Building regs for soil stack change

[grants]

I'm thinking about redoing my bathroom. I'm pretty sure that what I would want to do will require changes to the soil stack. It would be in the same place and run into the drains at the same place, but I'd need a new pipe coming into it from the other side of the bathroom. It's an old cast iron soil stack.

Does anyone know:
- if I make this change do I need to get building regs approval?
- if I want to change any part of the soil stack do I need to replace the whole old soil stack with a new plastic one?
- if I want to change any part of the soil stack do I need to fit a vent at the top?
- are there any special requirements for the new connecting pipe to the old soil stack?

First time user, all help gratefully received.

 

[Goldberg]

You don't need LABC approval to replace old items with new ones.

I don't believe you need LABC approval to lengthen the soil branch from an existing WC.

You don't have to change the entire cast iron stack, but depending on the extent of your changes you might find it easier to replace it.

You don't need to change the venting arrangements if you're not adding a WC or changing the point at which it connects. Adding a vent at roof height might do nothing, but it can't possibly do any harm.

 

[OvertonPlumber]

Oki the easiest thing to do is cut the soilpipe below the branch with a 9" grinder it wont cut all the way through will leave about 1/2 inch you can get that tobreak cleanly with a swift tap with a club hammer. oh i am getting ahead of myself.
open up the drainhole and plug the base of the stack then start to dismantle the stack down to the part you wish to cut it at. the collars will break quite easily if you hit them with a club hammer. I normally insert a plastic bag into the soil as im working my way downto avoid getting broken bits down the soil. be aware cast soil is very heavy especially if you up a ladder!!!!! work in small pieces.oki Once you cut the soil, you can get a rubber joint they
http://www.diydoctor.org.uk/project_images/svp/3.connectionsleeve.jpg
i normally whack some clear silicon on the soilpipe as well.
You can then build up your soil in plastic.
All stacks need ventilation, for s.hit to go down air must go in. However it is only nesscary to ventilate one soil pipe on ecah drain run to high level air, the rest can be terminated internally on durgos. If your stack is internal it would make sense to take it to air.

http://www.diydoctor.org.uk/projects/soilandvent.htm

^^^ might help you