Abstract: Disclosed is a pair of check valves for a home solar heating apparatus, one check valve for the solar collector supply line and one for the return line. The check valves have a transparent portion and an impeller which rotates during water flow and is located in the transparent portion, providing a visual check on water flow. Further, the impeller in the collector supply line acts as a check valve element which is gravity closed due to the impeller's greater-than-water density. Analogously, the impeller in the solar collector return line acts as a check valve due to its less-than-water density, these check valves operating to permit the usual direction of flow powered by a circulating pump but impeding the opposite direction of flow powered by thermosyphoning.