Fastener

A fastener for securing an attachment to an inner surface of a wall confining a fluid, wherein the attachment has an internally-threaded aperture formed therein to receive an externally-threaded boss passing through an aperture in the wall registered with the aperture and the attachment, comprising:

• (a) a hardened washer having a central aperture formed therethrough and threads formed in an outer peripheral surface thereof, said washer aperture being defined, along its full axial length as it extends through an axial dimension of said hardened washer, by a conical surface wherein said aperture, when said hardened washer is in engagement with the outer surface of the fluid-confining wall, has a larger diameter at an end of said aperture more closely proximate the outer surface of the fluid-confining wall, and said washer aperture being registrable with the aperture in the fluid-confining wall when said washer is brought into engagement with an outer surface of the wall;
• (b) a bolt including the externally threaded boss and a head at one end of said boss having a diameter larger than said aperture formed in said hardened washer, said boss of said bolt being able to be passed through said aperture in said hardened washer and the aperture in the liquid-confining wall and threaded into the internally-threaded aperture formed in the attachment when the hardened washer is in engagement with the outer surface of the fluid-confining wall to tighten the attachment securely against the inner surface of the fluid-confining wall;
• and
• (c) a cap having a cylindrical chamber formed therewithin, said chamber having a defining wall, internally threaded compatibly with threads formed in said outer peripheral surface of said hardened washer, wherein said cap is able to be threaded tightly against the outer surface of the fluid-confining wall when the attachment is tightly secured to the inner surface of the fluid-confining wall wherein said washer aperture defines, when said boss of said bolt is passed therethrough, a widening annular space between said conical surface defining said aperture and said boss of said bolt, and further comprising an annular elastomeric seal receivable within said space, wherein as said bolt is tightened down, said elastomeric seal is compressed to more efficiently seal and interface between said hardened washer and the fluid-confining wall.