32mm Waste Pipe in Metal Frame wall

[MortarThePoint]

What height should my waste pipe go into the stud wall?

 

Exciting times getting the partitions up and starts to feel like a home. I want to route the waste pipe of a basin through the wall to have a clean finish in the bathroom. There's only one place I have to do this, others are on blockwork walls or behind cabinets. The wall is 70mm C-studs (BG) and I plan to use 32mm ABS solvent weld pipe.

 

The main question I have is what height the pipe should penetrate the wall for attachment to the basin. The basin will be a free standing one (wooden unit with basin on top). We haven't chosen this item yet and it may be one I make myself, but it would be nice to have the pipe at a sensible height that allows options. I'll probably fit a pattress to allow the future option of hanging a basin on the wall, but haven't decided yet. The cut-outs of the studs are around 500mm off the bottom, though I think I can flip them over and make it more like 300mm.  Should I do that and then have a vertical section on the right of the drawing as in the second image which allows easier future adjustment of the wall penetration?

 

At the end of the wall there will then be a vertical to get down to a trench in the screed. I hope this isn't noisy. At the moment the floor channel of the stud wall is screwed to a 4x2 which is continuous to the wall so I'll have to work out how to butcher that to make the trench go under the floor channel. If I can't do that, I'd have to box in the pipe at floor level which would be unfortunate, but not the end of the world. The trench is about 500mm long before a large hole in the floor that will be shared with a bath waste.

 

 

rodding access

 

[MortarThePoint]

Hmm, does this second drawing create an S-trap which is a no-no?

[Nickfromwales]

1 hour ago, MortarThePoint said:

Hmm, does this second drawing create an S-trap which is a no-no?

Err, nope! A trap is formed when the pipe rises again, after the basin has discharged, 'trapping' water eg blocking the pipe. Yours both show continuous falls so are fine, however option 1 would be the quietest method. You hear much more nose / sound from water changing direction and from significant drops before the invert.

FYI I have started wrapping soil and waste pipes with Kilmat / other sound deadening mat as a solution to banning the higher frequency noise, plus as much acoustic rockwool insulation as is practicable for the lower. It is imperative that the pipe runs do NOT contact the metal frame as that will be like an amplifier.

Edited May 2, 2022 by Nickfromwales

[MortarThePoint]

13 minutes ago, Nickfromwales said:

Err, nope! A trap is formed when the pipe rises again, after he basin has discharged, 'trapping' water eg blocking the pipe. Yours both show continuous falls so are fine, however option 1 would be the quietest method. You hear much more nose / sound from water changing direction and from significant drops before the invert.

FYI I have started wrapping soil and waste pipes with Kilmat / other sound deadening mat as a solution to banning the higher frequency noise, plus as much acoustic rockwool insulation as is practicable for the lower. It is imperative that the pipe runs do NOT contact the metal frame as that will be like an amplifier.

 

The basin would have a U-trap before the wall penetration so combined with the 90degree in the wall that would make an S-trap. That's bad for symphonic emptying isn't it?

 

What are you thoughts on height?

[Nickfromwales]

1 hour ago, MortarThePoint said:

so combined with the 90degree in the wall that would make an S-trap

No, it wouldn't. A trap does what it says, traps water. Zero water will remain in the above images, and the only 'trap' will be whichever you decide to go under the sink ( S / P / Bottle etc ).

1 hour ago, MortarThePoint said:

What are you thoughts on height?

I'll never get tired of 6' blondes  

 

Basins are typically ~820-830 from FFL so that's the height of discharging pipework. Some go horizontally to a soil stack, others outdoors to a snow box, some under DPM level to a drain gulley and so on. What happens after your "90o bend"? 

[MortarThePoint]

20 minutes ago, Nickfromwales said:

No, it wouldn't. A trap does what it says, traps water. Zero water will remain in the above images, and the only 'trap' will be whichever you decide to go under the sink ( S / P / Bottle etc ).

I'll never get tired of 6' blondes  

 

Basins are typically ~820-830 from FFL so that's the height of discharging pipework. Some go horizontally to a soil stack, others outdoors to a snow box, some under DPM level to a drain gulley and so on. What happens after your "90o bend"? 

