PURPOSE: To prevent the freezing of drain, and to increase the speed of exhaust, by using sn exhaust valve that a caliber of an air flow path is large and there is no bending portion in the air flow path.

CONSTITUTION: When a liquid level in a tank 1 does not reach an upper limit, a contact b of a level switch 71 is under a closing condition and a contact a is under an opening condition, a solenoil 22 remains as it is demagnetized - that is, an intake valve 2 remains as it is closed - a solenoid 322 is excited and a pinch valve 31 of an exhaust valve 3 is opened. Thus, liquid L in tank T flows into the tank 1 while opening a check valve 4 by the water head. Since gas in the tank 1 is discharged through the pinch valve 31, which is manufactured so that a sleeve in rubber be opened and closed and which caliber is large, in a liquid admission process, drain is not collected while frost is blown off every exhaust even if frost is formed on an inwall of the sleeve, frost does not grow and freezing is not produced.