A simple graphical method for designing all types of partly full circular sewers is presented. The designing flow rate, velocity, partial depth of flow, and Manning coefficient of roughness are the input parameters for design procedure. The desired design parameters of gravity sewers (diameter and slope) that complying with the conditions of the Egyptian code could be easily estimated. Based on Manning equation two designing graphs for flow in sewers at depths of 67 and 75 percent of the pipe diameter were established. The first graph should be used for sewers having inner diameters up to 700 mm while the other for sewers with bigger diameters. Another graph was provided for estimating both the velocity and the partial depth of waste-water in all types of circular gravity sewers. The flow rate, the Manning coefficient of roughness, slope, and sewer’s diameter are considered as the leading parameters for using this nomograph. The feasibility, ease, and accuracy of this new graphical method were checked and assured by illustrative numerical examples.

Nearly all water supply systems for medium or high -rise buildings in Egypt include storage cisterns to feed the upper floors with cold-water for different uses. Although, these cisterns are the most important component in the distribution system, they are generally the least understood in terms of their effect on water quality. In this study, chlorine residual, algae genus and concentration, and pH value were measured before and after storage cisterns that exist over a 12-floors building in Assiut City to check their effect on water potability, through 48 hours of observation. EPANET quality model is applied to simulate the chlorine residual and water age in the distribution system and storage cisterns through extended period simulations. The applied software implements a Lagrangian time-based approach to track the fate of discrete parcels of water as they move along pipes and mix together at junctions and cisterns. Residual chlorine reaction coefficients for the investigated system that match the field measurements are optimized. The model is used to study the influence of the storage cisterns size and the turnover depth on residual chlorine decay and water age in the tanks. Results indicated that, oversized storage cisterns can have negative impacts on water quality, including increased water age, reduced disinfectant residuals, and increased growth of disinfectant by-products (DBPs). Some of the microbiological and chemical effects of the cisterns on water quality have been investigated. More researches are needed to check DBPs levels in the water leaving such storage cisterns.