Like clogged arteries - many thanks for such great info presented in such an accessible, friendly style. New homeowner with interest in becoming an inspector here - subscribed!
Only rule- if it has galvanized pipes, regardless of age. Get rid of it. Lived in Houston where many homes even from the late 70s used galvanized. It all sucks. Rust flakes off inside and clogs everything. Replaced it in our 1977 home with pex and was astonished by the pressure afterwards.