Path for soil pipe from bathroom

The toilet soil pipe will emerge from the wall at the green point marked in the diagram below. This is within the kitchen roofspace.

The two alternative pathways to connect this to the main downpipe are via the red path which would mean a hole would have to be cut through the roof slates. Can the roof be effectively sealed once cut through in this manner?

The second route is via the blue path. The pipe would travel within the kitchen roofspace then down and through the kitchen ceiling and immediately corner and through the external wall. Therefore an elbow would be visible within the kitchen. Perhaps more chance for blockage.

Which would you suggest is the best path?

Thanks!

 

I'll measure it, but I think the top of the soil pipe would be at least 30cm below where the top of the external roof ridge is.

The toilet can't be located anywhere else in the room (room dimensions: 1.4m x 1.7m).

I don't think it's really possible to run the soil pipe inside the room first before exiting at a better location due to the size of the room. I want to get a 1.4m long bath, a basin and a toilet in there, so there just isn't the space to run a soil pipe along the wall. Also running the pipe under the rafters isn't an option either due to the rafter direction.

With this being the case, is the red path the preferable option (due to possible blockage issues with the blue path)? It's at the back of a terraced house with a yard, so there won't be any issues with respect to anyone sitting in a back garden and observing that it emerging from the roofspace is unsightly.

 

The bath waste won't be a problem as it would emerge from the wall further to the right on the external wall (observed from outside) so would be clear of the kitchen roof.

The waste from the basin, being much narrower pipework than toilet soil pipe just runs under the floor. There are notches already cut in the rafters from some previous time.

The image above, is that a standard toilet to wall connector - standard diameter?

 

I've just realised there is potentially a third path the soil pipe could take.

The soil pipe would still emerge from the same point on the wall within the kitchen rood cavity (same green spot as per first post). The soil pipe then takes a path within the kitchen roof cavity ( yellow path). This then emerges through the kitchen wall at the second green spot (there's no window on this wall). This path means it doesn't emerge through roof slates, as the red path did in post 1.

There is a manhole cover (red square) and an old outside toilet (red box) just outside, so presumably the soil pipe could go down into the ground and be connected up to the sewer pipe. This would require some digging up of the concrete ground.

Also, it would mean the soil pipe is not going into the stack on the wall, which is open at the top to permit release of gases. I don't know if an open top stack is permitted at the reduced height where it emerges at the second spot on the kitchen wall?

 

Unfortunately the outside loo is as small on the inside as it is on the out.