Rod plug caps

A plug for leaky tubes of a heat exchanger, said leaky tubes having ends with outside surfaces and diameters, comprising:

• (a) a frustrum shaped tapered hollow plug having a top, a length, and a diameter at the top, said diameter of said top being the widest of said plug;
• (b) a plug nut formed on said top of said plug, said plug nut and said plug being formed from one homogeneous piece of material;
• (c) a threaded rod disposed longitudinally through the leaky tube, said threaded rod passing through said plug and said plug nut and then through a gasket washer and a rod nut;
• and
• (d) an "O"-ring disposed inside the leaky tube around said plug, said plug diameter at the top being less than the outside diameter of the end of the tube so that nothing extends or protrudes past the outside surface of the end of the tube and therefore, allowing the stopped tubes to be disposed in close proximity to each other and to the other tubes of the heat exchanger.