A coil support member is attached to a coil inside a water storage vessel and includes multiple openings, insertion portions and a non-insertion portion. The openings are arranged in a lengthwise direction, and together with surrounding sites prevent contact between mutually adjacent loops of the tube of the coil and suppress contact between an inner surface of the water storage vessel and an outer surface of the coil. The insertion portions are formed between the openings and are inserted into an intra-coil space located radially inward of the outer surface of the coil. The non-insertion portion is positioned in an extra-coil space located radially outward of the outer surface of the coil. The insertion portions have insertion body portions preventing contact between mutually adjacent loops of the tube, and engagement portions contacting the tube from the intra-coil space and maintaining an inserted state of the insertion body portions.