In the course of performing home inspections at older homes, along with knob and tube wiring, one of the most common issues that I find involves aged metal plumbing pipes. The old pipes commonly found in the Bellingham area and Whatcom County include cast iron, galvanized steel (drain and supply pipes) and even lead pipe at toilet drains.
Some clients wonder why the old pipes would even be considered a problem. The answer to that, based on when the materials were commonly installed, is that most old metal pipes are at, or beyond, estimated design life of 50 or so years. When supply pipes are galvanized steel, the piping is usually heavily rusted and water at fixtures is brownish in color and rusty.
Another problem with old metal piping, not unlike the case with knob and tube wiring, is that the piping may be run in places that are not readily apparent -- insides walls and under/behind finished surfaces. Therefore, when there are old plumbing pipes, it almost always makes sense to have a plumber go through the system and make repairs or, at the least, issue an opinion on the materials.
In an effort to better explain the problems typically found with old metal piping, I prepared this client video.