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What Is a Belly in a Sewer Pipe?


Sewer line bellies are a common problem that can create aggravating sewer pipe problems for property owners. A sag in a sewer pipe will eventually lead to standing water and sediment collecting in the middle of the line, which in turn can lead to erosion, blockages, and a major backup for the business owner.

Sewer line bellies are sags or low spots in sewer lines. A normal sewer lateral (seen below) has a slope that uses gravity to help regulate the flow. A bellied sewer line interferes with the normal flow of waste water through the pipe, leading to backups and other problems because the water and sediment collects in the belly.

What Causes Sewer Bellies?

Poor planning and bad installations are often the root cause of sewer line bellies, as proper bedding compactiongood materials and correct slope are the most important factors needed to prevent the problem. However, natural occurrences like major tree roots, earthquakes, sun or heat, rain, and even cold weather fluctuations can lead to the shifts in the soil that eventually cause bellies.

To prevent bellies, the first step is to call for a consultation from a specialist like Ideal Services NW or other Commercial Plumber. If the correct material (larger grade gravel and sand) is not used under the pipe, then it may eventually settle lower into the ground in some sections and a belly will form.

A sewer line must also have the correct slope in order to use gravity to its advantage when moving waste away from the home or building. A trenchless professional will use the best tools of the trade (such as video cameras and locator wands) to ensure proper slope in a plumbing installation thereby preventing excess build-up.

In some cases, unstable ground may cause bellies, too. Even sewer lines that have been installed with the appropriate support in place may sag if the earth below begins to shift.

How Can You Diagnose the Problem?

Sewer pipe bellies should be diagnosed by plumbers using the most accurate video inspecting technology. A professional sewer camera inspection will allow the service technician to push a video camera through the pipe, giving you a close look at the entire sewer lateral and allowing the plumbing team to accurately identify the issue. Even slope issues can be detected at this preliminary stage of the process.

Sewer Belly vs. Channeling

Sometimes a problem may be misdiagnosed as a belly when the real issue is actually sewer channeling. Channeling occurs when the pipe itself begins to buckle in sections due to erosion or a change in the weight on the pipe due to shifting earth. When a pipe buckles like this it can interrupt good flow and create more blockage and build up (see below).


Channeling is a common issue with a type of sewer line called Orangeburg. Orangeburg pipe was used in some jurisdictions between about 1945 and 1972. The problem with this material is that it is primarily made of tar paper, so it had a tendency to buckle as it got older. After about 30 years, flattening and decay could lead to a channel. Fortunately for those of us in the Northern California, Orangeburg was more prominent in the eastern states—while newer developments here used mainly cast iron, clay and (later in the 60’s and 70’s) plastic.

How to Get Rid of Problems with Bellied Sewer Pipes


Each case is different, so there is no magic correction technique when it comes to a belly in your sewer lateral. At Drainjets NW we solve bellied lines with our one of a kind system that you can find out more about here.

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