Abstract: An automatic shutoff drain remains open to allow the flow of aqueous liquids, but automatically closes if a non-aqueous liquid enters. The drain has four primary components: (1) a conduit having an inlet and an inner orifice; (2) a closing member having an open position that is spaced apart from the orifice to allow the flow of liquid through the conduit and having a closed position that seals the orifice to prevent the flow of liquid through the conduit; (3) a fusible link made from a material that remains intact when immersed in water and that degrades when immersed in a non-aqueous liquid; and (4) a mechanism that restrains the closing member in the open position when the fusible link is intact and allows the closing member to move to the closed position when the fusible link degrades.