PURPOSE: To recover refrigerant solution, precipitated in a pipeline, automatically by a method wherein an automatic opening and closing plug is floated when a given amount or more of the refrigerant solution is reserved near the automatic opening and closing plug whereby the refrigerant solution is dropped into the opening of a recovery device while the automatic opening and closing plug is dropped automatically as the reserved refrigerant solution is reduced whereby the opening of the recovery tank is blockaded.

CONSTITUTION: A recovery device 9 is installed at a place whereat refrigerant solution is reserved as the recovery method of refrigerant solution while the automatic opening and closing plug 13 of the recovery device 9 is formed of a material, whose specific gravity is lighter than the refrigerant solution 3 and heavier than water. When the refrigerant solution 3 is reserved near the automatic opening and closing plug 13, the plug 13 is floated automatically to recover the refrigerant solution 3 into a recovery tank 12, then, the amount of refrigerant solution 3 near the automatic opening and closing plug 13, is reduced and the plug 13 is dropped automatically to blockade the opening of the recovery tank 12. According to this method, the consumption of the used refrigerant solution n3 can e minimized.