Abstract: A flow-through pipe plug for conduits which permits controlled blockage of fluid flow in a conduit in which the plug is installed, the plug having a rigid cylindrical core on which are secured an outer bladder and an inner bladder, the bladders and core forming chambers between the bladders and the core, the core having pressurizable fluid supply pipes to the chambers with hose connectors for connecting the supply pipes to an auxiliary component for independent pressurization of the chambers and expansion of the respective bladders with the outer bladder expanding to the inner wall of the conduit in which it is installed and the inner bladder expanding to block passage through the core.