The Bureau of Waterworks of the Tokyo Metropolitan Government puts stable water supply as a most important element in its management policy and puts the following measures into practice: measures to meet long-term water demand; development of water resources and the expansion of the supply network and purification facilities; effective utilization of water, realization of the Bureau's aim to make Tokyo a water conservation conscious society; more stable and efficient water supply; general improvement and technical innovation of facilities and supply network; improvement in leakage prevention measures. It has been challenging to realize these measures within a short term, because the Waterworks in Tokyo is one of the biggest water supply systems in the world. The Bureau has systematically worked on these measures and has been getting steadily improved results. This paper describes some recent achievements and future policy concerning the water distribution system and its improvement.