There are many things that can cause a sewer line to get clogged. These include:

1. Broken/ Faulty Pipes

   When a drain line gets old, becomes corroded or breaks, it can cause a sewer clog. Faulty pipes cannot drain wastewater efficiently and this sometimes leads to sewer clogs.
   For example, corroded pipes may leak wastewater and cause it to pool around the pipe which in turn causes the wastewater to flow backward. At other times, broken pipes may get clogged when the soil from the surrounding areas get inside it.

2. Pouring Grease and Oil Down Your Drain

   Grease and oil are some of the most common causes of sewer clogs. This is because grease and oil cool and solidify on the inner surfaces of drain lines. As the layers of oil and grease build up over time, they cause your drain line to get clogged.

3. Hair

   When it comes to clogged drains in bathrooms, the main cause is usually hair. While there isn’t much anyone can do to keep hair from getting into drains, everyone should always regularly clean their drains using solvents or hot water.

4. Sagging Drain Lines

   These are often caused by the shifting of soil that’s under the drain lines or by continuous application of downward pressure from the surface by heavy machinery or parked vehicles.
   Sagging drain lines cause sewer clogs when wastewater pools at the point where the pipe is bent downwards. Once wastewater pools here, it causes a sewer clog and the backflow of wastewater.

5. Flushing Debris Down the Toilet

   Most sewer clogs are caused by flushing down waste such as paper, diapers, and sanitary towels down the toilet. This can cause some serious clogs as plumbing systems are not designed to handle such waste materials.
   Paper, diapers, and sanitary towels do not break down or dissolve in water. More often than not, this causes them to totally block drain lines.

6. Root Intrusion

   Root intrusion is usually caused by leaking pipes. When a drain line leaks, it saturates the surrounding soil with wastewater that is rich in nutrients. This attracts vegetation and tree roots which can cause sewer clogs that further destroy your drain line.