Abstract: An expansible, resilient receptacle positionable about a standpipe installed for the relief of subsurface water pressure occasioned specifically by sewer backup. The receptacle surrounds the standpipe and communicates with the inner portion thereof through strategically located openings in the walls of the standpipe. The water introduced to the receptacle bulges its walls and urges a watertight engagement between the walls and floor about the base of the standpipe. The seal contains any water leaking upwardly around the base of the standpipe and prevents the floor from failing. In the event the excessive subsurface water pressure is encountered, the water is permitted to escape into the room to avoid possible rupture of the floor surface. The water is releaseable from the receptacle when the subsurface pressure diminishes.