Abstract: A solar heating system includes an array of solar collectors and a manifold through which the collectors are supplied with water, this water being derived from a storage tank located below the collectors. The water is circulated through the collectors by a pump, and within the collectors the water is heated, but when the pump is not operating, the water drains from the collectors into the tank so it will not freeze and damage the collectors. Each solar collector includes a housing, a collector panel in the housing and containing a cavity through which water is circulated, supply and drain pipes which extend the full height of the housing behind the panel and are connected through ports with opposite ends of the panel cavity, and a light transmitting material over the housing. The supply and drain pipes of some of the collectors are plugged into corresponding supply and drain fittings on the manifold at bushings which fit into aligned ends of the pipes and fittings.