Soil stack

[franky]

I have a complicated soil stack to do and am a bit worried about the venting of it.
The house I'm doing has three bathrooms but 4" Waste for the top floor drops down 3m internally then out into the external soil. am I right to be worried that this pull the traps. if I drill out a 2" vent to outside do you think this would be ok or am I just being a bit ott
Thanks

 

[SafeGasInstall]

Just fit 4" air admitent valve at the highest point of the stack and will be ok

 

[franky]

I can't because of the bathroom setup theres no place so I also cant get a 4" out on the top floor but I can get a 2" out so was think of using that as a vent

 

[SafeGasInstall]

2" is not big enough mate

 

[SafeGasInstall]

I did mean 2" air admitent not big enough

 

[SimonJohns]

Do you have to go external?. Why can't you like safegas has already said, fit a durgo/ air admittance valve?

 

[PlumbBobBob]

you can get durgos now that can go below the flooding level, would one of these do?

 

[SafeGasInstall]

Really stave ? Pls post a link

 

[PlumbBobBob]

looking for one stan although just found that as long as they are to BS EN 12380 designation A1 they are allowed to be used below flood plane.

 

[PlumbBobBob]

have a look in here http://www.mcalpineplumbing.com/media/cat/36.pdf

 

[Howsie]

Is it the primary stack?

 

[Guest123]

The new A1 rated AAV's from Floplast and on sale from Screw fix can not only be installed below the flood level of the highest appliance, but there is a version that can be installed externally and won't freeze and has mesh to stop insects and pests from gaining entry. I've used these a lot and they are really good quality, unlike the waste pipe and fittings Floplast normally make.

 

[franky]

I was thinking to drill the 2" out and into the primary stack but the 4" would go down 3m across 2m and then out into the primary stack. This would vent it like they used to do years and years ago but i'd prefer to be safe then sorry