I want to fit a svp

[seagulls]

I have a bungalow style property where the 2 toilets drain straight down into a 110mm drain run under the floor. There has never been a vent pipe fitted and this is causing drainage problems. I have only just gained access to under the floor and the pipe runs and my question is where should I tee off for a vent pipe?

 

[stevetheplumber]

I have a bungalow style property where the 2 toilets drain straight down into a 110mm drain run under the floor. There has never been a vent pipe fitted and this is causing drainage problems. I have only just gained access to under the floor and the pipe runs and my question is where should I tee off for a vent pipe?

idealy it would be at the end of the run to allow a flow of air through all the drains well designed drains with this set up rarely smell realy there shouldnt be two toilets on one run as one can pull the seal from the other each wc should run into a manhole seperately with one of them carrying on to atmosphere as a vent

 

[Bernie2]

Yes! The idea is to allow a stream of fresh air to pass right through the drainage system.

Venting of course above a level where it avoids smells.

 

[seagulls]

Thanks for your replies. My problem is I can only get to the pipework under the floor and theres no chance of altering it now!
Could I tee off from the last stretch of pipework before it runs out of the building and run a new pipe out through the wall and up?