Central hot water piping systems are used in large lodging buildings (e.g. hotels, dormitories, etc.) for comfort and convenience. However, the big problem to this type of system is that once the hot water leaves the storage tank and travels through the system piping, the water temperature drops due to the travel distance and ambient air temperature. Because of this drop in temperature, users need to wait for the undesirable cool water to flow out of the system before the desired hot water starts flowing out of the system. The ideal solution to this problem is to reheat the undesirable (cooled) water in the system by the use of an individual hot water circulating system. This study focuses on water saving and energy consumption in the individual hot water circulating system. The results show energy consumption is 50% less than the non-circulating central hot water system. Three parameters in wasted water demand, electric consumption, and heating source consumption were considered to transfer them with CO2 transfer coefficient to estimate the reducing CO2 emission. The hot water circulation system presents the benefits of water and energy saving, and reduction of CO2 emission, but the piping connection should be improved for easy installation in the existed buildings in the future. (C) 2014 Elsevier B.V. All rights reserved.