To prevent freezing of residual drain in drain discharge for heat source equipment used for hot water supply, heating, additional heating of bathtub water or the like.

This drain discharge device for heat source equipment (a heat source equipment unit 4) including heat exchangers 44 and 74 generating drain by heat exchange comprises a drain tank 92 storing drain(D) generated by heat exchange in the heat exchangers; a water level detecting means (level sensor 106) detecting the level in the drain tank; a drain circuit 80 guiding the drain in the drain tank to the outside; a pump (drain pump 94) forcibly guiding the drain to the drain circuit; temperature detection means (temperature sensors 88, 98 and 145) directly detecting the temperature of the drain, or detecting the temperature of a portion related to the drain temperature; and a control means (control device 154) driving the pump, in a case that the temperature detection means detects a predetermined temperature or lower, and the level detection means detects a predetermined level or more, to forcibly discharge the drain in the drain tank through the drain circuit.

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