Thunk....Water Hammer?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Cobra1365, Jan 8, 2021.

  1. Cobra1365

    Cobra1365 Member

    Joined:
    Feb 7, 2011
    Location:
    Delaware
    We had a new submersible well installed last January. Much better pressure and better, but not perfect water. I was going through RO filters sort of quick and ended up installing a Spin Down filter, a 10 micron and carbon Big Blue setup (also have a soda ash system for acidity).

    Lately, we’ve noticed a thunk in the far end of the house (bathrooms) when we turn off the sink or when the toilets stop filling. It also thunks there when the washer is running, even though the washer is on the opposite end.

    I don’t notice a thunk elsewhere.

    Is this something that installing an arrestor will help with?
     
  2. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    Yes. That is the classic case of water hammer, and arrestors at each fast valve helps.

    Actually the sink thing is unusual, in that normally sinks turn off slowly, unless you are closing fast on purpose for testing.

    If your new system is set for higher pressures than before, that could account for you getting more water hammer than before. Water is moving faster, and when it slams to a stop, bang.
     
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  4. Bannerman

    Bannerman Well-Known Member

    Joined:
    Mar 19, 2014
    Location:
    Ontario, Canada
    When the new pump was installed in switching from the jet pump to the submersible, were any additional check-valves installed in the drop pipe or directly before the pressure tank?

    Many pump installers install additional check-valves claiming they are needed. With a submersible pump, the check-valve is to be only located directly at the pump whereas additional check-valve(s) will often cause the issue you are experiencing.
     
  5. Cobra1365

    Cobra1365 Member

    Joined:
    Feb 7, 2011
    Location:
    Delaware

    No other check valves.

    The washer part is odd to me. I understand putting an arrestor at each toilet. But, where would I put them for the washer if it’s banging on the opposite end of the house? Or could I just put two in each distribution line under the house on the far end?
     
  6. Bannerman

    Bannerman Well-Known Member

    Joined:
    Mar 19, 2014
    Location:
    Ontario, Canada
    A hammer arrestor can be integral with the washing machine water service valves or installed on the feed lines just before or just after the service valves. https://diy.stackexchange.com/questions/88280/laundry-box-and-water-hammer-arrestor

    https://www.google.ca/url?sa=i&url=https://www.reddit.com/r/Plumbing/comments/as3ms9/do_hammer_arrestors_go_bad_washing_machine/&psig=AOvVaw0VjkhqkKozs8ZzJYOKZfUJ&ust=1610236148213000&source=images&cd=vfe&ved=2ahUKEwi-jpyew43uAhUKFlkFHV_GC-UQjRx6BAgAEAc

    Your pressure tank will also act as a large hammer arrestor, but it is not usually located too close to valves which quickly close such as the clothes washer or dishwasher solenoids or toilet fill valves.

    Hammer will cause a shockwave throughout the entire plumbing system. Depending on the plumbing configuration, what you are hearing at the far end, maybe because that is the end of the line and conditions are such that a shockwave caused within the system, is being amplified there.
     
  7. Cobra1365

    Cobra1365 Member

    Joined:
    Feb 7, 2011
    Location:
    Delaware
    That’s what it appears to be. So, then, is it better to put the arrestors closer to the far end or where the flow begins? I’m thinking either way, it’s a trip into my crawl space...just whether I want to crawl all the way to the end and install them in the distro lines just before they turn upwards to the bathrooms. Or, is it best to put one at each of the toilets and the washer?
     
  8. Bannerman

    Bannerman Well-Known Member

    Joined:
    Mar 19, 2014
    Location:
    Ontario, Canada
    An arrestor will be usually most effective where the shockwave is produced. For example, water flowing through a washing machine solenoid valve that is suddenly closed, may be considered similar to the energy of a vehicle slamming into a large tree. The kinetic energy must be suddenly dissipated so placing a shock arrestor at the shock source will absorb most of that energy as opposed to 100% being transferred and reflected back through the entire plumbing system.

    Your pressure tank will already act as a super sized arrestor at the source of flow.

    As you said "Lately, we’ve noticed a thunk in the far end of the house ...", it then sounds if the water hammer issue recently commenced and did not occur directly upon installing the new pump system. Suggest bypassing or removing the 10-micron and carbon cartridges from their filter housings to determine if there is any change to the hammer issue. You might also bypass the Acid Neutralizer to determine if there will be any difference. When there has been a change to cause a symptom without an obvious reason, it will generally take some investigation which may involve elimination to determine the actual source of the issue.
     
    Last edited: Jan 9, 2021
  9. Cobra1365

    Cobra1365 Member

    Joined:
    Feb 7, 2011
    Location:
    Delaware
    Great info! Thanks!
     
  10. Cobra1365

    Cobra1365 Member

    Joined:
    Feb 7, 2011
    Location:
    Delaware
    So, I bypassed the filter system and still have the issue.

    I’m thinking I’ll add two arrestors at the washer and two more at the toilets (opposite ends of the house). The next question is will those two on the toilets dampen the bang when the adjacent sinks are shut off?
     
  11. Bannerman

    Bannerman Well-Known Member

    Joined:
    Mar 19, 2014
    Location:
    Ontario, Canada
    Items that suddenly stop water flow such as solenoid valves used in a clothes or dish washers and some toilet fill valves, are usually the cause of most hammer issues as they are either fully ON or fully OFF with nothing in between. Sink & bath faucets will not usually cause hammer issues are they are typically turned off relatively slowly with no immediate change from full ON to full OFF.

    If you are experiencing hammer when any water flow is stopped, suggest performing a full inspection of your plumbing system to look for loose or unfastened pipes that move and may knock against other pipes. wall studs or floor joists when there is a flow change through that section of pipe.
     
    Last edited: Jan 14, 2021
  12. Cobra1365

    Cobra1365 Member

    Joined:
    Feb 7, 2011
    Location:
    Delaware
    Yes, I plan on climbing under the house and checking the bladder tank as well as the piping.

    The sink faucets are lever type that turn off within a quarter turn. So, relative quick to shut off.
     
  13. Groovy8

    Groovy8 New Member

    Joined:
    Jan 26, 2021
    Location:
    NorCal
    Please post an update here with your findings.
    I have a very similar problem. Thumping sound after turning off the sink or when the toilets stop filling.
    We recently had a plumbing reroute due to a slab leak and the plumber assures me that all pipes are secured properly, otherwise they wouldn't have passed the inspection. The plumber suggests replacing shower pressure balancing unit in one of the bathrooms as well as the comfort valve for the Grundfos hot water pump, because when he shut those off, the thumping noise was gone.
     
  14. Groovy8

    Groovy8 New Member

    Joined:
    Jan 26, 2021
    Location:
    NorCal
    Update from my side.

    I disconnected the mixer comfort valve for Grundfos hot water pump and the noise went away, connected it back and it started happening again with that specific sink.

    For the toilet, I installed an arrestor, and it made the noise less obvious. I think I'm just going to live with it.
     
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