P trap AND air admittance for drain?

[CrawfW]

Hi,

I currently have a ceramic pipe leading into my main drain inspection chamber. It is fed by a combined soil pipe and waste water inlet which includes some sort of old P trap/bottle gully.

As part of fitting new toilets, I am adding a new soil stack. I want to connect this to the existing ceramic pipe, replacing the existing arrangement.

When i do so, do i need to add another P trap, or is the air admittance valve alone OK?

Crawf

 

[Nige F]

We need some pics. A soil pipe doesn't have a trap @ the bottom - a waste water stack can do