The manual is to serve as a guide to Public Health Service engineers in evaluating the sanitary features of water supplies with which they are concerned. The text is divided into four sections. Part I gives those features of water-supply systems which are of sufficient importance to be included in a sanitary survey, and lists major sanitary defects and health hazards, which, if present, would be detrimental to the safety of the water supply. Parts II and III deal, respectively, with recommended sanitary requirements for water treatment and for water-distribution systems. Part IV has been added as an explanatory discussion of the bacteriological and chemical requirements for potable drinking water as set forth by the 1946 Public Health Service Drinking Water Standards.