How do I know if my Costa Mesa home's galvanized pipes are done?

The signs arrive as a set: rusty or yellow first draw after the water sits, pressure that fades when a second fixture opens, pinholes appearing in different rooms within a year or two, and visible thread rust at exposed runs in the garage or attic. One sign can be a fixture problem. Three together describe a system at the end of its material life, which in Costa Mesa's 1950s tracts is the expected finding. The confirmation is a pressure read and a look at the exposed runs, both cheap, both decisive.