Reducing noise from soil pipe

[CC45]

Hi all,

 

Today I got the bath plumbed in - all good except when I let the water out, no leaks but the water makes a fair bit of noise when it drops down the 110mm pipe to the ground floor.  The worst of it is where it just goes below the ground floor, the shallow bend in the pipe aint very far below floor level & its when the water hits it there that really generates some noise.  I have enclose the pipe in RWA45 acoustic slabs & its boxed in using 15mm PB but its pretty noisy through the 6"x6" inspection / rodding hatch. I will add another layer of 15mm PB but was thinking about whether some sound deadening foam sheets would also help - has anyone used them?  Any thoughts?  My idea was to wrap it around the 110mm pipe as well as put some on the inside of the hatch.  Any other suggestions?

 

Cheers

 

https://www.amazon.co.uk/Sound-insulation-Damping-deadening-Alubutyl/dp/B005JRZPMM/ref=asc_df_B005JRZPMM/?tag=googshopuk-21&linkCode=df0&hvadid=309952060520&hvpos=1o5&hvnetw=g&hvrand=13959877016630121023&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9045438&hvtargid=pla-429189207337&psc=1

Edited April 8, 2019 by CC45
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[Onoff]

I encased my horizontal 110mm soil pipe in spray foam within the base of the stud wall. Aqua Panel over that then tiles. I was advised here that Rockwool slabs might have been better. 

 

End result is more than I could have hoped for, it's silent. Loudest bit is the flushing in the pan. Refill is near silent helped I'm sure by the ex studio acoustic foam tiles I lined where the Geberit frame sits.

Edited April 8, 2019 by Onoff

[Moonshine]

Typically you would use a mass loaded vinyl with a decoupling layer to separate the pipe to the vinyl, an off the shelf product to do this is Soundlag or similar, with the mass of the vinyl going up to 8 kg/m².

 

In your case you have wrapped the pipe on mineral wool already, that is o.k for the decoupling layer, and also absorption once the mass layer is wrapped around, but won't be effective without the secondary mass layer.

 

I recommend that you loosely wrap the lagged pipes with a mass loaded vinyl of circa 8 kg/m², overlapping and taping the joins, fitting the vinyl around the mineral wool without compressing it too much.

 

Obs, this is advice based on not seeing the area you have got to work with.

[TheMitchells]

we filled loose rockwool into the boxed area, around the pipes and double plasterboarded with usual pb and that seemed to work well.

[CC45]

Having spent a few hours on this today, I'm not convinced there is an easy solution.  The problem is the initial bend is only just below the surface of the floor and when the water hits this it generates the noise.  I've added another layer of PB - reduced but not by a lot.  I suspect I need to dig a small area of the floor up and try and drop this bend to below the floor - possible to do but a real pain.  This may be a case of getting my big boy pants on and just doing it.

 

Thanks for the advice - if I do drop the height then I will look to add these on subsequently.

[ProDave]

Is this bottom bend a proper rest bend or an ordinary tight bend?

[CC45]

Underneath the floor its a proper rest bend but above this there are two 45deg bends to bring the soil pipe up close to a corner - this is the problem since these bends are above the B&B floor and its not far for the sound to transmit through.  Going to very gently dig up the floor (got ufh pipes in that area) - its not a big area (prob 8" x 10") - hopefully I won't damage a pipe & if one is in the way I can ease it to one side.  Worst case scenario is I will have to put a joint in. Hopefully it will all be OK.  Lesson learnt.  Experience gained.

[Carrerahill]

May be an option to try the Marley Dblue acoustic pipe - if it is all installed and you are happy with it then probably not an option but might be.

 

What are your floors made of? If concrete you could pour concrete in around it. Cast Iron pipes never made much noise because they were solid and would not vibrate or carry sound - adding concrete would have a similar effect - probably against reg's... but... 

 

https://www.marleyplumbinganddrainage.com/products/soil-systems/dblue/

 

 

Edited April 10, 2019 by Carrerahill

[ProDave]

54 minutes ago, CC45 said:

Underneath the floor its a proper rest bend but above this there are two 45deg bends to bring the soil pipe up close to a corner - this is the problem since these bends are above the B&B floor and its not far for the sound to transmit through.  Going to very gently dig up the floor (got ufh pipes in that area) - its not a big area (prob 8" x 10") - hopefully I won't damage a pipe & if one is in the way I can ease it to one side.  Worst case scenario is I will have to put a joint in. Hopefully it will all be OK.  Lesson learnt.  Experience gained.

Can you use say two 15 degree bends and make the offset over a longer distance, but with less "obstruction" to flow?

[CC45]

Not sure - I will check it out tomorrow - it would certainly reduce the noise especially if the 1st one was 15deg........

 

Would rather not spend a day carefully digging up the floor!

[Onoff]

Can you introduce new fittings easily enough? Slip couplings can help.

[CC45]

Had a good look at this today - to get rid of all the bends and have a straight fall will require ~ 6" x 8" of floor dug up - pain but not OTT.  The boxing in will obviously be bigger.  Planned to give this a bash on the weekend.  Hopefully no ufh pipes where I need to dig.