The manual is intended to serve as a guide to officials of local public agencies in evaluating sewer construction practices and in making field surveys of infiltration of ground waters and inflows from various sources. Guidelines are also presented for making economic analyses of the cost of excessive infiltration and inflow, and for instituting corrective action. The problem is especially serious in the case of sanitary sewer systems in urban areas. Such systems are designed to carry only sanitary wastes, and a reasonable standard allowance is made for unavoidable entry of ground and surface waters. The illegal connection of roof leaders and foundation drains to sanitary sewer systems is the principal source of inflow. Improvements in inspection of construction and testing of completed sewer lines will promote the use of better materials and good construction practices. The use of air for infiltration testing and water for exfiltration testing is described. Exerpts from sewer control legislation are given. Codes, standards, specifications, and suggestions for sewer design, construction, inspection, repair and cleaning are discussed.