My son is fitting this close coupled basin toilet (below) into a newly created downstairs cloakroom. He started to trench the floor to take a full size soil pipe (4 metres long!) but we stopped him! He's now got a nice deep trench - too shallow for a soil pipe but plenty for a smaller pipe - and we suggested he fits a saniflo (usual objections about noise and cost). However he also want to put a dishwasher into the same outflow. Seeing at there is enough space in the trench, is he better off putting the dishwasher waste in separate pipe to run parallel and sorting out the pipes outflow once it's outside the house, or joining the dishwasher waste after the saniflo but before it goes under the floor? And, what's the best saniflo to choose for this situation?