Where to install hammer arrestor

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Blake101, Oct 18, 2016.

  1. Blake101

    Blake101 New Member

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    After living in our new house a few months we noticed the pipes were making noise above and near the kitchen when the dishwasher was running. The plumbing is the yellow cpvc and runs through the attic. Should I install the arrestor up there or on the pipe under the sink feeding the dishwasher? Also, which kind should I buy, there are many types at HD?
     
  2. Reach4

    Reach4 Well-Known Member

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    A water hammer arrestor needs to be very close to the valve that is closing.

    Water hammer is a bang that happens when a valve closes fast. Chattering or machine gunning is a different thing, and that might indicate insufficient pipe clamping.
     
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  4. Blake101

    Blake101 New Member

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    When I can hear the valve coming on/off I notice a noise but it also seems like the whole time it is open then the pipe is making a tapping noise periodically but not too fast. I think I'll try the hammer arrestor under the sink first and then go in the attic and add some clamps if I can fit back in that area.
     
  5. Terry

    Terry Administrator Staff Member

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    I normally put the hammer arrestor at the shutoff for the dishwasher.
    Putting it on the hot side to the kitchen sink would be close enough too. They also go on the icemaker line and the washer lines.

    Make sure your shutoff is open all the way too. On a multi-turn, I open all the way and then back in just a bit. That keeps the seal under the packing nut in better shape, and it's easier for the next person to determine which way the valve goes. I've seen people twist with all their might the wrong direction before realizing what they have done.
     
  6. Blake101

    Blake101 New Member

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    Thanks for the reply Terry. That is a good idea, I've noticed the same thing with the washer as well. It wasn't so bad until we stopped running our A/C fan at night. I noticed when the fan would run at night we would get really high humidity and now that we stopped I can hear every little noise at night and it's been keeping me up.
     
  7. AlGreen

    AlGreen Member

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    A few years back I installed a hammer arrestor at the water shutoff for my dishwasher, and I still had hammer. I've lived with it for a while now, but I really should revisit and try to correct the issue. The only other thing I can think to do is try and fit another mini job immediately before the valve under the dishwasher. Thoughts?


    20200705_203012.jpg
     
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Think of the water as a piston that, once moving, wants to keep moving. It will bounce against whatever tries to stop it. That's the quick-acting valve, so having somewhere for it to go, as close as possible to that valve generally helps the most.

    It was mentioned hearing ticking sounds...that's likely from the plastic pipes expanding while hot water is running caused by a too tight clamp or hole and the pipe jumps a bit as it catches, then slips trying to relieve the pressure/tension on the piping. Any restriction must allow it to move as needed without much friction to stop it.
     
  9. Jeff H Young

    Jeff H Young In the Trades

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    Same things I do with arrestors and the multi turn stop. A basic place I start with water hammer problems is a pressure check
     
  10. AlGreen

    AlGreen Member

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    The water pressure in my house is pretty consistently 60 PSI (just double checked it).
     
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  11. Jeff H Young

    Jeff H Young In the Trades

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    So it is clear, while hot water is running you hear a sort of ticking? or more of a pounding as it turns off or on? Water hammer arester wont help the former. A well installed system with a little luck you dont even need arrestors though code calls for them on quick acting solenoid valves. If its the ticking from expansion not a lot you can do other than open walls and rework strapping. If you already have an aresstor and add another it cant hurt but my experiance is if you have a hammer and add an arestor it dosent help adding asecond arrestor. I might add one but wouldnt have high expectations
     
    Last edited: Jul 6, 2020
  12. AlGreen

    AlGreen Member

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    Jeff Young, I think you may have mixed me up with the OP, who started this thread back in 2016.

    To recap, in my situation (few posts above), given that I've tried installing an arrester at the shut-off for the dishwasher and the house pressure is at a reasonable 60 psi, I'm thinking my only option at this point is to try and fit an arrester immediately after the dishwasher inlet valve. Unfortunately, it's pretty tight in there, even for a mini.


    20200715_174852.jpg
     
  13. Jeff H Young

    Jeff H Young In the Trades

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    I wouldnt expect that to help but sometimes you gotta try something. is there a chance the copper line has a kink in it? that can cause a hammer
     
  14. WorthFlorida

    WorthFlorida The wife is still training me.

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    To be sure this is a hammer effect, as you hear it open the sink faucet hot water side. If it is a hammer affect the water will start to pulse slightly and eventually go away. I think, as it was said above, the hot water pipe is expanding and moving where it rubs against perhaps a wood joist or floor sheeting. Do not run the dishwasher but just run the hot water at the sink slow enough that it does make much noise and then listen for it.

    I grew up in a home built in 1953 and all copper pipes. The heating system was a hydronic hot water system with radiators in every room. I recall many nights when the heat turned on hearing the clicking noise as the pipes and radiators expanded. I could tell how cold it was outside by how long the clicking lasted as heating system ran.
    Here is the funny part. My father died in Aug and the daytime caretakers started to live (24/7)at the home to care of mom. When the heating season started, one of the caretakers swore that she would hear my father walking in the house (creaky floors) during the night. I new it was the heating system doing it.
     
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  15. AlGreen

    AlGreen Member

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    I didn't see any kinks in the line when I last looked, but I'll check again.

    @WorthFlorida Thanks. It's definitely water hammer. I'm not hearing the tapping noise that Blake101 was talking about in his original posts for this thread. In my case, when the dishwasher valve shuts, the pipes bang immediately after.
     
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  16. Reach4

    Reach4 Well-Known Member

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    I don't know how you would test a water hammer arrester. Do they fail? I don't know, but what device with a hidden moving part doesn't fail?
     
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  17. Jeff H Young

    Jeff H Young In the Trades

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    Ive had a heck of a time quieting water hammers. One that stands out in my mind was a New house we plumbed had called us back several times for a water hammer. We installed several water hammer arrestors even opened walls in several places only change was you could hear the arrestor squeak . There was a crew of us maybe 4 guys, I came up with a conclusion that something was lodged or a kink in soft copper under ground.
    Talking with our superintendant we decided to run a 3/4 inch copper line in attic to a main in garage and feed that area with the additional line. it solved our problem removed all the watter hammer arestors patched and painted the walls.
    This was my worst kinda got lucky never knew exactly what went wrong
     
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  18. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Hammer arrestors come in two styles:
    - a piston that slides back and forth with an air chamber on one side
    - a bladder, similar to an ET, but lots smaller..

    Any of them can eventually fail, either the seal that traps the air or the bladder tearing and filling up with water.
     
  19. AlGreen

    AlGreen Member

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    The arrestor mounted under the sink (first pic) didn't stop the dishwasher water hammer when it was brand new. So unfortunately, a worn out arrestor isn't the problem.

    FWIW I found that my washing machine arrestors weren't very effective when I first mounted them at the supply shut-offs. Then I moved them to the back of the washer (immediately after the valves and before the hoses), and the water hammer was solved. That's why I'm thinking that I need to install one right after the dishwasher valve.
     
  20. Jeff H Young

    Jeff H Young In the Trades

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    Try doing that Al Green. sometimes you gotta try differant things. A well plumbed and strapped house dosent usually get water hammer Sometimes I dont install them if its not new construction or inspected they are pretty easy to add. and I think an icemaker is over kill but thats the law. My experiance is a real bad water hammer dosent get solved with an arrestor. there is a reason for water hammer. its not caused by lack of an arrestor at least not very often
     
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