ABSTRACT
The storm water flow is many times greater than the quantity of foul sewage carried and, in fact the sewer is designed as a storm water drain. The size of pipe required tends to be very large in serving a district and to reduce this ‘storm overflows’ are provided. When the storm flow exceeds a predetermined limit, these overflows discharge the excess flow to a convenient watercourse, and permit the use of a smaller pipe size. The overflows are designed to operate when the flow in the sewer exceeds six times the dry weather flow. However, the discharge of the mixture of foul and storm water causes pollution of the watercourses and is a serious, and nowadays unacceptable, fault in the system.
