Abstract: A drain plug for axial insertion into a conduit having an inner surface, including a cup-shaped resilient sealing member having a closed end and an open end and having a sidewall having an outer surface conforming to the inner surface of the conduit and with the cup-shaped member normally axially slideable into the conduit, first means intercoupling the closed and open ends of the cup-shaped member for axially compressing the cup-shaped member to flex the sidewall radially outward to engage and seal against the inner surface of the conduit, and second means coupled to the first means for moving between first and second positions for actuating the first means to compress the cup-shaped member with the second means moved from the first to the second position.