When sewage flows back into your home, things can quickly escalate into a health hazard and costly repair. Sewer backups can happen for several reasons, including clogged drain lines, damaged pipes, tree root intrusion, or problems with a home’s plumbing vent system.
Recognizing early warning signs like unusual drain noises, sewer odors, or toilet water movement can help you address sewer problems before they turn into a full backup. In this guide, we explain what causes sewer backups, what to do if one happens, and how to spot early warning signs, including tips from This Old House plumbing and heating expert Richard Trethewey.
Understanding Sewer Backups
Sewer backups occur when wastewater cannot flow properly through the sewer system, causing it to reverse and enter your home. When this happens, contaminated water may come up through drains, toilets, or floor fixtures, creating both a health hazard and potential property damage.
In most homes, wastewater flows through a main drain pipe that carries waste to a municipal sewer system or septic tank. If that pipe becomes blocked, damaged, or overloaded, wastewater may push back through the lowest plumbing fixtures in the house, such as basement drains or tubs.
Standing water in a sewer line can be a warning sign of a larger drainage issue. “There shouldn’t be any water in a drain line except at the moments when you’re running water or flushing something,” says Richard Trethewey, a plumbing and heating expert, on the “How to Diagnose Plumbing Drain Problems” episode of Ask This Old House.
Common Causes of Sewer Backups
Sewer backups usually happen when something blocks the main drain line or prevents wastewater from flowing out of the home. In other cases, the sewer system itself becomes overwhelmed, forcing wastewater back through household plumbing.
- Aging sewer systems: Older pipes may deteriorate, collapse, or develop leaks over time.
- Broken or cracked pipes: Ground shifting, freezing temperatures, or soil movement can damage underground sewer lines.
- Clogs from improper waste disposal: Flushing nonbiodegradable items or pouring grease down drains can create blockages.
- Heavy rainfall: Municipal sewer systems can become overloaded during major storms, pushing wastewater back toward homes.
- Tree root infiltration: Tree roots naturally grow toward moisture and can enter small cracks in sewer pipes, eventually creating major blockages.
- Pipe sagging (bellied pipes): Sections of sewer pipe that settle or sag can trap water and debris, eventually causing blockages.
Signs Your Sewer Is Backing Up
Early detection can help you address sewer issues before they turn into a full backup. If you notice unusual behavior from your drains or toilets, it may indicate a blockage or venting problem in your plumbing system.
For example, a toilet that moves or “bounces” when another fixture runs can signal trouble inside the drain or vent system. “Anytime I see that water level bounce when you flush the toilet, it suggests something to do with the venting system,” Trethewey says.
Look for these warning signs:
- Foul odors coming from drains or yard
- Gurgling sounds from toilets or drains
- Multiple drains clogging simultaneously
- Water backing up in the shower or tub when using the washing machine
- Wet spots in your yard, especially near the sewer line
Where Sewer Backups Usually Appear
Sewer backups usually happen at the lowest plumbing fixtures in a home because wastewater flows by gravity. When the main sewer line becomes blocked or overwhelmed, wastewater will push back through the lowest available opening in the plumbing system.
Common places where homeowners first notice a backup include:
- Basement floor drains: These are often the lowest drains in the home and a common place for sewage to appear.
- Basement tubs or showers: Wastewater may back up into lower-level bathroom fixtures before affecting upper floors.
- Laundry drains or utility sinks: Washing machine drains can also get impacted if the main sewer line is blocked.
- Lower-level toilets: Toilets in basements or first-floor bathrooms may show early warning signs like bubbling water or slow draining.
If sewage appears in multiple drains at once, the issue likely involves the main sewer line rather than a single clogged fixture.
Immediate Actions To Take
If you suspect a sewer backup, act quickly to prevent contaminated water from spreading through your home. Taking a few immediate steps can help limit damage and reduce health risks while you arrange professional repairs.
Stop Using Water Fixtures
Immediately stop using plumbing fixtures throughout the house. Avoid flushing toilets, running faucets, or using appliances such as dishwashers and washing machines. Continuing to use water can push more wastewater into already blocked pipes and worsen the backup.
Keep People and Pets Away From Affected Areas
Sewage contains harmful bacteria and contaminants. Limit access to affected rooms and keep children and pets away from standing water or contaminated surfaces until cleanup is complete.
