Air admittance for toilets

[Russell griffiths]

Hi. We have 4 toilets all on the ground floor, the furthest toilet on the drain run has a soil vent pipe in the traditional manor exiting the rear of the toilet and venting up and out like a traditional svp, now the other 3 toilets have been drawn up by our hydrological engineer as having NO venting at all, 

 

 

i personally was going to fit air admittance valves on each stub stack, hidden in cupboards to the rear of all the toilets. 

 

Our baths, showers, basins exit the building in separate pipe work to the toilets. 

 

Any thoughts. 

[PeterW]

Additional cost and complexity that isn’t needed ..?? 

 

Can you not carry the waste on under the wall and out the other side and then it’s terminated with a  vent or AAV there so there is no cold vent in the house..?

[Russell griffiths]

The last vent, a traditional svp is on the exterior of the house and exits under the floor so no cold bridge in the wall or cold vent through the roof, 

Its the other 3 he has said can exit straight into the pipe with no AAV needed, do they not need to draw air as they wooosh away. 

[Temp]

You are allowed up to 8 WC on an unventilated common branch discharge pipe over 100mm in diameter.

 

See Table 2 at top of page 9..

 

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/442889/BR_PDF_AD_H_2015.pdf

 

One option is to build the stub stacks and cap them off. Add AAV later if there is a problem. Insulate around the stub stack in the boxing. 

 

Stub stacks can also be useful for rodding if that ever becomes necessary.

Edited April 28, 2018 by Temp