Answer: In simple terms a sewer serves two or more separate properties. A drain serves a single property. It follows that when drains from two or more separate properties combine then they create a sewer. Sewers are designated "public" when they are operated and maintained by the appropriate sewerage undertaker. Following the transfer of private sewers and lateral drains on 1st October 2011 the majority of private sewers serving more than one property and lateral drains that extend beyond the boundary of a property are now the responsibility of the Statutory Sewerage Undertaker for your area. There are an estimated 37,000 Km of these sewers in the Midlands area alone, many of which have yet to be mapped and therefore may not currently show on the Statutory Sewerage Undertaker's sewer records.