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Where do you put a water hammer arrestor

StephenNJ's picture

My washing machine causes a water hammer banging.  My kitchen faucet does it sometimes, but not always.  I purchased two Watts water hammer arrestors that go in the water line.  See picture below.  I plan to put one of them on both the hot and cold feed lines.


My question is:  Should I put the arrestors as close as possible to the washer, or put then further upstream so that I stop the water hammer from the kitchen sink as well (that would be about 20 feet away from the washer feed).


My unprofessional opinion is that the closer to the washer the better.


(post #73420, reply #1 of 12)

At the source of the hammer is best. ie. right at the washer valve. Then add a second set of arrestors for the kitchen. 

(post #73420, reply #2 of 12)

near to the end of the line as practicle...


really long runs get an intermediate...


 


 


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(post #73420, reply #3 of 12)

Note that sometimes "hammer" is simply due to not having the pipes properly anchored.


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Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #73420, reply #4 of 12)

DanH is right. The pipes are loose and not secure. Whether in the attic or under the floor, just grab the pipe and shake it, you will create that banging noise. Solution is to wrap it with carpet padding or something durable/soft and clamp it down. Also stuff padding on the tight side of the stud hole to keep the pipe from touching wood.
Plumbers who don't properly secure and isolate pipes were not taught correctly. Plumbing Inspectors should not allow water pipes to just lay on top of ceiling joist. Qualified plumbers are getting harder to find.

(post #73420, reply #5 of 12)

If the pipes run parallel to the joists you can use plastic pipe hangers that hold the pipe out away from the joists. I used them for the new plumbing in my bathroom addition and they are great. I don't have any water hammer problems and they greatly reduce the sound of water rushing through the pipes.  They are available at most hardware and home improvement stores.

(post #73420, reply #6 of 12)

You might already have them inside the walls on the supply lines. Over time they get waterlogged and fill up with water, and since all the air is gone, bang.


Try draining your whole house.  Turn off the water main supply.  Open the hose spigots, or anything lower if you have it, like a sink in the basement.  Then open up all your fixtures and let the water drain out.  Then close them up, turn the water back on, bleed the fixtures, and it might help.


I noticed banging in some of my pipes that never banged before.  When the city was here to replace a water meter, I just did it then.  No more banging.


Pete Duffy, Handyman

Pete Duffy, Handyman

(post #73420, reply #9 of 12)

You get more of that on the older "air riser" than you do with a diaphram/bladder hammer arrestor.


28 days is all it takes too have the water absorb the air in a capped riser.


We rarely ever put the riser style in anymore cause the inspectors make us put in a bleeder valve & access door.


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(post #73420, reply #10 of 12)

The dry riser thing is highly variable.  I've seen them keep working for years sometimes. Or, it might only be a few weeks.  The empty and refill trick is so easy, it's worth a try.  Of course, dry risers are an old fashioned idea, so there might not even be any in recent houses.


As for a bleeder valve to re-fill the risers, if your water pressure is 60 psi, the air in the riser will have only about 1/5 the volume it did at atmospheric pressure.  So, its possible to get a lot less air that way than with a complete refill.



 


-- J.S.


 


Edited 8/18/2006 6:37 pm ET by JohnSprung

 

 

-- J.S.

 

(post #73420, reply #11 of 12)

None in our house -- 1976 construction.


If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #73420, reply #12 of 12)

I put some in about 1978-9.  It was considered old fashioned at that time. 

 


 


-- J.S.


 

 

 

-- J.S.

 

(post #73420, reply #7 of 12)

There is a hammer arrestor that connects right at the washer valves, screws right in then the washer hose screws into them.  Of course I found them after I installed an arrestor at the main line coming into my house.  I think it was an oatey but i may be wrong.   I'm sure you can google and find one quick.


Have a good day


Cliffy

(post #73420, reply #8 of 12)

I second what cliffy said.  I found some in a big box store around 5 years ago.


That's probably enough.  You can add another near the kitchen later, but I don't think you'll need to.