A water quality management system for managing the water quality in a water supply network having water pipe lines running from the purification plant to consumers' faucets to maintain the water quality at the consumers at the terminals of the network at an appropriate level. The water quality monitors for measuring the quality of water in the pipe lines are installed in the small-pipe water distribution network branching from the water distribution main pipe network and running toward the consumers. The water distribution facility for improving the water quality is installed at the base point of the small-pipe water distribution network. The water quality in the small-pipe water distribution network is managed based on the signals from the water quality monitors.