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Discussion Starter #1 (Edited)
A quick tale of my fight against pipe noise...

I am building a HT in the basement of a new house. One of my primary noise concerns is from a drainage stack which enters the basement and turns horizontal overhead just behind the main listening position. The pipe is PVC which most of you know it can be quite noisy. In this case it is ridiculously loud when someone flushes the toilet on the second floor and is something I knew had to be addressed before drywall goes up.

After considering several options, I happened upon a suggestion somewhere (may have been this forum, actually) to wrap the pipe in heavy carpet pad. The local home improvement store only sells this by the roll ($170) though I only need a few square feet. A friend in the flooring business was kind enough to give me some scraps of 1/2" thick, 8lb pad. I wrapped the offending section of pipe (drop from vertical stack, elbow, and a few feet of horizontal run) in 3 separate layers of pad, being careful to stagger all seams. When I was done, my wife was kind enough to flush the toilet a few times so I could hear the result.

To my astonishment, from floor level (standing on floor directly below the pipe) I could not hear the water hitting the bottom of the stack at all and could only hear a quiet trickle on the horizontal line downstream of the point where the wrap terminates. I figured it would help a little, maybe a lot if I was lucky, but it really killed the noise altogether. Best of all, it only took 10 minutes (not including the trip to pick up the scraps) and about 50 cents worth of duct tape.

Regards,
sga2
 

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Thats great that it worked, when i first started reading i was thinking you were gonna ask for suggestions so i was thinking of useing Dynamat or some other automotive type sound deadener but that stuff can be quite expensive and i think you came out on top by along shot, that awesome!:T
 

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Discussion Starter #5
Me too.

I was wondering if it can be enclosed in a box similar to those used for AC ducts :huh:
If you mean to use this as acoustical liner for a supply/return/transfer duct (e.g., in a dead vent system), I'm afraid that wouldn't meet Code since it is not plenum rated. What do you have in mind?

Regards,
sga2
 

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Pipe wrap is designed for this specific purpose. Adds mass and damps in one shot.
 

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Discussion Starter #7
Pipe wrap is designed for this specific purpose. Adds mass and damps in one shot.
True... However, mass loaded pipe lagging is neither inexpensinve nor available at most retailers (I don't know of any myself). And I figure many people that are finishing out a basement HT project might have some left over carpet pad anyway (if they are carpeting the room). If the scraps can be put to good use deadening some noisy pipes, why spend additional funds on a specialty product?

Regards,
sga2
 

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...one more thing... I used this to also reduce any vibration from the PVC that was leaning against the interior walls... cheap form of insurance against vibrations...
 

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I know it is 2 weeks later but I hope you don't mind if I jump in with a couple of additional suggestions. Ensure there is no rigid contact between the pipe and building at all - this includes replacing rigid pipe hangers or pipe clamps and also means cutting a 15mm clearance gap around the pipe where it penetrates the floor (assuming the floor is timber ...). The gap then gets caulked with a soft flexible sealant. Oversize pipe clamps can be used around the carpet pad or around a 12-20mm thick Armaflex foam-rubber sleeve.
 
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