Drains for new wc/shower room

[Racediagnostics]

Hi, I'm new here, first post. I'll apologise in advance for not knowing or using the correct terminology. I haven't done much DIY plumbing for 30 years since I put in a central heating system to an old cottage.

I am planning to put a new shower room/wc/basin into the right hand end of the room below, the new partition wall will be just to the right of the large window, to the left of this will be a utility room with a sink and washing machine.

The existing utility sink/washing machine drains out of the wall and into the 3 inch vented soil stack on the left of the picture.

I plan to dig up the base of this tomorrow to see if it opens up into a full size drain pipe below ground level. If it does it will make my life easier. If it is then I will change to stack to 100mm and go with the plan below.

For the new shower room I will connect the shower and basin on a 50mm branch and bring through the wall together and connect that into a new 100mm soil pipe from the WC. I will also connect up the utility room sink/washing machine to this too as shown in the diagram below.

I will also relocate the rainwater drain pipe to the right hand end of the building so its not in the way of the soil pipe.

So my question is, is this allowable in the current regs and will I need to add any AAVs.

Thanks for any advice you can give.

 

[Racediagnostics]

Well it is a non starter, I dug up the bottom of the stack and found it went to a P gully trap.