This may seem like a strange question to ask and it’s likely that most people would be unable to answer it. In fact, you may even wonder why this is important to know and if this information will ever have any practical value. But, we rely on our sewer lines every day to take the waste and wastewater out of our homes and out to the main sewer. A sewer line would ideally be located near the surface for easier access during an emergency. For many reasons, this is simply not possible and in most states, it can get you into trouble with the authorities. If you need to dig up or bury a sewer line or you want to know the depth and location this article should help.
Why is the Depth of the Sewer Line Important?
Access to the sewer line is needed to fix or replace sections of the pipe and this is labor intensive work. During a sewer excavation project, it’s not unusual to have 2-3 plumbers working on the line with all their associated equipment nearby. Aside from the disruption to your home, this can be expensive and it may cost thousands of dollars to complete the work. So, it’s important to keep the sewer line away from the surface of your yard to prevent casual damage from a variety of sources. Let’s examine three common sources of sewer line damage in more detail, they are:
- Weather Damage: In areas that are prone to severe natural weather events such as hurricanes, tornadoes, and typhoons, trees are often uprooted. The water may soften the ground and the strong lateral winds can shake the tree loose. If a tree is uprooted in this way it brings the root system with it and this can damage nearby sewer lines.
- Cold Weather: During a harsh winter the sewer line can freeze and break if it’s located too near the surface. The sewer line trench needs to be deep enough to pass the frost line or frost depth point.
- Broken Pipes: Even if your home is located in a warmer climate it can still be damaged if it’s located too close to the surface of your yard. When you’re working outside with tools and you drop them, this can cause compression in the soil. It doesn’t take much force to damage a sewer line and this is especially true if it’s already old and worn.
It’s also important to understand that there are significant penalties that can be incurred if a sewer line is not up to local, county, or state codes.
How Deep are Your Sewer Lines?
This is a hard question to answer accurately because every home is a little different. But, there is some consensus about the ideal depth amongst plumbing professionals. One of the primary concerns is the year round climate which must be understood fully to determine the frost line. This is the depth at which the groundwater freezes and this can vary a great deal even across the same region. The National Weather Service details the frost depth for your area if you put your ZIP code into their handy search tool. But, there are some general rules to follow if you live in a warm or cold climate, they are:
1. Sewer Line Depth in Warm Regions
The variation of sewer line depth in warmer regions isn’t as great because ground freezing is less likely. But, this can create other problems, in February 2021 an unexpected severe cold snap in Texas caused tens of millions of dollars in damaged pipes. In warmer climes, the minimum sewer line pipe depth is set at 30” or 18” under a pavement. This will ensure that the pipe is deeper than the frost line in most areas.
2. Sewer Line Depth in Cold Regions
In Northern regions, homeowners need to bury their sewer lines in deeper trenches to prevent freezing. The colder climate means that the ground can freeze to a greater depth than the South and Southwest of the country. The sewer line needs those extra inches of dirt on top to improve the protection and to get under the frost line. As an extreme example: the underground frost line in Minnesota is a whopping 80” to prevent the sewer pipe from freezing. Again, the exact depth requirements can vary a great deal and the local area frost line depth should always be checked before work can commence.
How Can I Learn More About Local Sewer Line Depth Requirements?
Aside from the aforementioned National Weather Service website, there are two main points of contact to ask questions such as: “What is the best depth for my sewer line?” and “Where is my sewer line buried?”. These are your local municipality and your local professional plumbing company.
1. The Local Municipality
If you call your local city engineering department they can answer a lot of sewer line questions for your neighborhood. Another option is to contact the zoning office and they may have the sewer line locations and the depth for your area. In many cases, it may be possible to obtain a copy of your property map or other helpful documentation.
2. The Local Plumbing Company
Establishing a working relationship with a reputable local plumbing company before you need their services is a smart decision. A local plumber will have excavators and drain line experts on staff that understand the codes for your locality. They also have access to specialized tools such as drain line cameras that they can use to inspect your sewer line. This will give you detailed feedback on the depth, location, and general health of your sewer line. If there is a problem, it may be possible to carry out a trenchless repair to minimize disruption and lower the costs.
Some Final Thoughts
Installing or repairing a sewer line during the winter is a tough job without experience and specialized tools. It’s a better idea to inspect the sewer line and carry out essential work when the weather is better. But, if you do experience a problem, your local plumber can help you to fix your sewer line at any time.