An OTS is more convenient to use and provides better temperature-controlled water than a natural circulation system. An excellent way to control the exit-water temperature of an OTS is to utilize a PCTCV. Our results show how the average water temperature changes with insolation and collector inclination angle. The measured collector efficiency is close to 60%, while the overall efficiency for the system including the storage tank is relatively low due to poor thermal insulation and large heat capacity of the storage tank. Calculated results agree with experimental measurements.