The older your house, the more likely you are to have a sewer line or main water line problem. If your house was built before the 1970s, it probably will have pipes made of cast iron or clay. The fittings that connect cast iron pipes will loosen over time due to soil movement. The pipes are also susceptible to breakage due to the erosion of the surrounding soil.
The pipes and fittings can corrode from within as well.
Clay or ceramic pipes tend to attract tree roots more frequently. Older homes often have more plumbing issues simply because of cast iron and clay pipes used in underground water and sewer lines.
Houses built from the 70s onward generally have PVC piping for the sewer line (and PVC is usually used as the other piping in the plumbing network). These heavy plastic pipes do not corrode like clay and cast iron pipes. Unfortunately, PVC pipes are not invincible. Any pipe can fail as a result of soil movement or the invasion of tree roots.
Tree roots are a common cause of main water line and sewer line breaks, clogs or blocks.
Roots seek moisture and tend to grow into underground water and sewer pipes. Unfortunately, water and sewer lines are not always installed correctly and water will leak from the joints of the piping. When that happens, the thirsty tree roots grow towards the leaking water, eventually finding their way to the pipe, and then inside it. Before long, you have a restriction in your pipeline. Tree roots are a nuisance when it comes to water and sewer line problems. Keep this in mind if you have large trees in your yard and are having sewer and water problems.
Clogging is a problem primarily with sewer lines. They may get filled with grease and hair, or plastic and paper products that do not degrade.
Hot fat, oil, and grease go down the sink pretty easily. You wouldn’t think it’s a problem in liquid form but once they are in your drainage system, fat, oil, and grease cool down and turn to a solid very quickly. When it sits and collects in certain parts of your sewer line, it will collect other solids and build up until a nearly total blockage occurs. If your dirty water can’t get through the pipes, it will go somewhere inconvenient, perhaps back into your house.