Abstract: Apparatus is disclosed for impregnating a wall or the like with damp-proofing fluid. The apparatus comprises a conduit through which the fluid passes and carrying a sealing element designed to seal against the wall automatically under the pressure of the damp-proof fluid. Generally the sealing element comprises a grommet which is deformed into sealing contact with the wall, the deformation being effected either by the direct action of the damp-proofing fluid on the grommet or through an intermediate member such as a piston in a cylinder carried on the conduit.