Soundproofing soilpipe with expanding foam

Use rockwool wrapped around the pipe - then box in and cover with 2 layers of half inch plasterboard.

 

As Hallbeck said, use rockwool or any loft insulation, pack it in nice and tight.
If you start squirting foam in there, apart from using loads of it, you will never get it out again if you need access to pipe.

 

use roof insulation if you use expanding foam pipe will never come out in case of leaks

 

Only an idiot would insulate a soil pipe with exp foam.....apart from the high cost and huge difficulty in future maintenence the resulting expansion will probably 'pop' the boxing off the walls!

Use rockwool as advised.

 

Soapy, use expanding foam. And then come back on here and tell us how it went.

Lawd knows this forum needs more humour...


Ok, you wanna proceed? Is the pipe boxed in on three sides with only the front to be replaced? Good. Ok, get yer foam gun and point the nozzle in at an angle so's it aims directly behind the pipe - I'm guessing there's at least an inch gap behind there? Ok, start at one end and sqeeze gently whilst moving the nozzle upwards (or downwards...) to leave a 1-2" bead in its wake. Give this a few minutes to see how far it expands. Then just keep adding long lines of foam all the way around, allowing expansion time between each. As said above, it's powerful stuff and could likely bow out the side of your boxing. At the front, it doesn;t matter too much if it expands over the line - just let it soldify fully and use a saw to cut down flush with the framework. Then add the lid.

And pray the pipe doesn't leak or need modifying.

And leave your address so that no-one on here buys your house.

How much do you need? Dunno - I'd buy just one of these large cannisters first and see how it goes. Remember - allow expansion time...

 

Hi, let me start by saying, "I was that man". I used expanding foam from a number of cans to soundproof a noisy soil pipe which passed through my dining room. In my defence it did state on the can that the product could be used for sound insulation.

Anyway, I squirted the foam into a series of holes I'd drilled into the plasterboard boxing which surrounded the pipe. I used inspection holes I'd also drilled to check the foam was expanding into all of the void between pipe and plasterboard. Long story short, the foam made matters much, much worse. You could heard every water droplet move with crystal clarity. At first I hoped the wife wouldn't notice but no go, so I had to demolish the plasterboard boxing and spend a very cross day removing the foam - if you ever have to do this a bread knife works well by the way.

So I did a bit of research; it comes down to this: the foam actually bonds the the pipe to the plasterboard providing an acoustic path for sound transfer. Not good!

Sound waves propagate either through the building structure mechanically, or through an air path. Sound in air can either be absorbed, or reflected at an interface between a light material and a heavy one. I used soundservice.co.uk and bought the proper fireproof stuff, some self adhesive acoustic foam to wrap around the pipe, sound absorbing mineral wool and a heavy lead like material. I carefully wrapped the pipe in the sticky foam making sure there were no air gaps (sound absorption) and using gaffer tape as required. I used evostik to glue a layer of the flexible lead like material on top (sound reflecting interface). Then I rebuilt the plasterboard boxing and pushed the mineral wool (more sound absorption) into the remaining void - don't pack it too tight by the way. Last top tip; I attached the the plasterboard to my solid wall using screws in such a way as to trap some foam rubber in the gap to decouple the structure.

Result? Well, it's whisper quiet now, wife happy. It was a bit expensive (£80) and a big faff but definitely worth it.

 

Changing your diet may help!