 

The pipe goes about 500mm along the floor, joins the bath waste and goes 200mm down through floor before going 1800mm along ceiling void and joining soil stack. I may not pass through floor though and join stack above floor, but that area will be very busy.

 

So I can't going purely horizontally to the stack unless I penetrate the wall at skirting board level which would be strange.

[Nickfromwales]

18 minutes ago, MortarThePoint said:

So I can't going purely horizontally to the stack unless I penetrate the wall at skirting board level which would be strange.

No need to. Done plenty as you indicate, more than I can count.

18 minutes ago, MortarThePoint said:

The pipe goes about 500mm along the floor, joins the bath waste and goes 200mm down through floor before going 1800mm along ceiling void and joining soil stack. I may not pass through floor though and join stack above floor, but that area will be very busy.

That's fine. You need to use 50mm waste pipe for everything from stack to bath, and then 50mm from bath to the rising bend at the image above. Reduced on the vertical output of that bend ( not elbow ) with a 50x32mm reducer. You will deffo need to fit either a 50mm AAV under the bath ( if you've got a removable bath panel ), or take the 32mm waste pipe up from the 50mmx32mm bend to a 32mm AAV to an above attic / eave space(?), or at the very minimum put anti-vacuum tras on both basins in both rooms meeting that run of 50mm pipe.

[MortarThePoint]

6 minutes ago, Nickfromwales said:

No need to. Done plenty as you indicate, more than I can count.

That's fine. You need to use 50mm waste pipe for everything from stack to bath, and then 50mm from bath to the rising bend at the image above. Reduced on the vertical output of that bend ( not elbow ) with a 50x32mm reducer. You will deffo need to fit either a 50mm AAV under the bath ( if you've got a removable bath panel ), or take the 32mm waste pipe up from the 50mmx32mm bend to a 32mm AAV to an above attic / eave space(?), or at the very minimum put anti-vacuum tras on both basins in both rooms meeting that run of 50mm pipe.

 

Thanks Nick. The bath is freestanding so it would be a pain to have an AAV there. Could the AAV be in the stud wall with some form of air access to the stud wall? Another option that might be possible is to keep the bath and basin wastes separate all the way to the stack.

 

This is what I was worrying about in terms of an S-trap:

Though it would be more like this I guess:

 

Could I solve it all by having the AAV off that initial in wall elbow? If just having the AAV in the wall, I would make sure it is well above the top of the basin.

 

[MortarThePoint]

The AAV could be above the sink and behind the mirror. To service the AAV, I could remove the mirror and an access panel. I suppose it raises the question of how does air enter the wall and does it bring moisture in with it?

 

I know there are small trap based AAVs but suspect they wouldn't admit enough air to prevent the problem in this situation.

 

9l/s for 1¼" solvent weld pipe

https://mcalpineplumbing.com/air-admittance-valves/ventapipe/vpsf-4050-ventapipe-4050

[Nickfromwales]

No need to go crazy. Assuming you have a 110m AAV or an SVP for the rising foul stack, the 2 anti-vac basin traps will be all you need here. The horizontal breaks in the run, coupled with the 50mm pipe, will be all the air break you'll need.

 

Trust me, I'm a pipe doctor  

Edited May 2, 2022 by Nickfromwales

[MortarThePoint]

On 02/05/2022 at 11:53, Nickfromwales said:

FYI I have started wrapping soil and waste pipes with Kilmat / other sound deadening mat as a solution to banning the higher frequency noise, plus as much acoustic rockwool insulation as is practicable for the lower. It is imperative that the pipe runs do NOT contact the metal frame as that will be like an amplifier.

 

So do you just have the Kilmat wrapped pipe resting on the studs or do you use pipe clips screwed to the OSB in the bathroom side of the wall to hold it in place?

[Nickfromwales]

2 hours ago, MortarThePoint said:

 

So do you just have the Kilmat wrapped pipe resting on the studs or do you use pipe clips screwed to the OSB in the bathroom side of the wall to hold it in place?

I suspend the pipe with black powder coated all-round patent band ( Link ), only fixing to the upper chord. 
 

This is to;

a) set the fall in the pipe

b) physically decouple to pipe from the ceiling below / lower chord. 

[MortarThePoint]

1 hour ago, Nickfromwales said:

I suspend the pipe with black powder coated all-round patent band ( Link ), only fixing to the upper chord. 

