That is a nice idea but unfortunatelying not, it does back on to an outside wall however it is directly above an angled roof over the extended ground floor part of the house. Running a pipe on the outside of that wouldn't be ideal and would displease the wife hugely.
I can see how that would work, except it takes me back to the original restriction of not wanting to rip out the bath - it's very well integrated with tiled side panels etc.
I have just short of a foot of accessible soil pipe between the end of the bath and the toilet itself, ideally what I'm looking for is something that will integrate into that area to help encourage a better flow. I have seen the Saniflo products but don't have a full understanding and wasn't sure if there was one that met my criteria.
I don't mind a bit of routine maintenance, especially a 20 year one as you mentioned.
I see what you mean about the cap at the end of the bath. It is a shame, such a daft problem really.
The soil pipe is enclosed on the left hand wall. This was originally an outside wall but the house has now been extended on both floors so it is encased in a boxed in wall section within a new room.
So the lay out is soil pipe, wall, bath (lengthwise) then toilet. The back wall is outside but directly above an angled roof section with skylights. There will be a supporting wall/ lintel directly underneath too.
All in all nothing is accessible too easily (sorry!).
The Saniflo could do it but that leaves me with the challenge of running a vertical pipe from the toilet, and somehow breaking back in to the soil pipe from above. With the above info in mind, this sounds worse than moving the bath out. Even if I went for ripping the bath out, I may end up having to lift this higher than it is already, which won't please the kids.
Really sorry, it's not an easy one is it? I'm trying to think of the easiest and cheapest option, but also don't want to compromise the the aesthetics of what is otherwise a lovely bathroom.
I think it might be accessible from the other side I guess. The room to the left formerly the outside wall, has the boxing of the pipe there. This could easily be cut into in order to gain access. I don't know what the roof access would be like but it might be possible. The final factor would be chasing a vertical pipe into the wall from behind the toilet - that's my least favoured part of the plan, but the alternative of having visible pipes isn't an option for me.
I'll have to find a local plumber to discuss this further with, I also have mixed feelings about using the original guy under the circumstances even though I'm still in touch.