Soil pipe vent query

[Aragorn84]

We have a cellar/utility space at the side of the house, which contains some plumbing/electrics and the boiler.

In this space is a 40mm waste pipe, which picks up the boiler condensate and the downstairs toilet sink wastes, and feeds them down into a 110mm soil pipe, which picks up the downstairs loo and then heads across under the kitchen floor to the other side of the house.

This 40mm waste pipe then snakes around the ceiling, goes up thru the airing cupboard, before finally exiting thru the roof, presumably as a vent pipe.

The roof terminal is leaking, and i'm going to get someone out to look at it, but i'm wondering if i need to keep this pipe at all? Could i cut it off in the cellar and cap with an AAV?

I'm thinking it might be easier to simply remove the roof terminal all together, if theres no vent it cant leak. But clearly i dont want to break the plumbing system in the process!

I will post some pics of the arrangement

 

[Aragorn84]

 

[Hugh Jaleak]

Is there another vent anywhere else on the property? If there is, you will probably be ok to cap this one with an AAV, if there isn't, you may find you have problems if you cap it.

 

[Aragorn84]

The main stacks are vented at the other side of the house, 110mm goes all the way up thru the roof for those. This vent line just seems to be for the branch to the downstairs loo.

Cheers