Internal bathroom pipe advise

[adamt]

Hi there I'm doing a full bungalow renovation with extension.

Due to design constraints the two bathrooms are internal. 

Would anyone have suggestions on the best way to run the soil pipes from the attached pictures. I have plenty of fall. My concerns are at the top end where I was planning on using a y branch with 45 for the toilet to allow the run to carry on to the bath and vent stack at the far end of the room. But have been advised that might not be best practice. The other option its to do as pictured. There's also a 30 degree to get the runs out of the  rooms and a 15degree before they exit the external wall. I believe these slight changes in angle are classed as roadable?

Thanks Adam 

[adamt]

[Mr Punter]

You can run the bath and basin in normal waste pipe.  You could have a waste manifold near the WC to connect everything to. https://www.screwfix.com/p/floplast-push-fit-4-boss-single-socket-waste-manifold-black-110mm/40832

Plus a stub stack and AAV.  This should mean just 1 pipe run out.

[adamt]

Thank you. Bath and basin I may be able to achieve the fall using one of the manifolds. 

The ensuite shower will be to low to achieve the fall using a manifold my idea was to branch in as shown.  I currently have each room on there own pipe.

[Mr Punter]

I would run your proposals past the Building Inspector.  You need to be able to rod all the pipe without disconnecting the WCs etc.

[saveasteading]

Plus, when you have positioned it, gently place and shove a golf ball at the top of the run (not dropped in) and see if it goes all the way.