Got a Clogged Sewer Line? Here’s What to Do

By Geoffrey Sperring

October 10, 2025

There can’t be anything worse than having sewage flowing onto your feet when showering. This is usually caused by a clogged drain. It may be tempting to hope that the problem goes away, but unless you fix the underlying problem, the drains will continue to back up. Sewer clogs are a health hazard, and you need professional help to fully resolve the problem.

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What Are the Telltale Signs That a Sewer Line Is Clogged?

Sewer lines don’t block up without warning. Clogged sewer line symptoms include:

Slow drains. Water takes a long time to drain from the kitchen sink, bathtub and shower.
Toilet water level changes. When you flush the toilet, the water level rises and then goes right down before returning to its normal level.
Gurgling sounds. When you drain the sink, the water makes gurgling sounds.
Smelly drains. If the drains are partially blocked, there’s usually a smell coming from the trapped waste.
Sewer backup. Wastewater and sewage flow back into your drains when someone is showering or the washing machine is draining.
Damp or wet spots in the yard. There are unusual damp areas in yard, and you may notice wastewater collecting on the surface.

Why and How Do Sewer Clogs Happen?

There are many reasons for a sewer line blockage, especially in older homes that use cast iron, steel or ceramic sewer lines. Here are some common reasons sewers clog:

Grease and fatty buildup. Oils and grease from cooking solidify in the sewer and get trapped at bends in the line.
Roots growing into pipes. It’s not uncommon to find plant and tree roots in sewer pipes. They force their way in through pipe joints and damaged piping.
Faulty garbage disposal unit. If your garbage disposal unit is poorly adjusted or faulty, it can let large solids into the drain.
Foreign objects. The disposal of foreign objects like diapers and sanitary products through the toilet is a common cause of sewer clogs.
Broken sewer pipe. Soil movement and subsidence, as well as heavy loads above the pipe, can cause cracked or crushed pipes.
Scale buildup. Limestone scale and rust can partially block steel and cast iron sewer lines.
Main sewer clog. If the municipal sewer line is blocked, sewage can flow back into your sewer line and home.
Septic tank blockage. A blocked septic tank can cause a backflow of sewage into the home.

What Should You Do If You Suspect the Sewer Line Is Clogged?

If you suspect a clogged sewer, stop discharging water down the drain and don’t flush the toilet, as this will only make things worse. Here are some DIY ideas you can try to clear sewer clogs.

Try to Identify the Source of the Problem

Check to see if all your drains are blocked. This should be obvious as the blockage will only affect part of the house. Open the sewer inspection line to check whether it’s clear.

Attempt to Clear the Blockage Using a Toilet Plunger

Try to clear the blockage with a toilet plunger. Run hot water into the sink and place the plunger over the drain. Pull it back sharply to create a vacuum. Repeat several times to see if it clears the blockage.

Pour Boiling Water Down the Drain

Pour boiling water down the drain nearest the blockage. The water may soften the blockage and clear the drain. Alternatively, use a liquid drain cleaner. Be careful to follow the safety instructions on the container.

Use a Drain Snake

Buy a drain snake for sewers from a hardware store. Check that it has a protective sleeve so it doesn’t scratch the toilet bowl. Most drains have U-traps, so be careful to twist the snake around until it gets around the bend; never force it.

How Can You Unclog a Sewer Pipe?

If you can't clear the sewer system, it’s time to call in a professional drain cleaner. They usually perform a sewer inspection and use one or more of the following drain cleaning techniques.

Locate the Blockage

The plumber opens all the inspection points to see if they can find the place where the sewer is blocked. They may use a drain inspection camera to precisely locate where the blockage is situated.

Professional Auger

The most common cleaning technique is to use a long drum or motorized auger to clear the blockage. These have different lengths and a coil spring or blade at the end to cut into the debris. Depending on where the blockage is, the plumber may partially disassemble your drains for better access.

Hydro Jetting Sewer Line

The plumber may decide to use a hydro jet to clear stubborn blockages. The unit has a high-pressure water pump and a long reinforced hose that’s fed into the sewer line. Using a fine nozzle, the unit cuts into the debris and, once broken, pushes it down the line.

Sewer Pipe Repair or Replacement

Occasionally, you may need to replace sections of damaged sewer pipe. Depending on its condition, it may be necessary to replace the complete line. Replacement usually requires excavating the old line, but it’s sometimes possible to reline the pipe in situ.

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

The cost to fix sewer clogs depends on the time it takes to find and clear the blockage. According to HomeGuide, the labor cost to unclog a sink or drain is between $75 and $250 (CAD 106 and CAD 354).

Sewer Video Inspection

Unless the blockage location is easy to pinpoint, the plumber may do a sewer line inspection using a small video camera fitted to a long, flexible cable fed down the sewer line. According to Forbes, the average cost for a sewer line inspection is between $125 and $500 (CAD 177 and CAD 709).

Mechanical Drain Cleaning

Mechanical sewer cleaning costs using a snake or auger to unblock a drain are between $125 and $360 (CAD 177 and CAD 510). If the blockage is severe and affects the main sewer line from the house to the street, the cost may increase to between $500 and $800 (CAD 709 and CAD 1,134).

Hydro Jet Sewer Cleaning

Hydro jetting is best for severe clogs. According to Forbes, the average cost to hydro jet a sewer line is $700 (CAD 992). This could increase to $1,100 (CAD 1,600) for major clogs that are further down the sewer line.

Sewer Line Replacement

If the sewer line is damaged, it may be necessary to replace the sewer line. This Old House estimates that the cost to replace a 40-foot sewer line is $3,320 (CAD 4,706). This figure assumes an average pipe depth of between 18 and 30 inches and a standard 4-inch plastic sewer pipe.

Reline Sewage Pipe

In many instances, it’s possible to reline the sewage pipe. This is more cost-effective than replacement as it doesn’t involve trenching and landscape repairs. The cost for trenchless sewer line replacement, according to This Old House, varies between $60 and $250 (CAD 85 and CAD 354) per linear foot.

All CAD conversions are based on the exchange rate on the date of publication.

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