Under Section 104 of the Water Industry Act 1991, a developer may enter a voluntary agreement with a sewerage undertaker for the adoption of sewers serving a development. A specific condition of a Section 104 agreement is that the new sewer development meets Mandatory Build Standards (MBS), which set out the required standards in the design and construction of new sewers and lateral drains.

Once the sewer has been constructed to an agreed standard, the new sewer is then adopted by the Statutory Water Company. Adoption of a new sewer means that the Water Company will maintain the sewer for the foreseeable future, and at the publics’ expense.

The relating Section 104 Agreement bond is calculated at 10% of the estimated construction cost of the sewers (33% in Wales).