Why Is Raw Sewage Backing up Into My Basement?

A blockage in the main sewer line that serves your street can send sewage backward into the lowest drain in your home, which is often the basement. Grease, wipes, paper towels, and other items that don't break down easily can collect and form a clog. When the line fills up, wastewater has nowhere to go except back through your pipes.

Tree roots are another common culprit. Roots from nearby trees can grow into cracks or joints in the sewer pipe, gradually narrowing the opening until waste gets caught. Over time, the roots and debris combine into a solid mass. If you notice recurring backups, the root cause may be in the main line rather than inside your own plumbing.

• Flushable wipes and paper towels can clog pipes.
• Grease and cooking oil solidify in sewer lines.
• Tree roots can invade pipe joints and cracks.
• Heavy rainfall can overload the municipal sewer system.
• A broken or collapsed pipe can create a blockage point.

In many areas, the same pipes carry both sewage and stormwater. During a heavy rain, the volume of water can exceed what the sewer system can handle. When the system is overwhelmed, pressure builds and sewage can be forced backward through the lowest openings in your home, which is often the basement floor drain.

If you live in Fresno, the hot semi-arid climate brings long dry spells, but sudden downpours can still flood the system. A backup after a storm suggests the problem may be in the municipal lines rather than your own pipes. You can check whether neighbors have similar issues to confirm that the cause is widespread.

Local water damage pros usually start by removing standing sewage and contaminated materials. They use pumps and wet vacuums to extract the waste, then dispose of it according to local regulations. After that, they clean and disinfect all affected surfaces to reduce health hazards. The process can take several hours or days, depending on how much area is affected.

The pros also assess what caused the backup. They may inspect your pipes with a camera to look for clogs or damage. If the issue is in the main sewer line, you may need to contact your city or municipality. The pros can help with cleanup and repairs inside your home, but they do not fix the municipal system. Check your insurance policy to see if sewage backup coverage is included. Policies vary, and your insurer decides what is covered.