Soil pipe in Victorian terraces/position of second loo

[HangerLaneGyratorySystem]

Does anyone have experience of this - I'm looking at Victorian terraced houses to buy, never lived in a terrace before - am I right in thinking that if you want to put a second toilet in on the ground floor it has to "line up" with the existing soil pipe entry/exit - so you could only install a toilet directly underneath the existing one?

I've also seen some houses where the soil pipe seems to be entirely inside the house - going from, say, a bathroom that is downstairs, straight from the back of the toilet under the floorboards and (I think) runs under the boards to exit the house under the back garden. Does that mean you simply won't be able to connect up even if you installed a new toilet directly above it?

Hope I'm making sense! I need 2 loos!

I need a downstairs loo and I thought you just shoved them under the stairs but NO. That would be too easy. I asked DP to draw up a plan on the back of a fag packet (he used to be in the trade) and he's been doing that negative face thing and mumbling about macerators.

I don't know. My house is quite old -20s rather than Victorian. We have two toilets, one upstairs and a relatively new one downstairs but it's not underneath the other one. They both have a separate waste pipe but I am unsure if they join up underground or not. They are both on the same wall but quite a few metres apart. One is an old cast iron type.

Our current house is 1930s style semi, builder cut an exit in the wall and ran a new soil pipe extension to meet the old one and joined them. But that's because both toilets "exit" onto an outside wall if you see what I mean; hence me saying how do you do that in a terrace? Not sure I'm making this easy to understand without a diagram, but then a diagram of what? I'm seeing 4 houses next week all terraced, all have same issue but different layouts.