When the main sewer line becomes blocked, wastewater from your home has nowhere to go. Instead of flowing smoothly out to the city’s sewage system, it looks for the path of least resistance. 

Since the bathtub drain is often one of the lowest points in your plumbing, that's where the sewage ends up making its unwelcome appearance.

Common factors behind these clogs include:

Accumulation of Fats, Oils, and Grease: These substances can solidify in the pipes, narrowing the pathway for wastewater until a blockage forms.

Intrusion of Tree Roots: 

Especially in Denver’s older neighborhoods, roots can snake into even tiny cracks in aging pipes, eventually forming a thick mat that traps other debris and blocks the line.

Non-Flushable Items: Products like sanitary wipes, paper towels, and feminine hygiene products can snag in your pipes, quickly causing stubborn clogs.

Build-Up of Sediment or Debris: Over time, residue and materials like hair or soap scum can accumulate, leading to reduced flow and eventual backups.

No matter the root cause, a blocked main sewer line means water will start pooling wherever it can, so if you notice sewage coming up in your tub whenever you flush a toilet or run a sink, it’s a telltale sign of this serious issue. Immediate attention from a professional is crucial to prevent a much bigger headache—like extensive water damage or costly repairs.

Great question—if you’re noticing sewage making its unwelcome debut in your bathtub instead of, say, your kitchen sink or toilet, you’re witnessing plumbing logic in action. 

The bathtub is often the lowest fixture in your home’s drainage system. When a clog forms in the main sewer line—possibly from tree roots, fats, or the dreaded flushable wipes—wastewater looks for the path of least resistance. Because gravity never takes a day off, your bathtub’s drain becomes the perfect exit point.

If you see backflow here and, especially, if it’s happening in more than one drain, it’s a major red flag for a deeper blockage. Main line clogs usually don’t play favorites: all the lowest drains are vulnerable, but bathtubs are common because of their elevation relative to the rest of your plumbing.

Why a Sewer Inspection Matters After a Sewage Backup

Once you’ve tackled the mess and cleaned your bathtub, it’s wise not to stop there. Scheduling a sewer inspection after a sewage backup is a smart step toward preventing future headaches. Even if everything seems fine on the surface, hidden troubles like small cracks, pipe collapse, or stealthy tree roots could be lurking deeper in your plumbing.

By having your sewer line professionally inspected, you get a clear picture of its overall health and can catch potential issues before they escalate into messier, pricier problems. 

Think of it as a routine check-up for your home’s plumbing—early detection means you’re far less likely to deal with another unpleasant surprise in the tub down the line.

How Can I Tell If the Problem Is Limited to My Bathtub?

To figure out whether the sewage backup is just an isolated issue with your bathtub or something more widespread, start by checking the other drains in your home. Is water backing up in your sinks, toilets, or even your laundry drain?

 If you notice that more than just the bathtub is having drainage issues, chances are the main sewer line is blocked and not just the individual tub pipe.

A quick checklist to help you diagnose:

Flush the toilet: Watch to see if water bubbles up in the bathtub or nearby drains.

Run water in sinks: Note if water drains slowly or backs up elsewhere.

Check for odors: Strong sewage smells throughout the house usually signal a main line issue.

If only the tub is acting up and everything else in the house is draining normally, the blockage may be local to that bathroom. 

However, if multiple drains are involved, it’s most likely time for a professional inspection of your main sewer line.

What to Look For When Checking Bathtub Drain Blockages

If you suspect your bathtub is suffering from a clog, the first step is to look for any obvious signs of trouble right at the drain. 

Put on a pair of gloves and carefully inspect the drain opening for hair, soap scum, or foreign objects that might be sitting just beneath the surface. Oftentimes, a visible blockage can be removed with your fingers or with tweezers.

For a more thorough check, take a standard plunger and try to dislodge anything that might be lurking just out of sight. Sometimes, especially with older bathtubs or long-haired households, a simple Zip-It tool or a drain snake from your local hardware store (think: RIDGID, Liquid-Plumr, or Cobra Products) can reach deeper into the pipe and hook out stubborn clumps of hair or accumulated grime.

Don’t force anything if it doesn’t come out easily—if you encounter resistance, it may be an indication of a more serious problem deeper in the plumbing system. In these cases, proceed with caution and consider the help of a professional to avoid causing any extra damage to your pipes.

Blocked Vent Pipes and Sewage Backups in the Bathtub

Another factor to consider is the condition of your vent pipes. These pipes play a crucial role in your plumbing system by regulating air pressure and allowing wastewater to flow smoothly through the drains. 

When vent pipes become clogged—whether due to debris, bird nests, or leaves—the plumbing system can’t “breathe” correctly. 

This blockage creates negative pressure in your pipes, which can actually force sewage back up into your bathtub or shower drain. That unpleasant gurgling or bubbling is often a red flag. 

If you suspect your vent pipes are the culprit, it’s best to leave the inspection and clearing to a professional plumber, as the process can be tricky and involves working on your roof or upper exterior of the house.

How Much Does It Cost to Fix a Clogged Sewer Line?

The cost to fix a clogged sewer line can vary quite a bit, depending on just how stubborn the blockage is and what it takes to clear it. For minor clogs, you might get away with a simple snaking or augering, 

This can range from $100 to $300. More severe blockages that require hydro jetting or even replacing a section of pipe can push costs anywhere from $500 up to a few thousand dollars, especially if excavation is necessary.

It’s always smart to get a professional inspection first, as companies like Roto-Rooter or your local licensed plumber can provide an accurate diagnosis and present your options up front. 

Many also offer video inspections for a flat rate, so you know exactly what you’re dealing with before any work starts. And remember—investing in timely repairs might save you from much more costly damage to your home down the road!

We use the top-of-the-line camera to inspect your sewer lines. This allows us to look through your sewer lines with the sewer scope camera to tell whether tree roots, clogs, scale, cracks, debris, slope issues, bellies, sewer channels, or other issues in the sewer line cause the sewer backup.

Often, tree roots searching for moisture are a major culprit—they can invade pipes and cause stubborn blockages, sometimes leading to messy problems like your toilet backing up into the bathtub or sewage making an unwelcome appearance in your tub. 

Over time, roots gradually grow into small pipe cracks, eventually creating severe restrictions that only a professional sewer camera inspection can detect and resolve. By pinpointing these problems early, you can avoid costly repairs and keep your plumbing running smoothly.

We use the top-of-the-line camera to inspect your sewer lines. This allows us to look through your sewer lines with the sewer scope camera to tell whether tree roots, clogs, scale, cracks, debris, slope issues, bellies, sewer channels, or other issues in the sewer line cause the sewer backup.

Cracked or damaged pipes are a common culprit behind sewer problems. Over time, pipes can become compromised by age, shifting ground, or even the relentless growth of roots, resulting in hidden damage that restricts water flow. This can lead to telltale signs like slow draining, gurgling sounds from the pipes, or even water backing up in your tub or floor drains. 

By spotting these pipe defects early with our advanced camera technology, you can address blockages and minimize costly repairs down the line.

We can even send you a video of your inspection. Call 720-322-4845