If South Staffs Water is responsible for billing for water and sewerage services in my area why don’t their plans show their public sewers?

South Staffs Water is a water only company, responsible solely for providing drinking water to their customers. They have no responsibility for providing sewerage services.  Severn Trent Water is the responsible sewerage undertaker in this area. As such, South Staffs Water plans contain only their water assets and public mains water pipes and Severn Trent Water provide separate plans showing the public sewers in the area. However, because South Staffs is required to bill the property for water services they also bill for sewerage services on behalf of Severn Trent Water.