What is the legal sewage pipe size for a single house?
I have a main Thames Water sewage pipe running through my property, which takes both foul water and surface water. My neighbour's pipe (225mm at present) joins into this main pipe. We need to, for renovation purposes, change the route of this pipe. This process would include replacing the pipe from his side to the main pipe in our house. He is insisting that we replace his 225mm pipes with the same size pipes, however I have been informed by my builder and surveyor that a 4in (110mm) pipe is sufficient to take the full load of his house. We are interlocked in a dispute at the moment, so my question is, what is the legal requirement of a sewage pipe diameter in the UK? Can we install a 4in pipe, or do we have to comply with his demands? Any help would be greatly appreciated, as it seems that all newdevelopments nowadays have 4in pipes, but I have no legal knowledge.