Water heater foam stop apparatus

The storage tank portion of a water heater has an outwardly projecting threaded pipe coupling fitting and is disposed within a jacket structure that forms an enclosed insulation space around the storage tank, the outer end of the pipe coupling fitting being spaced inwardly apart from a pipe connection opening in the jacket structure. A generally tubular foam stop member having a convexly curved side portion is positioned within the insulation space before the space is filled by an injection process with a liquid foam insulation material. The foam stop member receives the pipe coupling, is axially pressed between the storage tank and the jacket structure, and forms a seal around the pipe coupling fitting and around the jacket structure pipe connection opening. During injection of the liquid foam insulation material into the enclosed insulation space, the foam stop member serves as a relatively small barrier that essentially precludes the liquid foam from escaping outwardly through the jacket structure pipe connection opening or entering the pipe coupling.