Advice needed pipe size and where to change

[daro6789]

hello all pretty new to the forum and was after some advice.
I am fitting a new bathroom/wet room in a house I have just bought and wanting to move the waste thus putting a new length in and a boss onto the 4inch soil that is set in the concrete floor. My question is am I ok to run the 1 1/2 pipe from shower to pick up the bath then into the boss a length of about 3 metres concreted int the floor or should I extend the 4inch as far as I can under the bath and shower then just drop down with the smaller pipe into the 4inch.??? Would it make a difference either way?

I have taken the concrete up in the room as to get the wastes where I want them.

 

[ShaunCorbs]

tbh you would be better installing 2" if your going to tee the bath into the shower waste

 

[daro6789]

Ah ok so the 2onch would be better to take them both and would be ok concreted back in then.

 

[ShaunCorbs]

Ah ok so the 2onch would be better to take them both and would be ok concreted back in then.

yes as-long as its supported