I just got a quick question to ask how to get drainage information for a flat building? e.g. the mapping of all those main communal waste pipes and how they linked together?
Is it from the developer, landlord, or some sort of archive?
If it is an old flat conversion , no chance . A more modern conversion or building ,possibly the local council , but do not hold your breath. Or freeholder or known archetect
If it’s that new, the company who built it may still have the info. They set it up, and I imagine they would keep plans and records for awhile just in case there’s legal issues.
If the council can’t help you could try asking them directly.
As a start, look up the planning application online on your local councils website. It should have a full architects drawing of the final apportioned building plan - worth checking if there’s anything about the drainage there.