How to Find Underground Sewer Pipes

Deep under your property are your sewer pipes, which are invisible to all but subterranean creatures. If you have a leak or need to replace these pipes, how can you locate them?

First, you know that every drain in your house — every sink, toilet, shower, or bathtub — drains into a single sewer line. This main line then runs to a municipal sewer system or a septic tank. If you can locate where the main drain exits your property, you're halfway there.

The first option every homeowner should try is to call the city. Most cities maintain maps of the location of underground utilities. Provide your address to see if your city maintains sewer maps.

If that option falls short, start analyzing the exit areas of the pipes in your home. Since all your drain pipes lead to a main sewer pipe, find a toilet or sink line and track it if possible to see where it ties into a larger pipe. The larger pipe should exit your house from the basement or crawl space. That will be the pipe that connects to your main sewer line. Sewer lines are always straight, so this strategy may result in your locating the line.

Try calling 811, the national toll-free number created by Congress to try to prevent damage to underground utilities. Homeowners are required by law in all 50 states to call 811 before digging for any reason, whether to plant a tree, bury water pipes, install a fence, or repair a sewer line. This service will send professional line locators to the site to mark the paths of underground utilities.

Professional plumbers have nifty tools at their disposal: cameras and sensors on the end of long cables that snake through your pipes to identify problems and pipe locations. Sewer cameras are not cheap, and they also take expertise to manage, so if you haven't had luck locating your sewer pipes on your own, it's best to call a professional. Furthermore, most sewer cameras available to nonprofessionals allow you to view only a few feet inside the drain. Finally, if you purchase one of these and find some problems, it's likely you'll have to call in a professional anyway to deal with them.

These devices usually have a small video screen that renders the camera's view and helps to identify root intrusion, pipe corrosion, or other areas that need repair or may be causing a blockage.

Professionals use a locator in tandem with a sewer camera; the locator resembles a metal detector and can identify the location of the underground sensor on the camera in order to see exactly where your sewer line is located.

Once the plumber finds the sewer line and identifies the problem, it may be possible to clear the line using a mainline sewer machine, which can blast out a blockage. In other cases, however, a section of the pipe will need to be accessed directly to deal with a blockage or will even need to be replaced if it cannot be repaired. If you have a clog due to something having been flushed down the toilet, the sewer camera can snake directly down into the toilet and through its exit pipe to inspect the problem.

Most newer homes have what is called a "sewer cleanout," which is a capped pipe sticking up from the ground a few inches, allowing access to the sewer line and thus to pipes both inside and outside your house. If your home has one — and it may be hard to find or covered by dirt — it is usually an easy matter to clear and drain the line. A sewer camera can identify the location of a cleanout. If your home has no cleanout, consider installing one, which will prevent a lot of headaches down the road.