sewer pipe frozen above ground - how deep are sewer lines buried

How Deep are Sewer Lines Buried (and Why Do You Need to Know)?

If you’re asking, “How deep are my sewer lines buried?”, then you need to read this article. Because the answer varies a great deal depending on where you live.

Wouldn’t it be great if sewer lines could be buried just a few inches underground? It sure would make digging a trench a lot easier and faster. Unfortunately, that’s not the case. In fact, doing so in nearly every state in the country will get you into a heap of trouble.

If you’re trying to bury or dig up a sewer line, or just want to know where and how deep it is, continue reading for all the answers.

Why is Depth Important?

Digging up or burying a sewer line is labor intensive. That’s why most sewer excavation projects use two or three plumbers plus their equipment. And it’s an expensive process, often costing thousands of dollars.

So, making sure your sewer pipe doesn’t get damaged by being buried too shallow is important. Here are the most common reasons for why you need to know.

  • In cold-weather climates, your sewer line will freeze and break if your trench was not dug deep enough for the pipe to be placed below the frost line (frost depth).
  • In areas where natural events routinely cause damage (tornados, hurricanes, typhoons), wind and water can uproot trees, causing sewer lines to be uprooted with them.
  • Your city can charge you a penalty for not adhering to local, county, or state codes and requirements.
Broken pipe - how deep are sewer lines buried
Even in a warm climate, this pipe doesn’t come close to being buried at an ideal depth. For example, a storm could easily damage the pipe. Even an accidentally dropped hammer could break it, leading to hundreds if not thousands of dollars in expenses. In addition, the pipe is not up to code, which can lead to fines.

How Deep are Sewer Lines Buried?

Unfortunately, the answer is, “it depends.”

Plumbers, the main authority on this subject, believe pipe depth depends on the area’s year-round climate. That begins by knowing the depth of your frost line (or frost depth). It is the depth (in inches) at which water in the ground can be expected to freeze.

frost line depths in the United States - how deep are sewer lines buried
The image above displays general frost depths across the United States. However, you also can determine your specific area’s frost depth by ZIP code here. It is provided by the National Weather Service.

1. How Deep are Sewer Lines Buried in Cold Regions?

People in the North need to bury their sewer line pipes much deeper than those in the South and Southwest. The colder climate in the North means the ground freezes to a greater depth. They need more protection, which is created by being buried under more inches of dirt.

Although an extreme example, Minnesota’s underground frost depth is 80 inches. A pipe in Minnesota should be buried at least 80 inches underground to prevent damage from freezing.

Of course, the number of inches might be less in southern Minnesota than in northern Minnesota, due to slightly lower year-round temperatures. Which is why you should always check your local area for the correct depth.

2. How Deep are Sewer Lines Buried in Warm Regions?

The depth of sewer lines in warm clients doesn’t vary quite as much, and the need for burying the pipe deep isn’t as great.

However, as we saw with the unexpected cold front that hit Texas in February 2021, tens of millions of dollars in pipe damage can occur from just one freezing event. State plumbing codes in Texas, for example, say the minimum depth is 30 inches or 18 inches under pavement.

This indicates that the pipe is buried deeper than the actual frost line no matter where you live.

Who Do I Contact About Sewer Line Depth?

There are two great places to start with any questions about your sewer lines. They can answer questions like, “Where is my sewer line located?” and “How deep should my sewer line be buried?”.

  • Plumbers. Plumbers who have drain specialists and excavators on staff are aware of the codes in your area. In addition, they have specialized tools like sewer line cameras and excavation equipment. A plumber conducting a sewer line camera inspection can find where your main line sewer runs on your property, how deep it is buried, and even clean or repair it if necessary.
  • Municipality. Call your city engineering department. They usually handle sewer line issues for your area. Or, try calling someone in your city’s zoning office. Depending on where you live, they might know exactly where your sewer is located and how deep. They might even be able to give you a copy of any documentation, such as your property map.
plumber working on frozen sewer pipe - how deep are sewer lines buried
Make sure your sewer pipes are buried below the frost line (frost depth) in your specific area. Call a plumber or your municipality to find out the exact depth required.

Final Thoughts

Any plumber with a specialty in repairing, replacing, and installing sewer lines will tell you that fixing a frozen pipe underground in the dead of winter is a really hard job. In fact, we do it all the time.

Don’t let this happen to you. Make sure your sewer pipes are buried where they should be: below the frost line (frost depth) in your specific area. Call a plumber or your municipality to find out the exact depth required.

Call 1-Tom-Plumber

Don’t hesitate to contact us here or call us at 1-Tom-Plumber (1-866-758-6237) if you need help excavating a sewer line trench or burying a pipe at the correct depth.

1-Tom-Plumber’s certified team of plumbers and drain technicians respond immediately to any emergency plumbing, drain cleaning, or water damage problem. We also handle the excavation of underground water lines and sewer main lines. Our immediate-response team is available every day and night of the year, even on holidays.

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