Quieting a noisy soil stack

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Charlie_Powell

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Hi all,
I have a three-level, end of terrace house. It has an internal soil stack (black PVC), and it can be noisy. When people on higher levels flush, it is very audible in the sitting room. The stack doesn't pass through the sitting room. It passes through a small groundfloor WC surrounded by drywall, but the sound still escapes into the sitting room and hall. The first floor is a hollowcore slab and this might have implications for alterations. So I am looking at ways to quieten the system. I could open up the boxed in soil stack in the bathroom and surround the pipe with pipe insulation. I was told this could reduce the sound by about 10 decibels (equivalent to 50% reduction). I wonder would it be a better investment to just cut out this section of the soil stack from the ground level to the hollowcore slab and replace with an acoustic soil stack pipe that doesnt leak noise and restore the drywall. I wonder would people here have any thoughts and suggestions?
 
Charlie_Powell said:
I could open up the boxed in soil stack in the bathroom
Click to expand...

I would try this and fill the boxing in with acoustic fibreglass insulation. Also check the soil pipe isn't touching any part of the boxing in, walls, or ceiling which can make any noise travel easier.
 
Charlie_Powell said:
replace with an acoustic soil stack pipe
Click to expand...
Acoustic soil pipe doesn't absorb sound and stop it from 'leaking'.

Acoustic soil pipe has an ultra smooth internal surface so when water runs over it on a horizontal run, it minimises the creation of turbulence (noise).
On a vertical drop you will always have turbulent water that is inherently noisy, therefore the best solution is pack the void between the pipe and box section with sound absorbing material.
 
Madrab said:
Acoustic soil pipe doesn't absorb sound and stop it from 'leaking'.

Acoustic soil pipe has an ultra smooth internal surface so when water runs over it on a horizontal run, it minimises the creation of turbulence (noise).
On a vertical drop you will always have turbulent water that is inherently noisy, therefore the best solution is pack the void between the pipe and box section with sound absorbing material.
Click to expand...
What about those old style cast iron pipes. Seem to be very much confined to old buildings in the UK but I heard of Americans using them in new builds for quietness
 
With cast, it's a much thicker wall and heavier/more dense construction, so it doesn't resonate the same way plastic does.

That being said, it still isn't totally silent either, more so the older it gets as it delaminates slowly inside and gets more turbulent.
 
Cheers lads. I will aim then to open up, wrap with acoustic pipe insulation, use the oppertunity to install unrelated cabling behind and then packe in dense rockwoolslab in the remaining space.
 
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