Published by All Systems Pros · Updated October 12, 2026
What Causes Tree Roots in Sewer Lines?
Tree roots enter sewer lines because the pipes contain moisture, oxygen, and nutrients. Roots seek out tiny cracks or loose joints in underground plumbing, expanding as they grow and eventually causing severe blockages or pipe damage.
Older homes in the Foothill communities often have mature trees planted near aging sewer laterals. Materials like clay or cast iron, which were commonly used in older construction, naturally degrade, settle, or shift over time. When a pipe joint separates even slightly, or a hairline crack forms, warm water vapor escapes into the surrounding soil.
Tree roots naturally grow toward moisture and nutrients, following this vapor trail directly to the source. Once they reach the pipe, hair-like feeder roots infiltrate the tiny openings. Inside the pipe, they find a constant supply of water, oxygen, and organic material, causing them to grow rapidly. These roots act like a net, catching passing debris, grease, and toilet paper. As the root mass expands, it restricts the flow of wastewater, eventually leading to a complete blockage.
Signs You Have Roots in Your Plumbing
Common signs of root intrusion include slow draining fixtures, gurgling sounds from toilets, foul odors in the yard or home, and recurring backups that affect multiple drains simultaneously.
Because tree roots grow gradually, the symptoms of an intrusion often start small and worsen over time. A single slow drain might just be a local clog in a P-trap, but if the lowest drains in the house begin to back up when you use plumbing elsewhere, the main sewer line is likely compromised. For example, if you flush a toilet and water backs up into a ground-floor shower or bathtub, the blockage is located deep in the main lateral.
You might also hear gurgling sounds coming from toilet bowls when a washing machine drains. In severe cases, foul sewage odors can become noticeable in the yard or inside the home. Additionally, sinkholes or unusually lush, green patches of grass in your yard can indicate that wastewater is leaking from a root-damaged pipe underground, fertilizing the soil above it.
Who Is Responsible for the Sewer Lateral?
Property owners are typically responsible for maintaining the entire sewer lateral, from the house all the way to the connection at the city main, including the section located under the public street or sidewalk.
A common misconception is that the city is responsible for the portion of the sewer line located beyond the property line. However, local regulations in the San Gabriel Valley and surrounding areas place the burden of sewer lateral maintenance entirely on the homeowner. In Pasadena, the property owner must maintain the house sewer all the way through the connection to the city sewer main.
The city of Glendale's sewer plan dictates that the owner is responsible for the entire lateral, including the wye or saddle connection to the main line. Similarly, the Monrovia municipal code states the owner maintains the lateral including the junction to the main. Los Angeles County provides the same guidance for unincorporated areas like Altadena, noting the owner is responsible for the connection from the house to the street and any blockages up to the main. If tree roots block or break the pipe in the public right-of-way, the homeowner must address it, which requires specific permissions distinct from standard plumbing permits.
What Happens If Root Intrusion Is Ignored?
Ignoring tree roots in a sewer line leads to complete pipe blockages, raw sewage backing up into the home, and eventual structural collapse of the pipe, requiring extensive and costly excavation to replace.
Roots do not stop growing once they find a reliable water source. They will continue to expand, exerting immense physical pressure on the fragile pipe walls. Over time, this pressure can shatter older clay and cast iron pipes. When a pipe completely collapses, routine drain clearing is no longer an option, and the line can no longer transport wastewater away from the home.
A collapsed line means raw sewage has nowhere to go but backward, creating a severe health hazard inside the residence. Contact with raw sewage exposes occupants to dangerous pathogens and bacteria. If a sewage backup occurs in your home, it is critical to avoid the contaminated area, keep children and pets away, and seek professional plumbing assistance immediately. Do not attempt to clean up extensive raw sewage without proper protective equipment, and never enter flooded areas where electrical outlets or appliances might be submerged.
How Professionals Address Root Intrusions
Plumbers use sewer camera inspections to locate the roots, followed by mechanical augers or hydro jetting to clear the blockage. If the pipe is damaged, trenchless or traditional replacement methods are required.
The first step in addressing a suspected root intrusion is a visual inspection using a specialized sewer camera. This allows a professional to determine the exact location, size, and severity of the root mass without unnecessary digging. If the pipe structure is still intact, plumbers can use mechanical augers or high-pressure hydro jetting to cut through and clear the roots, restoring flow.
However, because the original crack or separated joint remains open to the soil, roots will eventually grow back into the pipe. For a permanent solution, the damaged section of the pipe must be repaired or replaced using traditional excavation or trenchless sewer replacement methods. It is important to note that while routine clearing of stoppages may be exempt from permits in jurisdictions like Burbank, structural alterations and pipe replacements require formal approval and inspection from the local building department to ensure code compliance.
Sources and further reading
About All Systems Pros
All Systems Pros is a plumbing service company based in Monrovia, CA. The company lists Rheem ProPartner, A. O. Smith Certified Contractor, and Raypak credentials. These general guides help explain plumbing topics; equipment instructions and project requirements must be checked for the specific property.
