The Stinky Truth About Why Your Sewer Line is Overflowing

The Stinky Truth: What a Sewer Line Backup Really Means for Your Home

A sewer line backup happens when wastewater can’t flow forward through your sewer system — so it reverses direction and comes back up into your home through drains, toilets, and floor drains.

Here’s what you need to know right now:

1. Stop using all water immediately — no toilets, showers, sinks, or laundry
2. Stay out of the affected area — sewage contains dangerous bacteria, viruses, and pathogens
3. Turn off electricity to any area where water is present
4. Document the damage with photos before touching anything
5. Call a professional — sewage cleanup is a health emergency, not a DIY job

This isn’t just a plumbing inconvenience. Backed-up sewage can cause thousands of dollars in damage to floors, walls, electrical systems, and personal belongings. And it’s happening more often — sewer backups are increasing at roughly 3% per year, driven by aging infrastructure. The nation’s sewer lines average over 30 years old, and many are well past their useful life.

For Denver Metro homeowners, the risk is real and urgent.

I’m Cole Nudel, a disaster restoration professional with A1 Water Damage Restorations in the Denver area, where I’ve worked hands-on with property owners navigating the chaos of a sewer line backup and its aftermath. In this guide, I’ll walk you through exactly what’s causing your backup, what to do about it, and how to make sure it doesn’t happen again.

Understanding the Crisis: What is a Sewer Backup?

When we talk about a sewer line backup, we aren’t just talking about a stubborn toilet that needs a quick plunge. We are talking about a systemic failure where the very pipes designed to carry waste away from your home decide to send it back. This wastewater reversal is often a “black water” event, meaning the liquid contains human waste, chemicals, and hazardous pathogens.

The damage caused by these events is often extensive. Beyond the obvious “ick” factor, sewage saturates drywall, seeps under flooring, and ruins electrical systems. If not addressed within 24 to 48 hours, the moisture leads to rapid mold growth and structural rot. In our experience serving the Denver Metro Area—from the historic streets of Golden to the modern developments in Broomfield—the structural impact can be devastating if the water reaches the foundation or support beams.

Home Lateral vs. City Main

It is vital to understand where the responsibility lies. Every home has a “sewer lateral”—the pipe that connects your house to the municipal sewer system.

• The Sewer Lateral: This is the portion of the pipe that runs from your home to the city’s main line. In almost all cases in Colorado, including Westminster and Arvada, the homeowner is responsible for the maintenance and repair of this lateral, even the part that sits under the public sidewalk or street.
• The City Main: This is the large public pipe that collects waste from the entire neighborhood. If the city main is blocked, multiple houses on your street will likely experience backups simultaneously.

As of April 2026, the infrastructure in many of our local communities is under significant stress. With over 500,000 miles of sewer lines across the nation averaging over 30 years in age, many systems are simply reaching their breaking point. For more technical details on how these systems interact, you can view resources like Sewage Backups | Pittsburgh Water.

Common Causes of a sewer line backup

Why does this happen? It rarely occurs for just one reason. Usually, it is a combination of environmental factors and household habits.

1. Tree Root Intrusion

This is perhaps the most common cause we see in older neighborhoods like Littleton and Cherry Creek. Tree roots are naturally drawn to the moisture and nutrients found inside sewer pipes. They can enter through tiny cracks or loose joints, eventually growing into massive “root balls” that act like a net, catching grease and debris until the pipe is completely choked.

2. Fat, Oil, and Grease (FOG)

Many homeowners treat their kitchen sink like a trash can. When you pour warm grease or oil down the drain, it eventually cools and solidifies, sticking to the walls of the pipe. Over time, this “fatberg” narrows the passage until even a single flush can trigger a sewer line backup.

3. Aging and Material Failure (The Orangeburg Issue)

In historic areas of Downtown Denver and surrounding older neighborhoods, many homes were built with “Orangeburg” pipes. Used primarily from the 1940s through the 1970s, these are essentially compressed tar-paper pipes. They were cheap at the time but are now well past their 50-year lifespan. They are prone to collapsing under the weight of the soil or being crushed by shifting ground.

4. Shifting Soils and Heavy Rainfall

Colorado is known for its “expansive” soils, particularly in Southeast Denver and Aurora. As the ground expands and contracts with moisture levels, it puts immense pressure on underground pipes, leading to cracks or “bellies” (low spots where waste settles). When we get heavy spring or summer downpours, the influx of stormwater can overwhelm combined sewer systems, forcing raw sewage into basements and floor drains.

Cause Type	Examples	Responsibility
Residential	Grease buildup, flushing wipes, tree roots in lateral	Homeowner
Municipal	Main line blockage, lift station failure, storm overload	City/Utility
Environmental	Shifting soil, heavy rain, pipe corrosion	Varies

Recognizing the Warning Signs

A sewer line backup doesn’t always happen in a sudden explosion of water. Often, your home will try to warn you that trouble is brewing.

• Gurgling Sounds: If your toilet bubbles or your shower drain gurgles when you run the washing machine or dishwasher, it’s a sign that air is trapped in the system due to a partial blockage.
• Foul Odors: A persistent smell of rotten eggs or raw sewage near drains or in the basement is a major red flag.
• Slow Drainage: If multiple sinks and tubs are draining slowly despite your best efforts with a plunger, the problem is likely deeper in the main line.
• Lush Lawn Patches: If one area of your yard is suddenly much greener and thicker than the rest—or if you notice a sunken, soggy spot—you likely have a leaking sewer lateral.
• Multiple Fixture Issues: The most telling sign is when using one fixture affects another. For example, flushing the toilet causes water to back up into the bathtub.

