Galvanized water supply pipes were the most common method of providing water in homes from the early 1900’s until the early 1950’s. While there are a lot of factors that can contribute to how long these pipes will last, it is generally recognized that these pipes have a life expectancy of 40-50 years. By these any galvanized piping installed before 1950 is past its expected life.
During this same time period, the same type of piping was used for drains as well. One should conclude that these pipes are also at the end of their expected life. When I find them I usually recommend replacement of both supply pipes and drain pipes for cost efficiency. Once you have gone to the trouble of getting the plumber there, why not have them replace both.
Here is a picture of a drain line that has reached the end of its expected life. The stalactites of corrosion are where the pipe is leaking and re-sealing itself through a process called autogenic healing. This process will go on until the pipe can no longer seal itself, at which time the pipe will leak all the time.
When your pipes look this bad on the outside, it is a pretty safe bet they look much worse on the inside.
Charles Buell, Seattle Home Inspector
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