Occasionally when adding a conservatory or orangery the issue comes up about building over a drain. Sometimes it is permissible to build over a manhole or drain.  However, this depends upon whether your sewers are adopted by the water authority. If you are unsure then please contact us.  Alternatively, follow one of the useful links below.  Please note that while there is one water authority in Wales, in England this may vary from among providers. Below are links to advice and guidance from Dwr Cymru Welsh Water, along with Thames Water.  Both are highly regarded in this field: Dwr Cymru Welsh Water http://www.dwrcymru.com/en/Developer-Services/Changes-to-Sewer-Adoption-and-Connection/Sewer-Adoption-and-Connection-FAQ.aspx Thames Water http://secure.thameswater.co.uk/dynamic/cps/rde/xchg/corp/hs.xsl/693.htm