Main Sewer Line Clogs: Causes, Prevention, and Solutions

Imagine waking up to a flooded basement or a backed-up toilet – a homeowner’s nightmare. One of the most common culprits behind these unpleasant scenarios is a clogged main sewer line. This crucial pipe carries all the wastewater from your home to the municipal sewer system or septic tank. When it becomes blocked, the consequences can be messy, smelly, and potentially costly.

In this article, we’ll explore the various causes of main sewer line clogs, preventive measures you can take, and effective solutions to tackle these stubborn blockages. By understanding the root causes and taking proactive steps, you can minimize the risk of dealing with a sewer line backup and ensure the smooth flow of wastewater from your home.

Causes of Main Sewer Line Clogs

  1. Tree Roots

One of the most prevalent causes of main sewer line clogs is the intrusion of tree roots. Trees are naturally drawn to the moisture and nutrients present in sewer lines, and their roots can grow through even the smallest cracks or joints in the pipes. As the roots continue to grow and expand, they can create significant blockages, causing wastewater to back up and potentially leading to costly repairs.

  1. Grease, Oil, and Fat (FOG) Buildup

While it may seem harmless to pour grease, oil, and fat (FOG) down the drain, these substances can wreak havoc on your main sewer line. As they cool and solidify inside the pipes, they create a sticky buildup that attracts other debris, leading to clogs over time. This issue is particularly common in households that frequently cook with oils or dispose of greasy food waste improperly.

  1. Non-Biodegradable Items

Flushing non-biodegradable items down the toilet or drain is a surefire way to invite main sewer line clogs. Items like wipes (even those labeled as “flushable”), sanitary napkins, diapers, and cotton swabs can easily get stuck in the pipes, causing blockages and backups. These items do not break down like toilet paper and can quickly accumulate, creating a stubborn clog.

  1. Foreign Objects

Accidentally flushing or dropping foreign objects down the drain can also lead to main sewer line clogs. Toys, jewelry, clothing items, and other household objects can easily find their way into the pipes, causing obstructions and backups. It’s essential to be mindful of what goes down the drain and to keep a close eye on curious little ones who may inadvertently flush objects.

  1. Aging or Damaged Pipes

Over time, the pipes that make up your main sewer line can deteriorate due to age, corrosion, or external factors like shifting soil or tree root intrusion. Older pipes made of materials like clay or cast iron are particularly susceptible to cracking, breaking, or collapsing, which can lead to blockages and backups. Even modern pipes can develop issues if they were improperly installed or subjected to excessive stress.

  1. Bellied or Sagging Pipes

In some cases, sections of the main sewer line can sag or belly, creating low spots where debris and wastewater accumulate. These low points can act as traps, allowing solid materials to settle and eventually cause a clog. Bellied or sagging pipes are often the result of improper installation, soil settlement, or the weight of the pipes themselves over time.

  1. Improper Plumbing Connections

Poorly connected or improperly installed plumbing can also contribute to main sewer line clogs. If the connections between pipes are not properly sealed or aligned, it can create opportunities for debris to accumulate and cause blockages. Additionally, improper installation can lead to issues like bellied or sagging pipes, further exacerbating the problem.

Prevention: Keeping Your Main Sewer Line Clear

While main sewer line clogs can be a frustrating and messy problem, there are several preventive measures you can take to minimize the risk of encountering them:

  1. Be Mindful of What Goes Down the Drain

One of the most effective ways to prevent main sewer line clogs is to be mindful of what you flush or pour down the drain. Avoid flushing non-biodegradable items like wipes, sanitary products, and diapers, as well as foreign objects like toys or jewelry. Additionally, refrain from pouring grease, oil, and fat down the drain, as these substances can solidify and contribute to clogs.

  1. Install a Grease Trap

If your household frequently cooks with oils or generates a significant amount of greasy waste, consider installing a grease trap. These devices are designed to capture and separate grease, oil, and fat from the wastewater before it enters the main sewer line, preventing buildup and clogs.

  1. Schedule Regular Sewer Line Inspections

Preventive maintenance is key to keeping your main sewer line in good condition. Consider scheduling regular sewer line inspections with a professional plumber. During these inspections, they can use specialized cameras to identify potential issues, such as tree root intrusion, bellied pipes, or buildup, and address them before they become major problems.

