This paper is to make it possible to check geothermal heat-pump performance by using building running water heat-source, a energy we never make use of. To check heat-pump performance, geothermal heat-pump 3RT, heat exchanger 100 m (￠12mm of PE) in water tank, and Vertical heat exchanger 100m (￠32mm of HDPE) were set up in Mock-up House. In fact, heatpump 3RT needs vertical heat exchanger 150m. The experimental results are that in winter season around 0.67RT was taken off from water tank and the rest 2.23 RT was from vertical heat exchanger while using domestic water (710 liter/day, based on 4 people) from water tank During the time of checking, geothermal heat-pump COP was at 4.2, which is enough to meet the standard of national geothermal heat-pump COP, 3.45. It depends on the amount of water supply, but It can be reduced to about 50m of vertical heat exchanger in Residential building so that you can save 20% of the total construction cost. In the future, the study on how to make optimal design in accordance with heat exchanger quality and shape in water tank.