Copper water pipes started becoming common in new North American homes starting in the 1930’s, and have remained more or less the go-to ever since. Lead pipes were in use prior to that but have mostly been replaced by now, for obvious reasons. Galvanized steel was also common until the 70’s. Plastic enjoyed a bit of a boom during the 1980’s and 90’s, but copper remains the leader in the present. Copper can be found in both old and new homes, especially homes built within the past 50 years or so.