If you are noticing these signs in Westminster, you can find localized tips through Sewer Line Backup Warning Signs.

Identifying a Main sewer line backup vs. a Simple Clog

How do you know if you need a bottle of Drano (which we don’t recommend!) or a restoration team?

1. Is it localized? If only the kitchen sink is slow, it’s likely a simple clog in that specific pipe.
2. Is it systemic? If every drain on the lowest level of your home (like the basement or crawlspace) is backing up, you have a main line issue.
3. The “Bounce” Test: Watch the water level in your toilet. If it “bounces” or rises significantly when you run a nearby sink, the venting or main line is compromised.

Immediate Action and Health Risks

If you find yourself standing in an inch of dark, smelly water, don’t panic—but do act fast.

First, stop all water usage. This includes the dishwasher and washing machine. Any water you send down the drain will only add to the puddle on your floor. Next, if the water is anywhere near electrical outlets or your fuse box, turn off the power—but only if you can do so without stepping into the water.

Protective Gear and Documentation

Before you even think about entering the area, you need Personal Protective Equipment (PPE). This means:

• Rubber boots and waterproof gloves
• An N95 mask or respirator
• Eye protection (goggles)

Once you are protected, take photos and videos of everything. You will need this for insurance purposes later. Once the area is documented, call a professional team like us at A1 Water Damage Restorations. We specialize in Sewage Cleanup and can begin the drying and disinfection process immediately.

Pathogens and Exposure Risks

Sewage is classified as “Category 3” water—the most dangerous level. It is teeming with pathogens that can cause serious, long-term illness.

• E. coli and Salmonella: Cause severe gastrointestinal distress.
• Hepatitis A: A serious viral infection of the liver.
• Leptospirosis: Can lead to kidney damage or meningitis.
• Acanthamoeba: Can cause skin infections or respiratory issues.

Because of these risks, any porous materials—like carpets, pads, and upholstered furniture—that have been touched by sewage usually cannot be saved and must be discarded. You have a narrow 48-hour window to get the area professionally sanitized before the health risks escalate and mold becomes a secondary emergency.

Responsibility, Insurance, and Prevention

One of the biggest shocks for homeowners in the Denver Metro Area is realizing that a standard homeowners insurance policy often excludes sewer backups.

Who Pays?

As we mentioned earlier, you are responsible for the sewer lateral. If a tree root on your property collapses your pipe, you are on the hook for the repair. If the city main backs up, the city might be responsible, but proving liability is notoriously difficult and time-consuming.

Most insurance companies offer a “Sewer Backup Rider” or endorsement. This is an add-on to your policy that specifically covers cleanup and restoration for these events. We strongly recommend every homeowner in Boulder, Wheatridge, and Arvada checks their policy today for this coverage. For more on municipal perspectives on these responsibilities, see What to Do After a Sewer Backup | Portland.gov.

How to Prevent a Future sewer line backup

You don’t have to live in fear of the next big rainstorm. Here is how you can protect your home:

1. Install a Backwater Valve: This is a one-way valve installed on your sewer lateral. It allows waste to flow out but automatically closes if it detects water trying to flow back into the house.
2. Proper Disposal Habits: Never flush “flushable” wipes (they aren’t actually flushable!), feminine hygiene products, or paper towels. Scrape your plates into the trash rather than using the garbage disposal for grease.
3. Annual Inspections: Have a plumber perform a camera inspection of your sewer line every 1-2 years, especially if you have mature trees on your property.
4. Root Cutting: If roots are found, a professional can use a mechanical cutter or hydro jetting to clear them out before they cause a total collapse.

If you’ve already experienced a backup and want to ensure your home is fully restored and protected, check out our More info about sewage cleanup services.

Frequently Asked Questions

What is a cross bore and why is it dangerous?

A cross bore occurs when a new utility line (like a natural gas pipe) is accidentally bored directly through an existing sewer pipe. This often happens with “trenchless” technology where the installer can’t see the pipe they are hitting.

This is a massive safety concern. If your sewer backs up and a plumber uses a mechanical “snake” to clear it, the cutting head could rupture the gas line inside your sewer pipe. This sends natural gas into your home, creating a high risk of explosion. If you suspect a backup, always have the line inspected with a camera before using cutting tools.

When should I call a professional plumber?

You should call a professional if you notice recurring backups, if multiple fixtures are affected at once, or if you smell persistent sewage odors. A professional plumber has specialized camera equipment to see exactly what is happening 10 feet underground, which is something a plunger simply can’t do.

Does homeowners insurance cover cleanup costs?

Only if you have a specific “water backup and sump pump overflow” endorsement. Standard policies usually cover “sudden and accidental” water damage (like a burst pipe) but exclude water that comes up from the ground or through the sewer. Always save your professional restoration invoices, as these will be critical for your claim.

Conclusion

A sewer line backup is more than just a mess; it’s a threat to your home’s value and your family’s health. Whether you are dealing with aging Orangeburg pipes in Denver or tree roots in Littleton, the key is swift, professional action.

At A1 Water Damage Restorations, we understand the stress of these emergencies. We are a family-owned, IICRC-certified team providing 24/7 emergency response across the Denver Metro Area—from Boulder to Greenwood Village. We don’t just “clean up” the water; we provide comprehensive restoration to ensure your property is safe, sanitized, and restored better than ever.

Don’t wait for the smell to get worse or the mold to set in. Schedule Sewage Cleanup Now and let our family take care of yours.