ABSTRACT
WHEREAS the design of surface water sewers is dependent on rainfall intensities and the extent of the catchment area, rates of flow of foul sewage are dependent on the distribution of the population and on the rate at which water is used. The average flow is called the'dryweather flow' (d.w.f.)and is the average rate of flow of domestic and industrial wastes, together with any infiltration, measured after a period of seven consecutive days of dry weather during which the rainfall has not exceeded 0·25mm.
