AAV Location help

[Adam Harrington]

Hi, I have extended on the side of my house where the original soil stack was so now it is incorporated into the downstairs utility.
I’ve put a small en-suite above so I need to run the soil pipe up the wall, across the joists and up to the toilet. This will be boxed in
My problem is, there’s no option for the soil waste to vent outside so I need to put a aav somewhere.
Pictures show the position of soil pipe and the red Cross is the proposed toilet position. there’s a stud wall behind the toilet, would two 50mm wastes up to the loft be sufficient?
any other ideas?
thank you

[MikeSharp01]

would have thought that one 50mm AAV would be enough, its the vac cum you want to break after all. If you are working with building Control you could check with them what they deem acceptable.

[Conor]

Only needs to be above the highest trap, no need to put in the loft. We have ours on a branch in the airing cupboard behind the bathroom. Full 110mm one but our ES and kitchen both have 40mm ones in the cupboards below.

[Adam Harrington]

15 minutes ago, MikeSharp01 said:

would have thought that one 50mm AAV would be enough, its the vac cum you want to break after all. If you are working with building Control you could check with them what they deem acceptable.

I guess a 50mm one would be better than nothing right? 
So would you tee off the 110 with a t piece, and then convert to 50mm and send that up? 

[Kelvin]

Ours (110mm) is in the coomb wall adjacent to the en-suite and runs at an angle following the pitch of the roof. But we also have an SVP coming out the garage roof. 

Edited August 1 by Kelvin

[Adam Harrington]

15 minutes ago, Conor said:

Only needs to be above the highest trap, no need to put in the loft. We have ours on a branch in the airing cupboard behind the bathroom. Full 110mm one but our ES and kitchen both have 40mm ones in the cupboards below.

Ah okay, thank you. With it been a stud wall I thought to make it accessible in the loft if ever needs be. If I leave it just above the toilet it will be inside the stud wall. 

[Russell griffiths]

1 minute ago, Adam Harrington said:

Ah okay, thank you. With it been a stud wall I thought to make it accessible in the loft if ever needs be. If I leave it just above the toilet it will be inside the stud wall. 

It needs to be accessed for maintenance, they do fail. 

[Adam Harrington]

1 minute ago, Russell griffiths said:

It needs to be accessed for maintenance, they do fail. 

Thank you. Would you tee off the 110 and immediately change to 50mm? And then send the 50mm into the loft? 

[Adam Harrington]

Excuse my terrible scetch 😂 

toilet would be the end of the run, would it be ok to tee off further down the run, immediately change to 50mm and run the 50mm up inside the stud wall to the loft? 

[Marvin]

Hi @Adam Harrington

 

That is what I have done. better than boxing it in the room. works fine.

 

2 hours ago, Conor said:

Only needs to be above the highest trap, no need to put in the loft. We have ours on a branch in the airing cupboard behind the bathroom. Full 110mm one but our ES and kitchen both have 40mm ones in the cupboards below.

And this works well if, as @Conor says you make sure the AAV is above the top of the basin (if attached). 

 

Good luck

 

Marvin

[Adam Harrington]

31 minutes ago, Marvin said:

Hi @Adam Harrington

 

That is what I have done. better than boxing it in the room. works fine.

 

And this works well if, as @Conor says you make sure the AAV is above the top of the basin (if attached). 

 

Good luck

 

Marvin

Thank you for the help. 
I only have a 63mm stud wall to run it in, there’s a bedroom behind so no option to put it in a cupboard. 
if I was to put a 110 aav on the downstairs stack, and then a aav trap on the en suite basin. Is that enough or would it be pointless because of the 2 toilets upstairs?  

[Marvin]

21 minutes ago, Adam Harrington said:

Thank you for the help. 
I only have a 63mm stud wall to run it in, there’s a bedroom behind so no option to put it in a cupboard. 
if I was to put a 110 aav on the downstairs stack, and then a aav trap on the en suite basin. Is that enough or would it be pointless because of the 2 toilets upstairs?  

Think of the overflow risk. An AAV should be above the highest basin, shower tray or loo rim on the run in my opinion.

[Dan F]

We used a flexible 50 or 75mm pipe in one of the tricky locations where we needed to bring it up through stud-work into the loft, was easier that using rigid waste pipe.

[saveasteading]

4 hours ago, MikeSharp01 said:

working with building Control 

Does 50mm dia of air move as fast as 100mm dia of water? Fluid mechanics won't be the bco's main expertise. So yes ask first.

Probably OK, and I could have proved it 50 years ago.....if indeed it is the case.

 

Could you squeeze a rectangular duct of similar area in instead?

[Temp]

I've got it in my head that stacks must have at least an  80mm (82mm?) diameter AAV?