Nicolette Forbes

By: Nicolette Forbes on May 20th, 2022

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What Is a Main Sewer Line?

Plumbing | Drains

Your plumbing system can be a complicated place. Some different parts and names can be hard to keep up with which can be frustrating or confusing. One of the most important parts of your plumbing system is the main line, also known as the sewer line. 

We here at Monkey Wrench Plumbing have helped thousands of customers since 2007 with more than just their plumbing problems. We’re passionate about teaching people about their home’s plumbing and help them understand the cause of their plumbing issues. 

In this article, we’ll go through: 

  • What is a main line
  • What causes blockages in a main line
  • How to address the clogged lines
  • How much it will cost to repair or replace

Let’s get started!

What is a Main Sewer Line?

The main line, also known as a sewer line or a main sewer line, is the pipe that goes from your home to the city connection or the septic tank. Everything that goes down your shower, sink, garbage disposal, and toilet runs through this pipe. A main line is often referred to like to as a highway “sewer highway," with the smaller drains serving as the connecting roads. 

The line exits your home and cuts through your yard. From here, the line meets the city sewer system or your septic tank, if you have one. If this line gets clogged, you can count on the fixtures in your home being affected as well. When this happens, you've got a major plumbing problem on your hands. 

Main lines are typically four to six inches in diameter and sloped downwards to promote the flow of debris or waste away from your home and into your city’s sewer. 

A main sewer line exposed

So how can you tell that your main line is clogged?

Hints Your Main Line Is Clogged

Just like the drains in your home, the main sewer line can get clogged. There are a few ways to tell if your main line is clogged.

  1. Back-ups in Your Home

If you are experiencing a backup or are seeing sewage come out of the lowest part of your home, then you probably have a main line issue. The lowest part of your home is typically your toilet, tub, or a stand-up shower.

2. Loud Noises

Yes, the title is a reference to the movie “Anchorman” starring Will Ferrel, but it’s quite relevant to the next symptom of a clogged main or sewer line. If you flush a toilet or use water and you hear gurgling in a different area of the home, there could be a main line problem. Gurgling is caused when something is preventing water or air from flowing through your drains. As the water slowly travels through your drains, air bubbles begin to form and create a gurgling sound.

Whether it's your sink, toilet or shower, even floor drains all can make that gurgling sound.

      3. Sewage Smell

Another key sign that there is a blockage in your main sewer line is the smell. If you begin to smell sewage in your home, there is a high likelihood that there is a break in your main line. Some of the key reasons why you would experience a break in your main line are due to: 

  • Cleaning Frequently
  • Earthquakes
  • Parking Over Lines
  • Old Age

Check out this article for a more in depth look at why you could be smelling sewage in your home.

If you are experiencing any of these problems, we recommend that you call a plumber to come help.

Having a Clogged Main Line

So having a clogged sewer line sounds terrible right? But how does it get that way? Well, many things cause the main line to back up.

  • Debris

When you dump a lot of unnecessary things down your drains, it can cause a blockage in your main or sewer line. Some common items that cause a clogged main line include feminine products, baby wipes, large chunks of food, oil, and other large quantities of debris.

  • Buildup 

Over time, sludge will begin to accumulate in your pipes due to overuse or what we like to call buildup, which is caused by food, hygiene products, cleaning products, and more. This buildup can eventually grow large enough to cause a blockage in your main sewer line.

  • Type of Pipe

The type of material the pipes in your plumbing system are made of can also cause clogging issues for your plumbing system. Cast iron pipes tend to corrode over time which will ultimately cause a blockage in your main line. ABS (or acrylonitrile-butadiene-styrene) pipes are typically used on newly made homes but may need hydro-jetting to prolong their lifespan.

ABS piping for a main sewer line

While hydro-jetting can often help clear blockages, what you put down your drains could shorten the lifespan of your plumbing. Putting drain cleaners down your drains will start to deteriorate your drains over time and eventually will start to hurt your plumbing more than help. Check out this article on the effects drain cleaners can have on your plumbing system. For example, if you throw everything but the kitchen sink into your drains, then your plumbing system will not last very long no matter the material of the pipes.

Closing Out The Main Lines

To recap, we spoke about what a main line is, along with hints that your main line is clogged or is experiencing a blockage, what to do when a main line is having a blockage, and how much it’s going to cost to fix or replace the pipes. Understanding your plumbing system can be a complicated process but we here at Monkey Wrench Plumbing are dedicated to not only fixing your plumbing problems but also helping you better understand your home’s plumbing.

Read the articles below to understand what to do if your sewer line bursts, and what's to be done if your sewer line bursts. 

Pipe Repair: Pipe Bursting

Three Ways To Fix A Broken Sewer Line

While it isn’t uncommon for pipes to get clogged, if you continue to experience blockages, that could be a sign that there's a bigger problem with your drains. If you're experiencing frequent stoppages, calling a plumber to clear the line and perform a camera inspection can help you identify any issues and what solutions are available. 

We here at Monkey Wrench Plumbing want to make sure that you are prepared for anything. If you have seen any of the signs of a local or mainline stoppage, or are experiencing any other issues with your plumbing, call us at (310) 853-8690 or continue your research at our Learning Center.