When I bought the house, why didn the search or survey reveal that it was connected to a private sewer?
Perhaps your solicitor did not ask the right questions or perhaps it was not part of your surveyor’s brief. A standard search of the Local Land Charges Register should reveal that a house is connection to a public sewer, if that is so, but not necessarily whether this connection is direct or via a private sewer. Plans might show the public sewers but not usually private sewers and drains.