5 Signs Your Main Sewer Line Is Failing (and What Denver Homeowners Should Do)
Your main sewer line carries every gallon that leaves your house, so when it starts to fail, the warning signs show up all over the home. Catching them early can mean the difference between a cleaning and a dig. Here are the five signs we see most often in Denver-area homes — and what each one usually means.
1. Gurgling Toilets and Drains
If a toilet gurgles when the washing machine drains, or the tub bubbles when someone flushes, waste is struggling to get past a restriction in the main line. The trapped air escapes through the nearest water trap. Occasional gurgling from one fixture can be a local vent or drain issue; gurgling across several fixtures points toward the main.
2. Several Slow Drains at the Same Time
One slow sink is usually a local clog. When the kitchen sink, shower, and toilets all slow down together, the problem is almost always downstream of where those branches meet — in the main sewer line. We go deeper on this in why multiple drains back up at once.
3. Backups in Your Lowest Drains
Sewage rising out of a basement floor drain, a lower-level shower, or a basement toilet is one of the clearest signs of a main line blockage. Wastewater backs up to the lowest opening it can reach. This is the sign not to wait on: stop using water and call for emergency plumbing.
4. A Soggy Lawn or Unusually Green Strip
A cracked or separated sewer line leaks into the soil. In the yard, that can look like a damp patch that never dries, a depression forming over the pipe's path, or a strip of grass that grows greener and faster than the rest — it's being fertilized from below.
5. Sewer Smells Inside or Outside
A persistent rotten-egg or sewage odor can come from a dry floor-drain trap, but it can also mean sewer gas is escaping from a cracked line or a failed joint. If refilling traps doesn't fix the smell, the line itself should be checked.
Why a Camera Inspection Comes Before Any Repair
Symptoms tell you something is wrong. Only a camera tells you what and where. During a sewer camera inspection, we run a high-resolution camera through your line from the cleanout and record:
- The pipe material (clay, cast iron, Orangeburg, or PVC)
- Roots, grease, scale, or debris restricting flow
- Cracks, offset joints, sags (bellies), or collapsed sections
- The distance from the cleanout to any defect, so it can be located from the surface
Many problems — roots, grease, and buildup — can be cleared with hydro-jetting and professional cleaning. When the camera shows structural damage, you'll have footage and measurements to make an informed decision and compare repair options.
Why Sewer Lines Fail Across the Front Range
| Cause | What it does | Common in |
|---|---|---|
| Tree roots | Enter joints and cracks, then grow into blockages | Older, tree-lined neighborhoods |
| Expansive clay soil | Shifts pipes, offsets joints, creates low spots | Much of the Front Range |
| Aging clay or cast iron | Cracks, corrodes, and scales inside | Homes built before the 1970s |
| Orangeburg pipe | Softens and deforms into an oval or collapses | Many mid-century homes |
| Grease and wipes | Builds up and catches debris | Any home |
Who Pays If the Line Is Broken?
In Denver, homeowners are generally responsible for the private sewer line all the way to the public main — even under the street. Read who pays for a broken sewer line in Denver, and check whether your policy helps in our homeowners insurance guide.
Serving the Entire Denver Metro
Imperial Plumbing LLC is based in Centennial and works across the Denver metro, including:
Frequently Asked Questions
What is the most common first sign of a main sewer line problem?
Gurgling from a toilet or drain when another fixture is used is often the earliest sign. It means air is being pushed through the water traps because waste can't flow freely down the main line.
Can a main sewer line problem fix itself?
No. A partial blockage may seem to clear for a while, but roots, buildup, and pipe defects keep getting worse. Recurring symptoms are a reason to inspect the line rather than wait.
Why does sewage come up in my basement floor drain first?
The floor drain is usually the lowest fixture in the house. When the main line is blocked, wastewater backs up to the lowest opening it can reach.
Does a soggy spot in my yard mean my sewer line is broken?
It can. A damp area that doesn't dry out, or a patch of grass that grows noticeably greener and faster, can mean the line is leaking underground. A camera inspection can confirm whether the sewer is the source.
How long does a sewer camera inspection take?
Most residential inspections take about an hour, depending on access to a cleanout and the length of the line. We review what we find with you on the spot.