My 1950s mid terrace house has a WC on a half landing at the front of the house & discharges into a combined sewer/drain at the front. The bathroom is upstairs at the rear & drainage from the bath & sink, drain into a drain at the rear. First question, is it likely that the bathroom drains go under the house & into the combined sewer/drain? secondly if so could I install a WC in the bathroom to discharge into the drain incorporating the correct pipework etc. I would be using a qualified builder/plumber.