What Causes Bellies in Sewer Lines
One of the most frustrating yet common emergency plumbing situations that occur in a home is a main sewer line blockage. One of the reasons that it is so frustrating is that when your main backs up, you cannot use any drains in the house. Even washing your hands in the kitchen sink can cause a toilet to overflow all over your bathroom floor.
The other reason for the high frustration factor is that you call the plumber out and have him clear the line, often to have the same problem pop up in a year, or six months, or maybe even a month. The reason that this happens is because the most common cause of main sewer line back ups is tree roots.
Roots grow into the small gaps where the sections of pipes meet and get into the sewer line. There they find “nutrient rich” water that helps them to grow. As they grow, they open the gap to let more roots in, and in some cases even crush the pipe. The plumber comes along and cuts the roots, but, in essence all he is doing is pruning them. That means they only come back faster and stronger. By cutting out the roots, he is actually helping them to grow!
So what does this have to do with having a “belly” in your sewer line? A belly usually occurs when two pieces of pipe are separated enough by root intrusion that the back end of one of the pieces of pipe is allowed to sink. This is compounded by the fact that the ground around this separation is often saturated with sewer water. That section of pipe sinks enough that it is no longer flowing down hill. At that point, it is said to have reverse grade, or a belly.
This can be bad because bellies will accumulate debris and increase the chances of a backup. Bellies are also a problem because while there are methods to fix root intrusion such as pipe lining or small spot repairs, fixing a belly often involves the excavation of at least 10 feet or more of the pipe.
The best thing that you can do to avoid a belly, and the increased cost of fixing one, is to address sewer line backups more aggressively, earlier on. If your sewer line is clogged, find out why, and get it repaired right away. After all, this is your plumbing, and your house does not “work” without it!
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I need some clarification, if you will. I appreciate the article, and have a couple of questions.
From your article, “So what does this have to do with having a “belly” in your sewer line? A belly usually occurs when two pieces of pipe are separated enough by root intrusion that the back end of one of the pieces of pipe is allowed to sink. This is compounded by the fact that the ground around this separation is often saturated with sewer water. That section of pipe sinks enough that it is no longer flowing down hill. At that point, it is said to have reverse grade, or a belly.
1) When you write “the back end of one of the pieces”, I think this refers to the end that is not separated – is this correct?
2) Any idea of the ramifications of that end sinking – is the soil below it overly compacted, will the sinking pose a problem for the slab above it?
3) What kind of problem would be caused by having the ground around the separation saturated with sewer water?
Thanks for your consideration,
Charlie Koonce