Homes built prior to 1970 have sewer lines composed of either orangeburg pipe or lead (black) pipe. More modern homes use PVC.
According to Wikipedia “Orangeburg pipe (also known as “fiber conduit”, “bituminous fiber pipe” or “Bermico”) is bitumenized fiber pipe made from layers of wood pulp and pitch pressed together. It was used from the 1860s through the 1970s, when it was replaced by PVC pipe for water delivery and ABS pipe for drain-waste-vent (DWV) applications. The name comes from Orangeburg, New York, the town in which most Orangeburg pipe was manufactured. It was manufactured largely by the Fiber Conduit Company, which changed its name to the Orangeburg Manufacturing Company in 1948.”
A quick translation: Orangeburg is heavy cardboard soaked in oil. It collapses over time, and has a lifespan of about 40 years. If you are considering buying an older home, and the sewer line hasn’t been replaced, then you are looking at $5-10,000 to change out the orangeburg. This price will vary depending on the length and location of your sewer line.
Symptoms of a collapsed line are toilet back ups and slow tub draining. The for sure notice your line is gone is when the toilet is flushed, a geyser of water blows back up at you.
The lead pipes collapse as well, and will show the same symptoms when gone.
Many older homes also have galvanized steel for the plumbing. By comparison, modern homes use copper or PVC. Copper came into common use in the 70’s. The reason for the change out is that galvanized pipes act as a magnet and attract minerals in the water which adhere to the lining of the pipe. Over time, the minerals will build up, slowly sealing off the pipes until the water can’t pass through them anymore. They will have to be cut out and replaced, which can be quite expensive depending on the location of the pipes.
When looking to buy an older home, always ask the type of plumbing in the house, if it has been updated, and if so – when. If not, you need to factor in the cost of replacing the plumbing when factoring an offer.