The dynamic properties of district heating (DH) systems includes water flow rate and heat propagation from heat production plant to consumers. Reduced heating water flow rate was estimated in Riga city district heating system net during heating season of year 2008/2009. Such decrease in flow rate can be explained with reducing of heat losses of buildings as well as more economical usage of heat energy. The objective of this paper is to investigate the possibility of successful heat transition from DH plant "Vecmīlgrāvis" by decreasing of the supply temperature of water from the temperature graph 130/70 °C to the temperature graph 115/70 °C. At the same time, the reliability and quality of the heat distribution to the customers must be kept unchanged. The flow ratio depends on the heat demand and the temperature of the hot water supply. With the goal of keeping the output temperature from DH plant as low as possible, it is necessary to determine the upper limit for the flow on the DH network, which depends on pipes diameters, technical condition, pumps etc. Operational data from the DH plant "Vecmīlgrāvis" were used to estimate theoretical calculations in this paper.