Minimum distance of branch pipe from top of stack

[Rzzrmeanr]

Hi,

I'm connecting a 110mm branch pipe to the main stack the top of which is in the loft (sealed with a air admission valve) however the likely connection point will be about 20 inches from the top of the stack.

Is there a minimum distance from the top of the stack any branch connections must be?

Thanks

 

[Riley]

Don't think there's a minimum however the AAV should terminate higher than the highest over flow point

 

[Rzzrmeanr]

Don't think there's a minimum however the AAV should terminate higher than the highest over flow point

Do you mean terminate higher than where the branch pipe connects to the stack? That would surely be the case, otherwise the branch pipe would be pouring soil into it

 

[Riley]

I'm assuming you are installing a bathroom /toilet? If you have a basin the AAV must terminate above the overflow of the basin