Abstract: A method of operating a fluid control system and a distribution valve thereto. The fluid control system comprises a heat source (1) for a heat medium and several distribution valves (6) for distribution of heat medium to several heat consumers (8). Cold return heat medium from each heat consumer is returned to the heat source via a pump (10). To each distribution valve is transmitted warm heat medium from the heat source and cold return heat medium, which are mixed in the distribution valve in accordance with the heat requirement of the corresponding heat consumer. The fluid flow to each heat consumer is constant and is adjusted at the installation of the fluid control system. Thence, the fluid flow is maintained constant and the mixture ratio is adjusted independent of the fluid flow. This means that the fluid flow pump will work under constant flow leading to constant pressure over the pump.