Conventional automatic production flow control and pump pressure control of water supply systems are robust and simple: production flow is controlled based on the level in the clear water reservoir and pump pressure is controlled on a static set-point. Recently, more advanced computer-based control methods were developed in which production flow is controlled by using a short-term water demand forecasting model and pressure is controlled by a dynamic pressure control module. To assess the differences between conventional and advanced control, we examined operational data of water treatment plantGruszczyn that supplies drinking water to a part of the city of Poznań, Poland. We compared two periods of three weeks of conventional and advanced control. The comparison showed that with advanced control the variation in the production flow was 83% lower, and the pump pressure of the clear water pumps was 29% lower. The lower pressure resulted in 20% less background leakage and the overall system's energy costs were 11.5% lower.