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Sewer Line Scopes 101

Updated: Oct 25, 2022

We want to make understanding sewer lines easy for everyone. Let’s talk about the plumbing components we review on our sewer scope.

Internal Section

This portion reviews features of the indoor plumbing system within the house. When we arrive on-site for your scope, we will need to find an access point and we take a look at the visible plumbing system of the home. For example, in an unfinished basement it’s very easy to see the exposed plumbing lines of the first floor running along the subfloor. We will note any issues we find such as dripping along the lines or a visible issue with the vent stack. The internal line also includes the part of the sewer line we view before it leads to the outside section of the home. This section of line is within the structure’s foundation walls.

Transition Point

The transition point is where the internal section of the line ends and the external section of the mainline begins. This section is important to check for leaks and root intrusion as it can cause foundation issues if not properly aligned.


The mainline is typically the longest section of the sewer line system. This section carries the wastewater from the internal lines and transition point to the city sewer system or septic tank. The mainline is typically made of clay piping or PVC. We review the grading of the line to ensure the wastewater is being moved away from the home and not backing up in the line. In older lines, this is where roots from trees and other landscaping can typically be found.

Ending Point

This is where the wastewater enters the next stage of the freshwater cycle. The mainline will lead to a septic tank or city tap connection. This connection may be under the street for a city tap or on the property underground for a septic tank. Either connection is important to check for leaks. If the city tap is not properly connected, waste water could be entering the ground underneath the street and cause major issues long term. If a septic connection is not properly working, there could be wet areas in the yard leading to a biologically hazardous situation in the future.

Problems found within any of these sections can be expensive for homeowners. Leaks found in the internal section and transition point can lead to costly foundation repairs if not fixed as soon as possible. Mainline repairs may require digging in the yard and street to resolve damage or breaks in the line. A sewer scope can find issues before they get too costly, so if you have issues with any section of the line and want a closer look, we’re happy to help!

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