This paper discusses several sequential steps to developing and implementing an effective microbial control program for a distribution system that include: an initial distribution system survey; unidirectional flushing; implementation of a distribution system Code of Practice; and, modeling. The purpose of the initial survey is to identify all potential problem areas within the system. Flushing is the single most powerful tool available to consecutive systems in their effort to maintain water quality control. Unidirectional flushing consists of isolating a particular pipe section or loop, through closing appropriate valves, and exercising the hydrants in an organized, sequential manner to produce velocities of 6 fps or more. These high velocities produce a scouring action which remove accumulated debris, biofilms and/or corrosion products. However, the flushing program will not correct all deficiencies or problems in the system and should be incorporated into an overall Code of Practice. Criteria included in the code is discussed.