Complex sentence: In the twentieth century, the first plumbing pipes were made from galvanized steel water pipes, but users experienced problems with the internal build-up of rust which reduced water volume, but these were replaced by copper pipes in the late 1960s.
Split into simpler sentences: In the twentieth century, the first plumbing pipes were made from galvanized steel water pipes. As users experienced problems with the internal build-up of rust which reduced water volume, these were replaced by copper pipes in the late 1960s.