Yes my friends today we are getting down in the gutter filthy and talking some sewer line smack. The sewer line that links a house to the main sewer service is typically buried underground and quietly doers its thing ridding your home of the nasty necessity of life. We all take it fro granted; there it lies out of sight and nearly always out of mind. Seriously, who wants to think about sewage?
Many people that are looking at buying an older home do think about getting the sewer line inspected and this of course is a wise idea. After all a sewer scope is often price well under $150. Sometimes complicated setups in the home connection may cause the price to go up a bit, but 90% of scope jobs are quick and reasonably priced.
Often however people only think to do it on really old houses. The logic is sound, and old sewer line laid in 1945 is indeed more likely to have issues than one laid ten years ago, right? Well, maybe. Sometimes the underground work on new home developments is rushed, sometimes back fill is not exactly proper and sometimes a big old fast growing tree can disrupt an otherwise sound sewer install.
The primary concern is a blockage or serious leak in the line. A blockage often is the result of plant root intrusion. The roots can break into the line through a seam in the pipe fitting. often that is caused by a large root pushing on the pipe or normal decades of ground settling. Below is a video from a sewer line company on you tube that shows a root intrusion on the sewer cam. I am not affiliated with this firm and this video was taken in another area of the country, but still provides a good idea of how the sewer line camera inspections look. This shows a severe intrusion and you can see how this might lead to a backup. It is also important to note that one should never flush any solid objects other than toilet tissue and what comes out of our bodies as those "foreign" objects will log jam against even much smaller root intrusions than this one. Foreign objects includes feminine hygiene products which are the number one cause of self inflicted sewer backs ups.
Another issue is what plumbers refer to as a "belly". This is where do to settling over time or a less than adequate install job the sewer pipe has a dip between the house and the main line in the street. Understand that the vast majority of sewer lines are gravity based. The house sits up high on a foundation and there is a slope from the house to the main buried in the street. When you flush the toilet or run water in the bath or sink that water runs down a pipe and picks up speed as it heads down towards the main line. A belly in the line means that the "water" dips and then has to rise back up. Sewer line slops are often very gentle slope. A standard 4 inch line should have a minimum slope of about 1/8" drop for every 12" of length. A belly in the line at the minimum slope can cause enough of a slowdown to create problems. Sewer problems are not pleasant.
A belly in the line is not always a deal killing event and in some cases the combination of pipe size and actual slope may be enough that it is not a concern. This is best left to the pros who understand the basic mechanics and physic of gravity sewer lines.
I would recommend that sellers do a sewer scope test in advance so they know going in whether there is an issue to address. Of course here in Washington State and probably every other state, once the seller is aware of a problem they have to disclose it, so there is that issue. I personally would rather know what potential issues I may have as a seller before a list my home.
Buyers should always consider having the sewer line checked out, even on newer homes because installers can make mistakes in the installation that can slip by the government inspections. Spending an extra $125-$150 on your inspection to get a potentially $2000-$10,000 dollar repair item checked before you buy is sound advice.