 

You link seemed to get broken. I guess this is the stuff you mean: https://www.amazon.co.uk/Galvanised-Steel-Fixing-Perforated-Builders/dp/B08M3L7YYZ/

Looks good with the PVC coating. I think this is one of those materials that once you start using it you discover lots of good uses for it. I've yet to use it but can already start to think of some other uses.

 

How do you use that within a stud wall like I am looking to do? Do you secure a loop of it to the metal stud and suspend the pipe in the cutouts?

[MortarThePoint]

@Nickfromwales this is what I've ended up with.

The cutouts are only slightly larger than the pipe so no real way to isolate. I've used rubber edge strip which will hopefully help. I'll be putting some Kilmat on the pipe and filling wall with Acoustic Partition Roll.

[Conor]

You could do with a couple pipe clips screwed to the OSB.

[MortarThePoint]

12 minutes ago, Conor said:

You could do with a couple pipe clips screwed to the OSB.

Thanks, I had wondered about that. It's very snug where it passed through the studs (in fact concerned it may squeak due to thermal expansion) but clips would be good I agree.

[Nickfromwales]

16 hours ago, MortarThePoint said:

Thanks, I had wondered about that. It's very snug where it passed through the studs (in fact concerned it may squeak due to thermal expansion) but clips would be good I agree.

Just a small squirt of exp foam in the gap under the pipe as it passes through the stud would be fine. If you clip then you reconnect the pipe to the OSB which will be like an amplifier. 
Better off using all round patent band as a sling and screwing it top dead center into the metal frame if a mechanical fix is what’s preferred. 
Personally, I’d just foam and call it a day. 

Edited May 30, 2022 by Nickfromwales

[Onoff]

You could 3D print grommets to go round the pipe. Either flexible or in two halves. Complete overkill of course.

 

...or you could foam it.

 

I know which one I'd choose 😂

[Nickfromwales]

5 hours ago, Onoff said:

You could 3D print grommets to go round the pipe. Either flexible or in two halves. Complete overkill of course.

 

...or you could foam it.

 

I know which one I'd choose 😂

Yes, so do we. FFFS ( first F is for Foam  ). 

[MortarThePoint]

On 30/05/2022 at 06:59, Nickfromwales said:

Just a small squirt of exp foam in the gap under the pipe as it passes through the stud would be fine. If you clip then you reconnect the pipe to the OSB which will be like an amplifier. 
Better off using all round patent band as a sling and screwing it top dead center into the metal frame if a mechanical fix is what’s preferred. 
Personally, I’d just foam and call it a day. 

 

How about a 50mm pipe clip having padded the pipe with UFH perimeter insulation or some other padded tape.

I'm avoiding using spray foam in the airtightness envelope (I know, it's a pain).

[Russell griffiths]

@MortarThePoint why are you avoiding using expanding foam ??

i use it absolutely everywhere. 

[MortarThePoint]

6 minutes ago, Russell griffiths said:

@MortarThePoint why are you avoiding using expanding foam ??

i use it absolutely everywhere. 

 

I know, it's a staple of modern building. It's to do with indoor air quality and VOCs. I don't think it's really an issue but we've started down that road now so need to see it through

[saveasteading]

16 minutes ago, Russell griffiths said:

why are you avoiding using expanding foam ??

i use it absolutely everywhere. 

I hate it. It gets used to overcome all sorts of issues that have better solutions.

It has cost me thousands, when it leaks over metal cladding, doesn't come off again and needs a whole wall replacing. Mt nobody did it but my cleient didnt care who did it.

It fills voids with potential damage through damp.

It probably shrinks over time.

It drips and sticks.

 

So even for my own job with my own control, I would find another way. Probably stuffing the gap with surplus foam packaging, which will be  a more reliable and flexible solution.  And can be removed if necessary.

[Pocster]

31 minutes ago, Russell griffiths said:

@MortarThePoint why are you avoiding using expanding foam ??

i use it absolutely everywhere. 

Expanding foam is my go to for f ups or indeed “ quality workmanship “

[saveasteading]

2 hours ago, pocster said:

Expanding foam is my go to for f ups

Maybe it was you that cost me all that money!