How to Find the Main Sewer Line in Your House

Sewer line, drain line, branch line, secondary lines… there’s a lot going on throughout and underneath your house to keep the home’s plumbing and underground utilities running smoothly. And, with all of the different moving parts, especially when it comes to the sewer systems and drainage systems, it can be difficult to understand what everything is, where a particular problem may be occurring and what exactly needs to be looked at or fixed.

While there are a lot of different plumbing lines in your home, they all lead to one place: the main sewer line. The main sewer line either connects to your home’s septic tank system, or a sewer main/municipal system that is maintained by the city. Knowing exactly where your home’s main sewer line is can be useful when you’re experiencing any sort of issue involving clogs, backups, leaks or breaks so you troubleshoot yourself, or so that you know when to call in a professional plumber to get the help you need.

Ways to Find Your Main Sewer Line

First thing’s first, you will have to hunt a little for the main sewer line. One of the access points to the main sewer line can be found through the sewer cleanout that is inside of the home or outside in the yard. Work through the following steps to find its location:

• Start inside. Look for the indoor sewer cleanout pipe that can typically be found in the garage, basement or crawl space. The sewer pipe is generally about 3-4 inches in diameter and has a cap on the top that allows you to access the sewer line in order to remove blockages.
• Can’t find it inside? Try outside. Many homes have sewer cleanouts that are located outdoors, usually near the foundation of the home or near the street where the sewer line meets the municipal sewer main. An outdoor sewer cleanout can look the same as its indoor counterpart and stick out of the ground making them easy to find.
• Having trouble finding it outside? The sewer cleanout cap could be obstructed by landscaping, overgrown weeds or anything else close to the home. Or, the sewer cleanout could also be buried and therefore much closer to the ground. It could also be concealed in a metal box. Try looking on the side of the house near the foundation and close to the main floor bathroom.
• Still can’t find your sewer line? If you have the contact information for the previous owner, you can try asking them. Or, check with the city maintenance department or City Hall to see if they are able to look at a sewage or property map to determine where your sewer cleanout is located. If you have a septic tank, you can also find the tank and work backwards from there. And, as always, the best option may be to contact a professional plumber to locate the main sewer line for you.

Next Steps

So you’ve found the main sewer line in your house, now what? Because the sewer line will be buried underground, it’s time for a professional to step in. If you suspect a break in the main line and you don’t have experience with plumbing, digging things up yourself will most likely make the situation worse. Even if you can see a clog from the sewer cleanout, do not attempt to clean it yourself. Instead, call a plumber to assess the situation and determine what steps you will need to take next.