Main line vs Drain Line – What’s the Difference?

August 22, 2023

You may have heard of our mainline plumbing coupons, but did you know it’s actually for a specific line in the home? That’s right, it’s for your home's sewer line.

Residential sewer lines tend to back up when damage or roots are present. These backups are different from a backed up toilet, sink, or drain. When your fixtures are backed up, it’s typically an issue with your main drain (or main stack).

As homes age, the main line can become damaged and roots from the surrounding trees and vegetation can enter causing blockages. These can cause serious problems which require professional attention.

If you want to better understand the differences between the mainline and drain line, keep reading.

What is a main line?

Simply put, your mainline is your sewer line. And all your drains connect to your main line. Your main line is also the line that goes from your house to the city connection or your septic tank. Before leaving your home, all of your drains dump into your mainline. When your mainline backs up, it is important to know where your clean-out is located.

All homes should have a clean-out for the mainline. It’s usually inside your home in the lowest portion of the home or outside of your house. If you live in an older home and don’t have a cleanout, a plumber will most likely pull a toilet and run the line through there; although the extra work will add more cost. It is also possible to have a cleanout installed in your home to ensure that there is easy access for any potential future problems.

When you are having an issue with your mainline, you may also be experiencing other plumbing issues in your home. When you see a backup in the lowest part of your home is usually includes sewage and you can assume you have an issue with your main line. Your local plumber should be able to help you remove blockages and help resolve backups in your main line. 


If you’re having an issue with your mainline or a drain line, there are a few things to look out for. First, find where the backup is located. If it is in the lowest part of your home, there is a chance it could be the mainline. If there is sewage coming out, it most likely is. 

If you hear gurgling in a different area of the home when using any water, there could be a mainline issue as well.

What is a drain line?

You have many drain lines in your home. Because all drain lines eventually connect to your main line, if you have an issue with your main line you will experience issues with many drains. That’s why backups happen.

If you have issues with a specific sink, shower, or toilet drain you most likely will be able to use the plumbing everywhere else in the home because they are not connected. If certain drains are connected, both may act troublesome. Bathrooms tend to have multiple drain issues stemming from one major problem. 

The easiest way to know if you are just experiencing an issue with a drain line is to check other parts of the house to see if the drains are working. As mentioned above, oftentimes bathroom lines will connect and even kitchen sink drains can connect with dishwashers. While a clog can affect the connected drains, if the whole house isn’t experiencing an issue, it is likely you just have an issue with a single drain. 

The plumbers at Hamilton are equipped with the tools and advanced equipment to help solve drain line issues and provide drain repair.

Why should I know the difference?

Knowing the difference between the mainline and the drain line is important because they are two different plumbing issues and repairs are priced differently. The equipment and fixes for these lines are different as well. 

The mainline can be inspected with a camera to identify the problem at hand but a drain line cannot. Sometimes, a severely damaged mainline will require a crew to dig up all or part of your yard to get to the mainline sewer line for repairs. In these instances, partial sewer line replacement may be necessary. 

In the Kansas City area, main lines can be damaged from age which causes cracks. Along with potential cracks or growing roots, pipes can become blocked by debris, grease deposits, offset pipes, or a low-sagging area. The experts at Hamilton are trained to help you with any potential issues and have the tools to clear away these blockages and ensure any blockage doesn’t turn into a bigger problem. 

To contrast the issues you may be experiencing with a main line, a regular drain line would be fixed by a plumber who will be working inside the home the entire time. Often, these pipes are too narrow to send a camera all the way through. Not all issues with a drain line have clear causes and some may require a bit more investigation. A trained plumber can help you quickly address issues and uncover hidden problems. 

Regardless of the type of issue you are having, Hamilton can help. Schedule a service with our team today if you discover drain issues in your home.

If you are seeing any of those symptoms for your mainline, call us to take advantage of our $99 mainline opening special. It comes with a free camera inspection. If you are having issues with your main line or any of your drain lines, schedule a service or give us a call at (913) 227-4943 so we can help or answer any questions you have.

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Last Updated: July 10, 2024