Abstract: An apparatus for blocking the flow of fluid through a conduit such as a sewer inlet or the like is provided. The flow-blocking apparatus includes an expandable bladder, a compressed-gas source for supplying compressed gas to effect expansion of the bladder, and a handle device for supporting the compressed-gas source while the bladder is positioned in the conduit to be blocked. The handle device is configured to permit an operator to actuate the flow of compressed gas to the bladder while continuing to support the compressed-gas source. The handle device preferably includes a base portion, a movable portion pivotable relative to the base portion and an actuating member movable in response to pivoting of the movable piston for controlling the flow of compressed gas from the compressed-gas source to the bladder. The apparatus also includes a burst protection plate which deflects compressed gas escaping from the bladder to thereby prevent any injury to an operator.