In response to the "Water Pollution Prevention and Control Action Plan" promulgated by the State Council and to achieve the goal of direct drinking of municipal tap water in 2035, the secondary water supply net- work of an old community in Shanghai is simulated. According to the current pipeline network layout, three other different pipeline network layout schemes are proposed, which are simulated to compare the water age, pressure, flow rate and other hydraulic conditions at each point. Choosing a more appropriate transformation plan and comparing the current situation and planned one, the water level of the pool and the diameter of the pipe network are respectively optimized. The simulation results show that the water level optimization and pipe diameter optimization of the pool can significantly shorten the water age, and the pressure and flow velocity are in a more appropriate range. According to the simulation results, the multi-dimensional comparison and selection are finally selected based on the current situation of the optimization of the water level of the pool and the pipe diameter. After testing, all water quality indicators are up to standard after the renovation, and the residual chlorine attenuation coefficient is reduced by 53.3%.