Abstract: A hydronic heating system having a source of hot supply water and a reservoir of cooler return water, a supply water line from the source, a return water line to the reservoir and a multitude of heating loops through which water flows to deliver heat, including: a main distribution station having a supply header, main heating loops, and a return header with a pump compelling circulation within the main station so that heat from the source flows to the main heating loops; and one or more satellite distribution stations, each with a supply header feeding water to satellite heating loops, and a satellite return header and pump compelling circulation within the satellite station; and a satellite injection water line and return water line for circulating some hot water from the main station to each satellite station so that heat from said main station flows to each satellite station.