Effluent ground water overflow in deep and broad ground space building. Temperature of effluent ground water is in $12{sim}20^{circ}...$ annually and the quality of that water is as good as well water. Therefore if the flow rate of effluent ground water is sufficient as source of heat pump, that is good heat source and heat sink of heat pump. Effuent ground water contain the thermal energy of surrounding ground. So this is a new application of ground source heat pump. In this study open type and close type heat pump system using effluent ground water was installed and tested for a church building with large and deep ground space. The effluent flow rate of this building is $800{sim}1000;ton/day$. The heat pump capacity is 5RT. The heat pump heating COP was $3.85{sim}4.68$ for the open type and $3.82{sim}4.69$ for the close type system. The system heating COP including pump power is $3.0{sim}3.32$ for the open type and $3.32{sim}3.84$ for close type system. This performance is up to that of BHE type ground source heat pump.