This publication describes the processes involved in the design installation and maintenance of modern plumbing systems. It recommends a number of plumbing system design and installation specifications that have demonstrated their validity from years of experience. It also examines the microbiological chemical physical and financial risks associated with plumbing and outlines the major risk management strategies that are used in the plumbing industry and emphasizes the importance of measures to conserve supplies of clean water. This work is dedicated to assisting developing countries in achieving the best possible plumbing levels to ensure the highest health benefits from use of sound plumbing practices. It is aimed at administrators and plumbers working in areas that are served by a mains drinking- water supply or sewerage system or are about to install a mains drinking- water supply or sewerage system. It should be of particular value to those working in countries or areas that are in the early stages of introducing modern plumbing systems. While it draws attention to the problems of drinking- water supply and waste removal in developing countries and outlines some of the strategies currently used it does not systematically cover issues specific to developing countries.