Turn Off Electricity if Necessary
If sewage has reached electrical outlets, appliances, or wiring, avoid entering the area and shut off power to the affected circuit if it can be done safely. If you cannot safely access the breaker panel, contact an electrician or emergency services for assistance.
Locate Your Sewer Cleanout
If your home has an outdoor sewer cleanout, opening the cap can sometimes relieve pressure in the line and prevent sewage from backing up inside the house. Only do this if it is safe and accessible.
Contact a Professional Plumber
Sewer backups often involve the main drain line or underground pipes, which require specialized tools to diagnose and repair. A licensed plumber can inspect the sewer line, locate the blockage, and recommend solutions such as drain cleaning, camera inspection, or pipe repair.
Safety Precautions During a Sewer Backup
Dealing with a sewer backup requires caution to protect yourself from harmful contaminants. You must take the proper safety measures before cleaning or entering affected areas.
Protective Gear You Should Wear
Before entering any area affected by sewage, we suggest wearing rubber boots and gloves, protective eyewear, an N95 respirator mark, and disposable coveralls. These items can be disposed of and will protect you from contaminated water. Check that all your protective gear fits properly and covers any exposed skin.
Areas To Avoid in Your Home
Some parts of your home may be unsafe during a sewer backup, including basements or lower levels with standing water, rooms with visible electrical hazards, areas with a strong sewage odor, or spaces with visible mold growth. If possible, seal off these areas to keep contamination from spreading to other parts of your home and hire a professional to clean them.
Types of Sewer Backups
Not all sewer backups originate in the same place. In most homes, the problem will fall into one of two categories: a blockage in the main sewer line or a clog in a smaller branch line inside the home.
Main Line Backups
A main line backup is the more severe type of sewer problem where there’s a blockage in the main line connecting your home to the municipal sewer system. Signs of a main line backup include multiple drains backing up, sewage coming up through floor drains, and backups in the lowest points of the home. Main line backups require professional attention, as they can lead to extensive damage and health hazards.
Secondary Line Backups
Secondary line backups are less severe but still problematic. They occur in individual drain lines within your home. If the problem is limited to a specific room or section of the house, you’re likely dealing with a secondary line backup.
DIY Methods for Clearing Minor Backups
For minor secondary line backups, you can try a few do-it-yourself (DIY) methods before calling a professional. However, if these methods don’t work quickly or if you’re dealing with a main line backup, it’s best to contact a plumber as soon as you can.
Using a Plunger
A plunger can work to clear minor clogs in toilets, sinks, and showers. To use a plunger, make sure there’s enough water to cover the plunger’s head. Create a tight seal around the drain and plunge for about 20 seconds before checking to see if the water drains properly. Repeat the process a few times if necessary, but move to other methods or call a professional if the drain is still clogged.
Employing a Drain Snake
A drain snake, or auger, can reach deeper into pipes to clear blockages. To use one, insert the snake into the drain opening and turn the handle to feed the snake into the pipe until you feel resistance. Continue turning to work through the blockage. Once you feel the clog clear, retract the snake slowly and run hot water to flush and clear the drain. If this doesn’t work, call a professional to avoid damaging your pipes.
Professional Sewer Repair Options
When DIY methods fail, or the backup is too severe, call a professional. Plumbers have the tools and techniques to address sewer issues quickly and safely.
Hydro Jetting
Hydro jetting is a method for clearing stubborn clogs and cleaning sewer lines. This process involves using high-pressure water to scour the inside of pipes. This removes built-up debris, grease, and tree roots to clean the entire pipe diameter. Hydro jetting is effective but should only be performed by professionals to avoid damaging older or fragile pipes.
Pipe Relining
For damaged pipes that don’t require complete replacement, pipe relining is a quicker and less invasive solution. This method creates new pipes within the existing damaged pipes using a resin-saturated liner that hardens and seals into place. Compared to the cost of traditional pipe replacement, it is more cost-effective.
Preventing Future Sewer Backups
Taking proactive measures can reduce the risk of future sewer backups. By implementing regular maintenance and adopting proper waste disposal habits, you can keep your sewer system functioning smoothly.
Regular Sewer Inspections
Scheduling routine sewer system inspections can help detect problems while they are still in the early stages. Addressing minor problems as soon as possible can prevent extensive damage to your pipes. We also suggest an inspection by a professional plumber at least once a year.
