Our house plot and layout is complicated but essentially it is build into a slope, where the upper floor is above the mains sewage pipes and the lower floor is below. Currently the kitchen and main bathroom are upstairs and so no issues with mains drainage via gravity as usual. If we wanted to build an extension with the kitchen on the lower floor, we would need to install some sort of pumping system to be able to pump away waste water. Either a saniflo type (not keen) or a more powerful pump situated externally. Does anyone have any experience of these?
Alternatively it has occurred to me, could we have a septic tank arrangement for the waste water from the lower floor and keep mains drainage for the upper floor - is this sort of combination arrangement possible?
At a very early stage of trying to determine what would be possible with an extension, would appreciate any thoughts.