  1. Maintain Proper Landscaping

If you have trees or large shrubs near your main sewer line, it’s essential to maintain proper landscaping. Trim or remove any roots that may be growing towards the pipes, as they can eventually penetrate and cause clogs. Additionally, consider replacing problematic trees with species that have less invasive root systems.

  1. Use Enzyme or Bacterial Drain Cleaners

Instead of relying on harsh chemical drain cleaners, which can damage your pipes, consider using enzyme or bacterial drain cleaners. These products contain natural bacteria or enzymes that break down organic matter, helping to keep your pipes clear and free-flowing.

Solutions: Tackling Main Sewer Line Clogs

Despite your best efforts, main sewer line clogs can still occur. When faced with a clogged sewer line, it’s essential to act quickly to minimize the potential for backups and water damage. Here are some effective solutions to consider:

  1. Use a Drain Snake or Auger

For minor clogs in sinks or bathtubs, you can try using a drain snake or auger to clear the blockage. These flexible cables with a corkscrew-like end can be inserted into the drain and rotated to dislodge or break up the clog. However, for main sewer line clogs, professional equipment and expertise may be required.

  1. Hydro Jetting

Hydro jetting is a powerful and effective method for clearing stubborn main sewer line clogs. This process involves using high-pressure water jets to blast through and dislodge even the most stubborn blockages. Professional plumbers have access to specialized hydro jetting equipment that can effectively clear clogs without causing damage to your pipes.

  1. Video Camera Inspection

Before attempting to clear a main sewer line clog, it’s essential to identify the exact cause and location of the blockage. Professional plumbers can use specialized video cameras to inspect the inside of your pipes, providing a clear visual of the clog and any potential issues, such as tree root intrusion or pipe damage. This information can help them determine the most appropriate course of action.

  1. Pipe Relining or Replacement

In cases where the main sewer line is severely damaged or collapsed, relining or replacing the pipes may be necessary. Pipe relining involves inserting a new, seamless pipe lining into the existing pipe, effectively creating a new pipe within the old one. This method is often more cost-effective and less disruptive than traditional pipe replacement.

However, if the damage is too extensive or the pipes are too old, complete replacement may be the only viable solution. This process involves excavating and removing the old pipes and installing new ones, which can be a more invasive and costly undertaking.

  1. Tree Root Removal

If tree roots are the culprit behind your main sewer line clog, specialized techniques may be required to remove them. Professional plumbers can use chemical treatments or mechanical methods, such as root cutters or hydro jetting, to eliminate the roots and clear the blockage. It’s important to address the root issue (pun intended) to prevent future clogs from occurring.

  1. Install a Backflow Prevention Device

To minimize the risk of sewage backups and water damage in the event of a main sewer line clog, consider installing a backflow prevention device. These devices are designed to prevent wastewater from flowing back into your home, providing an additional layer of protection against messy and potentially hazardous backups.

  1. Seek Professional Assistance

While some minor clogs may be addressed with DIY methods, it’s generally recommended to seek professional assistance when dealing with main sewer line clogs. Experienced plumbers have the necessary tools, equipment, and expertise to diagnose and resolve these issues effectively and safely. Attempting to clear a major clog on your own can potentially cause further damage or exacerbate the problem.


Main sewer line clogs can be a frustrating and potentially costly issue for homeowners. By understanding the various causes, such as tree root intrusion, grease buildup, non-biodegradable items, and aging pipes, you can take proactive steps to prevent these blockages from occurring.

Implementing preventive measures like being mindful of what goes down the drain, installing a grease trap, scheduling regular inspections, and maintaining proper landscaping can go a long way in keeping your main sewer line clear and functioning properly.

However, when a clog does occur, it’s essential to act quickly and seek professional assistance. Solutions like hydro jetting, video camera inspections, pipe relining or replacement, and tree root removal can effectively resolve even the most stubborn blockages.

Remember, a well-maintained and properly functioning main sewer line is crucial for the smooth operation of your home’s plumbing system and the prevention of messy backups and water damage. By taking a proactive approach and addressing issues promptly, you can minimize the risk of dealing with the unpleasant consequences of a clogged main sewer line.

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