Abstract: A vacuum feed system for feeding liquid chemical into a stream of a second liquid flowing in a conduit includes a venturi connected in the conduit for supplying vacuum through first and second one-way check valves, a flow regulating valve, and a vacuum regulated flow control valve connected to a supply of liquid chemical to be fed. A pressure relief valve connected between the first and second check valves prevents back flow through the system. The components of the system, from the vacuum regulated flow control valve to the venturi, are arranged to provide a continuous upward flow path to thereby eliminate trapped gas in the system.