Updated: Oct 25, 2022
If your house was built before the 1980’s, there’s a good chance you have a clay sewer line connecting your house’s plumbing to the city sewer system or septic tank. Cast iron, plastic (PVC), Orangeburg, and concrete pipes were also widely used, but the most popular type of sewer line material was clay before PVC became the most common material for newly built homes.
The earliest known use of clay for piping dates back to 4000 B.C. It’s a versatile construction material and is still used in plumbing projects today. Clay pipes are made from shale and clay that is compressed and heated in kilns to create the final product. These pipes are chemically inert meaning they do not react to wastewater and chemicals that may come in contact with the pipe. Of course in home usage, chemicals should never be flushed or put down drains as they could react with wastewater or be harmful to a septic tank or city sewer system.
While the clay pipes are very strong and are made to withstand thousands of pounds of pressure, there are some disadvantages of this pipe. The clay pipes are very heavy and can be difficult to transport and install. Clay pipes are typically smaller in length and then connected together to create a longer line. Rubber joints, hot-pour compounds, and cement were used to connect clay pipes. Over time, these joint connectors can break down and cause the line to leak. Roots from nearby trees, shrubs, and other vegetation can find their way into the sewer line and create restricted flow in the line through these joints. Regularly cleaning the line can help keep these roots from causing damage or backing up the line.
Larger leaks over time can cause the soil around the line to become displaced. When too much soil is moved around these joints, offsets in the joints can occur and the flow can be cut off to the ending point of the sewer line.
Having a smaller pipe length may actually be an advantage in cases when repairs are needed, though. Sometimes just that section of the sewer line can be repaired and a full line replacement isn’t necessary. Clay sewer lines are not widely installed into new homes now, but clay pipes have stood the test of time for use in various projects. If you have a clay sewer line, it doesn’t automatically mean it needs to be replaced, it may just need regular maintenance and cleanings to keep the roots out of it. We’re always happy to view these lines and save homeowners money in costly repairs!
Griffin, J. (2020). Clay Pipe Gets Better with Age: In a World of Plastics, Clay Pipe Still Stands Out. Underground Construction, 75(8), 14–16.
Comerford, S. (2022). Sewer Line Root Intrusion: Prevention and Removal. Underground Construction, 77(1), 42–43.
Evans, J. & Spence, M. (1985). The Evolution of Jointing Vitrified Clay Pipe. Advances in Underground Pipeline Engineering. Pipeline Division, ASCE / Madison, WI / August 27-29, 1985.