What Causes a Broken Sewer Line?

Why is it important to know what causes a broken sewer line? Every pipe and plumbing fixture in your home connects to the most important piece of plumbing — the main sewer line. Here’s the good news: not all breaks warrant an immediate repair or replacement.

Broken Sewer Line Due To Pipe Settlement

One of the most common problems causing a broken sewer line is ground settlement. When the ground around the pipe has settled, the pipe can sink and create a downhill slope in the wrong direction. This is called back-pitch.

Waste and water that should flow downward, away from your home, will stop in the sunken area or flow back toward your home. Over time, waste will accumulate in the settled pipe causing a blockage. The only solution to a back-pitched pipe is to dig and repair the slope of the broken sewer line. 

Broken sewer line - backpitch vs Belly vs Channeling
This diagram shows a positive slope away from the home (at top) vs two versions of a back-pitched pipe, which slope down and eventually cause the sewer line break.

Improper Sewer Line Installation

A sewer line works based on the principle of gravity. The water and waste need to run downhill. Improper installation can lead to settling and back-pitched pipes. With a proper installation, a broken sewer line caused by a low area should be unlikely.

Most plumbing codes require sewers to have a downward slope of 1/4-inch per foot — from the house to the city’s main sewer line in the street. Your city’s plumbing code may require the plumber to place gravel underneath the entire run of pipe. It’s a good standard practice regardless.

If the main sewer line is not installed with proper fall (the amount of downward slope) or the proper support, the pipes will eventually settle and break.

Broken sewer line - installing new sewer pipes
The repair of a broken sewer line can be expensive and time-consuming. Having the right expertise and equipment are essential.

Tree Roots in Sewer Line

Another common cause of a sewer line break or damage is tree roots. Tree roots grow toward sources of water, making them naturally attracted to the sewer lines.

Once the roots make contact with the sewer pipe, they will begin to wrap around and break into the pipes. Over time, the pipes will become weakened and lead to cracks. Roots will grow through the cracks and continue growing inside the pipes, eventually leading to clogs. 

A more experienced drain cleaner may use a hydro jet to clear out roots. But over time, you may need to hire a plumber with the proper excavation experience and equipment to dig up and replace the sewer line in compromised areas.

A hydro jet is commonly used by drain technicians to clean and clear a sewer line of tree roots and other stubborn debris.

A camera inspection can locate exactly where the breaks are. It will also indicate if a spot repair or full sewer line replacement is recommended. Your plumber shouldn’t have a problem if you’d like to take a look for yourself.

A camera line inspection allows the drain technician to see any problems inside the broken sewer line.

Once the tree roots break into your sewer line, they cause these two common problems:

  1. The damaged portion of pipe allows sewage to leak out into your yard, causing issues such as standing water, spongy grass, and an unpleasant smell.
  2. The tree roots can continue to grow up into the pipe as they absorb water, causing a partial or complete blockage of your sewer line that affects drainage inside your home and may even lead to a sewage backup. 
sewer repair tree roots
Tree roots are a major cause of sewer line breaks and lead to problems like standing water. It can aso cause foul odors in your yard or even backed up into your home.

Sewer Pipe Deterioration

Many people turn to chemical treatments when they have a backed up drain. Frequent treatments with chemicals will inevitably cause corrosion. If your water is discolored, there is low water pressure, or you are finding signs of leaks, you may have failing pipes due to pipe corrosion.

Chemical treatments are simply too harsh in our opinion. We do not recommend their use because they (1) often don’t work as well, (2) can be harmful to your health, and (3) cause corrosion which deteriorates and weakens your pipes. This leads to worse problems down the road.

A broken sewer pipe due to deterioration from use of chemical cleaners.

How to Protect Your Sewer Lines

Not all sewer damage can be prevented but there are a few things you can do to help protect the life of your main sewer line

  1. A licensed plumber can provide a sewer camera inspection of your drains. The camera will show exactly where any breaks or blocks are located so that you can be proactive in preventing further damage.
  2. Be on the lookout for trees along your sewer path. If a tree is damaging your sewer line, you should remove the tree before the sewer problem worsens. 
  3. And remember to always use your sewer line properly. Only dispose of human waste and toilet paper in the sewer lines. Any other materials that enter the system can cause blockages.


Unfortunately, until you have a problem, a sewer line is often the most neglected and forgotten piece of plumbing in your home. The consequences of that are incredibly time-consuming, frustrating, and expensive.

The improper use or installation of sewer lines, coupled with natural forces you can’t control, means your main sewer line takes a serious beating. And while no sewer lasts forever,

Call 1-Tom-Plumber

1-Tom-Plumber has an entire team of specialists who focus solely on drain cleaning, drain clearing, and sewer line excavation and repair. So don’t hesitate to contact or call us at 1-866-758-6237. We will immediately respond to your emergency plumbing, drain cleaning and drain clearing, or water damage problems.

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