There is evidence suggesting that indoor plumbing began in 8000 BC, when households in Scotland used basic plumbing to carry water to a nearby creek. Plumbing continued to advance through the ancient era, but was neglected in Europe until the 19th century, which was when large systems were developed.
The earliest evidence of indoor plumbing comes from Scotland in 8000 BC, where water was used to flush waste from indoor troughs to a nearby creek. In 4000 BC, perforated bricks were use to drain water from homes in Iraq to pits that lay beneath them. By 3000 BC, people living in Crete were using rudimentary toilet systems, which required servants to pour water that would flush waste away.
During the middle ages, parts of Mesoamerica used basic flushing systems. However, many parts of Europe saw a decline in the advancement of indoor plumbing, leading to unsanitary conditions. This began to change in the 19th century when public health officials linked the spread of disease with unsanitary conditions.
This led to the advancement of underground sewage systems, which required indoor plumbing. Initially, lead piping was used in many parts of the world, and galvanized iron in the U.S. Eventually, most households relied on copper piping for their indoor plumbing systems.