Coonnecting sink/bath wastes into soil pipe

[tonyb61]

My son is putting in a bathroom upstairs in a small victorian house. A plumber has installed a soil stack, and wc connection a while ago, but we now need to connect up a sink waste and a bath waste into that soil pipe. Where the waste pipes would naturally come out of the wall around floor level, the soil pipe has the wc connection....
So I need to come through the wall and drop down 6 inches or so before running the waste pipe along the outside wall at the required fall ?
Here's a photo showing the soil stack. The other question is the sink and bath waste will come into the soil stack on opposite sides, is there a boss(es) that would make that connection easier ?

Thanks
Tony

 

[JCSPLUMBING]

A short boss pipe or strap on boss.

 

[plumben]

if your connecting on opposite sides stagger the height of two strap on boss's

 

[tonyb61]

OK I can stagger the boss's. But in answer to my first question is it acceptable to have a short vertical run of waste pipe on the outside wall so that the long horizontal run is at the appropriate fall ~ 25mm per 1m ? Or is it ok to have an horizontal fall that is much more, say 50mm per m to the place I can put the strap on boss ?

 

[Riley]

As long as you have the fall perfectly acceptable.

 

[tonyb61]

So for sink/bath wastes, as long as the horizontal runs are within the Part H recommendations for fall all is ok, and using a small vertical fall is fine to get the horizontal falls within spec ?