A valve system for monitoring and controlling a flow of a fluid additive into a main fluid line is disclosed. The system includes a pump that provides a constant flow of the additive from a fluid reservoir through a supply conduit into the main fluid line. A portion of the fluid additive may be diverted into one or more return conduits leading back to the reservoir by opening a solenoid actuated valve in the return conduit. Flow meters are employed to detect the flow rates of the fluids in the supply conduit and the main fluid line. The flow meters provide signals to a control system, which are effective to control the operation of the solenoid actuated valves to maintain a desired flow of the additive into the main fluid line.