A main sewer is a larger diameter underground pipe that collects flows from numerous lateral drains and branch sewers and conveys them to a sewage treatment works. In Greater London the main sewerage network is owned and operated by Thames Water and includes both Victorian brick-built interceptor sewers and modern concrete or HDPE replacements. Main sewers may be gravity-driven or, in low-lying areas, supplemented by pumping stations and rising mains. Capacity is governed by population, expected rainfall and combined or separate system arrangements. Maintenance is carried out under the Water Industry Act 1991 and includes desilting, root cutting, relining and CCTV monitoring. Connections to a main sewer from new developments require formal approval and are typically made under a section 106 agreement.
Sewer (main)
Large underground pipe carrying combined or separated wastewater from many properties to treatment.
