A water circulation system associated with a refrigerant cycle, comprising: a first refrigerant circulation unit where first refrigerant exchanging heat with outdoor air flows to perform the refrigerant cycle; a second refrigerant circulation unit where second refrigerant exchanging heat with the first refrigeraant flows to perform the refrigerant cycle; a water circulation unit in which water flows for indoor cooling and heating in a cooling/heating unit, and for hot water supplying in a hot water supplying unit; an intermediate heat exchanger with three flow passages where the first refrigerant of the first refrigerant circulation unit, the second refrigerant of the second refrigerant circulation unit, and the water of the water circulation unit independently flow through three pipes (15, 26, 61) having a concentric axis and different diameters in order to exchange heat among the first refrigerant, the second refrigerant, and the water; a water refrigerant heat exchanger exchanging heat between the second refrigerant of the second refrigerant unit and the water of the water circulation unit; a water pump; a hot water supplying pipe arranged to guide water discharged from the water pump to the hot water supplying unit and on from the hot water supplying unit to a combine point; a cooling/heating pipe arranged to guide water discharged from the water pump to the cooling/heating unit and on from the cooling/heating unit to the combine point; a main pipe arranged to guide water from a discharge side of the water refrigerant heat exchanger to the water pump, and from the combine point back to the water refrigerant heat exchanger; a branch pipe arranged to guide water from a branch point of the main pipe which is between the combine point and the water refrigerant heat exchanger, to the intermediate heat exchanger, and from the water refrigerant heat exchanger to the main pipe at the discharge side of the water refrigerant heat exchanger; and a first flow control unit installed at a point of the branch pipe corresponding to an inlet of the intermediate heat exchanger to selectively prevent the flow of the water to the intermediate heat exchanger. a first refrigerant circulation unit where first refrigerant exchanging heat with outdoor air flows to perform the refrigerant cycle; a second refrigerant circulation unit where second refrigerant exchanging heat with the first refrigeraant flows to perform the refrigerant cycle; a water circulation unit in which water flows for indoor cooling and heating in a cooling/heating unit, and for hot water supplying in a hot water supplying unit; an intermediate heat exchanger with three flow passages where the first refrigerant of the first refrigerant circulation unit, the second refrigerant of the second refrigerant circulation unit, and the water of the water circulation unit independently flow through three pipes (15, 26, 61) having a concentric axis and different diameters in order to exchange heat among the first refrigerant, the second refrigerant, and the water; a water refrigerant heat exchanger exchanging heat between the second refrigerant of the second refrigerant unit and the water of the water circulation unit; a water pump; a hot water supplying pipe arranged to guide water discharged from the water pump to the hot water supplying unit and on from the hot water supplying unit to a combine point; a cooling/heating pipe arranged to guide water discharged from the water pump to the cooling/heating unit and on from the cooling/heating unit to the combine point; a main pipe arranged to guide water from a discharge side of the water refrigerant heat exchanger to the water pump, and from the combine point back to the water refrigerant heat exchanger; a branch pipe arranged to guide water from a branch point of the main pipe which is between the combine point and the water refrigerant heat exchanger, to the intermediate heat exchanger, and from the water refrigerant heat exchanger to the main pipe at the discharge side of the water refrigerant heat exchanger; and a first flow control unit installed at a point of the branch pipe corresponding to an inlet of the intermediate heat exchanger to selectively prevent the flow of the water to the intermediate heat exchanger.