I'm looking for some advise. I recently purchased a house (11 yrs old) and found that the shower tray in the ensuite does not drain very well, although it's build up to a good level. I've cleaned out the traps, rinsed drain pipe with all sorts of drain blockers, still no luck. Breaking into it all, I've now found that the drain from the shower runs about 4-5 meters (with 4 bends) before connecting into the main soil pipe and also, it does not have any fall (slope) in it. The soil pipe is internal to the property and not visible from outside.
Have now decided to put a new ensuite in and I have been through various options with several plumbers, friends, etc and the way-forward looks like installing a new shower tray on the floorboard, with the waste running underneath the floor board and then exiting the property through the exterior brickwork. Once outside, this waste will need to be connected to a sewer manhole about 0.75 m from the exterior wall. The sewer manhole and the internals are all PVC. Yes, I've thought about air-venting, timber supports under floor-boards, etc.
My question is very specific - how do I go about connecting the shower waste (2" pipe) into the sewer manhole? Is this allowed, will I need planning permissions? What are other options?