Householder Steven Williams is warning others of the extra costs of building an extension after having to dig up his garden to divert a sewer.

Mr Williams, 58, of Southleigh, Bradford on Avon, wanted to build a two-storey extension but it overlapped the line of the sewer so he requested a build over.

This was refused by Wessex Water and they told him he would have to divert the sewer, despite them having no records of the pipe.

Mr Williams, a business consultant, said: “I am updating their infrastructure at my expense to make it easier for them to access in the future.”

He said he had to pay Wessex Water a £5,000 surety fee and paid £500 for the diversion application and evaluation but no one came to do a site visit.

Wessex Water also told him he would have to divert a storm drain running under the extension, which would have cost him £10,000. Mr Williams had to pay for a CCTV survey on both pipes but, after insisting the firm made a site visit, it was found the storm drain belonged to Wiltshire Highways.

He said: “All the expense and liability has fallen on my shoulders.

“They are treating a domestic customer the same as a large scale developer.”

Wessex Water said the work was needed to protect the sewerage network and ensure it remained accessible.

The company has offered to reimburse Mr Williams the £5,000 surety fee, the application fee and legal fees.