This water use device is provided with: a water supply unit that supplies water; a water treatment unit that is connected to the water supply unit via piping and that has a function for removing ionic substances included in the water supply from the water supply unit by an electric ion removal means; a water use unit that is connected to the water treatment unit via piping and that uses water which has passed through the water treatment unit; a water discharge pipe for discharging water having an increased density due to the ionic substances removed by the water treatment unit; and a control unit that controls the flow path of water supplied by the water supply unit and causes the water having an increased density due to the ionic substances to be discharged from the water discharge pipe.
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