi, but that is still more than necessary. Anywhere from 40 to 60 psi is plenty of pressure. The reason you need a thermal expansion tank is when the water heater does it's job and heats the water, hot water expands. Since water can not be compressed, the expansion has to go somewhere. Before the pressure regulator is installed, this expansion is absorbed by the city water main. However, the PRV has a check valve built into it that prevents this from happening. So the expansion build pressure in the water heater and trips the T/P safety valve to prevent the heater from exploding. Now, the volume of water isn't huge, but it is enough to create a problem. The expansion tank provides a temporary "home" for this expansion. The PRV can be installed anywhere, but in my opinion it should be inside the house where it is easy to access. It is installed in the cold water supply between the PRV and water heater. The high pressure you have is hard on toilet flush valves, dishwasher valves, and clothes washer valves as well, so it should regulate all of the water with the exception of outside hose bibs. The air pressure in the expansion tank should be balanced to equal the PRV setting. Easy to do with a pressure gauge.
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,270
    Location:
    New England
    You should also check the pressure - your existing regulator may be shot.

    Water hammer happens when you stop the moving water column fast - the more common valves that open/close fast are toilet valves, washing machines, dish washers, ice makers, humidifiers, i.e., anything with a fast acting (often solenoid) valve. The intertia of the fast moving water hitting on the now closed valve pushes the pipe and it may then hit something, causing the noise. It's not good for the valve or the pipe, since it is being moved, it may rub on things and eventually wear a hole, not counting the annoyance of having to listen to it. High water pressure makes this worse, since the water moves faster through the pipes, it has more kinetic energy (inertia), and can hit things harder. SOme arrestors are better than others, but any normally would last longer than months - they typically last many years. A simple T with a capped stub of pipe quickly fills with water and becomes useless, and is never a good solution.
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,056
    Location:
    Cave Creek, Arizona
    If you are asking which of those regulators I would install, the answer would be 'none of the above'. Why they didn't install a PRV on the main line is something you would have to ask them because a plumber would NOT normally have done that. Logically, that regulator should be for a smaller pipe than your main line, so it may not transfer to it.
  5. Tindel

    Tindel New Member

    Messages:
    4
    Location:
    Colorado
    Hmmm... I don't think I asked my questions very well... so let me try again.

    Here is a rough schematic of my COLD WATER LINE:
    The items in black are existing items,
    The items in red would be new installations.
    ColdWaterSchematic.jpg

    My questions are:
    • Can I have two regulators in-line? One with higher pressure - 65psi, maybe, and the existing with 55psi.
    • Do I really need the expansion tank - I haven't had it since I moved in 5 years ago.
    • Are any of the attached shark bite regulators (in my first post) adequate for regulating my entire house?
    • Should I reuse my existing regulator and put it in the new regulator location and install the expansion tank where the exiting regulator is at?
    • Why shouldn't I have a regulator on my garden hoses?
    • Does my measured pressure at my garden hoses (95psi) seem like excessive pressure?

    Thanks,
    Tindel
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,270
    Location:
    New England
    Code requires in-house water pressure to be limited to 80psi...an inspector when it came time to sell might give you grief, and some valves do not work well at that pressure. Many people like to place the PRV after the takeoff to the outside hose bibs - it does make watering the lawn easier (it's still against code if the pressure is over 80psi).

    A PRV makes the system 'closed', and that means that when you replace heated water in the WH with cold, then it gets heated, it will expand. It cannot leak back into the main line because (if the PRV is working right anyway), it's a one-way valve, so it must leak out somewhere. You might find that that's happening slowly in a toilet, or some other place, but if they all are working really well, the pressure will rise enough where you'll get a release from the T&P valve on the WH. This valve opens at 150psi, and that is easy to attain in a closed system when you heat water. So, starting with high pressure then heating water, you're putting lots of stress on things. This increases the likelyhood as the faucet hoses age along with the washing machine and maybe icemaker supply lines will blow out. You really don't want to risk it. If you have pex water lines, they are actually absorbing the expansion by bulging. It's not a great scenario...a closed system must have a means for expansion, and that's an engineered expansion tank.
  7. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,387
    Location:
    Yakima WA
    One PRV is enough. Set it at 60 psi and your good to go, but do heed our warnings about the expansion tank. Have you a back flow prevention device in the irrigation side? They required although some places do not enforce the law on them. Not only should there be one, but it should be certified annually by a certified inspector.
  8. Tindel

    Tindel New Member

    Messages:
    4
    Location:
    Colorado
    Okay - I've got the memo on the expansion tank -

    What about some of my other questions?
  9. Tindel

    Tindel New Member

    Messages:
    4
    Location:
    Colorado
    Well - I moved my PRV to supply the entire house. I also installed an expansion tank. Both are set to 55psi. My toilet valves seem to be much happier. I haven't noticed any water hammer in the last hour since I fixed it anyway.

    Gary - I'm 99% sure that there's a check valve on the sprinklers. It's a pretty bulky system.

    What's wrong with the website?
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