Regular inspections can save you money in the long run by preventing costly emergencies. For example, a consistent inspection routine can prevent potential sewer issues due to unpredictable factors like weather-related floods.
Proper Waste Disposal Habits
Many sewer backups are caused by improper waste disposal. Never flush non-biodegradable items like wipes, diapers, or personal care products down your toilet. Avoid pouring grease or oil down drains, and use a strainer in kitchen sinks to catch food particles. You should also dispose of coffee grounds and eggshells in the trash, not your sink.
Dealing with Water Damage
Addressing water damage after a sewer backup can prevent mold growth and structural issues. Quick action can also minimize long-term damage and restoration costs.
Removing Standing Water
The first step in dealing with water damage is removing any standing water, which should be done within the first 48 hours. Use a wet/dry vacuum to remove water from floors and carpets. For larger amounts of water, you could rent a submersible pump. Always wear protective gear and dispose of the water properly, following local regulations for handling contaminated water.
Drying Out Affected Areas
Once standing water is removed, open windows and doors to increase air circulation. Use fans and dehumidifiers to speed up drying and remove wet carpets, padding, and any affected drywall. Most importantly, clean and disinfect surfaces that come in contact with sewage. Professional water damage restoration services may be needed for extensive damage or if the backup occurred more than 24–48 hours ago.
Insurance Considerations for Sewer Backups
Sewer backups can cause significant damage to flooring, drywall, furniture, and personal belongings. However, many homeowners are surprised to learn that standard homeowners insurance policies often do not automatically cover sewer backup damage.
What Homeowners Insurance Might Cover
Most standard homeowners insurance policies cover damage caused by sudden plumbing failures inside the home, such as a burst pipe. However, damage caused by wastewater backing up through drains or sewer lines is often excluded unless additional coverage is purchased.
Because sewer backups frequently originate in underground sewer lines or municipal systems, insurers typically treat them differently from internal plumbing problems.
Specialized Sewer Backup Coverage
Many insurers offer sewer backup endorsements, or riders, that extend coverage to damage caused by wastewater backing up into the home. This coverage typically helps pay for cleanup, repairs to damaged materials, and replacement of affected belongings.
Adding sewer backup coverage is usually inexpensive compared with restoring a home after a sewage backup. Homeowners should review their policy or speak with their insurance provider to understand whether this protection is included.
Home Warranty Coverage for Sewer Repairs
Some homeowners purchase home warranties that include plumbing coverage, which may help pay for repairs to sewer lines or drain lines that fail due to normal wear and tear. Certain providers offer plans specifically designed for underground plumbing, typically listed as sewer line home warranties.
While homeowners insurance may cover damage caused by sewage backups if you add this type of coverage, home warranties typically focus on repairing the plumbing system itself. They usually do not cover damage caused by sewage entering the home, such as ruined flooring, drywall, or personal belongings.
Health Risks Associated with Sewage Exposure
Sewage backups pose serious health risks because wastewater can contain harmful bacteria, viruses, and other contaminants. Contact with contaminated water can lead to illness through skin exposure, accidental ingestion, or breathing in airborne particles during cleanup.
Common health risks include:
- Gastrointestinal illness: Exposure can cause nausea, diarrhea, or stomach cramps.
- Skin infections: Open cuts or scrapes may become infected after contact with sewage.
- Respiratory irritation: Mold growth and airborne contaminants may irritate the lungs or trigger allergies.
Anyone cleaning a sewage backup should wear protective gear and avoid direct contact with contaminated water. If you develop symptoms such as fever, vomiting, or diarrhea after exposure, seek medical attention.
When To Consider Moving Out Temporarily
In severe cases, a sewer backup may temporarily make a home unsafe to occupy. Widespread contamination, strong sewage odors, or damage to electrical systems may require you to leave the home while cleanup and repairs take place.
Situations that may require temporary relocation include:
- Sewage contamination affecting multiple rooms
- Wastewater entering living areas or bedrooms
- Strong odors or lingering contamination after cleanup
- Damage to electrical systems or structural components
If relocation is necessary, consider staying with family or friends or booking a short-term rental. Some homeowners insurance policies may help cover temporary housing costs, depending on the type of damage and coverage included in your policy.
