Bathroom soil stack - help with layout / options (with pics)

[danlightbulb]

Hi all,

I have an ongoing dilema with my bathroom waste. It is an internal cast iron stack that comes up behind panelling downstairs and emerges through my bathroom floor, toilet and wastes tee in, and then it carries on up to the loft and out the roof.

Current setup (cast iron fittings):

I want to relocate the toilet about 1.5m to the right. The sink will be above where the toilet currently is. I therefore could do this:

As you can see this pretty much copies what I have now, but with the toilet on the right. Can I bring the bath waste into the bend as shown?

Or I could try this:

But I don't know if I can use the swept tee that way (will poo travel past it and get lodged on the left)?

Of course the new pipework would all be plastic but I have got to connect to the CI with a rubber coupler under the floorboard level somehow.


I just don't know how best to do it.

Are there other options I could consider?
Are there other options for the sink / bath waste?
Am I better off with an air inlet valve or venting out the roof?


All this will be boxed in as I have bought a sit on sink, back to wall toilet and concealed cistern. I intend to build a worktop like area, like the built in furnature but made myself.

Would appreciate any guidance!

Thanks

 

[Bahco]

Firstly, you must vent out of the roof and not AAV.

Use a strap on boss below your toilet connection for the bath and sink wastes.

 

[danlightbulb]

Firstly, you must vent out of the roof and not AAV.

Why?

 

[horhay]

If i was doing the job i would cut the cast iron out and re do the stack in plastic. I would leave it going through the roof. Plastic is easier to work with and gives you more options. Use a rubber union that will suit cast to plastic, use a plastic branch with boss connectors and take the bath and basin waste into the branch using the boss's

 

[Bahco]

Firstly, you must vent out of the roof and not AAV.

Why?

Because sewers have to be vented to prevent build up of methane gases.

Do in plastic as per horhay's suggestion.