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Most clogs build up slowly. Hair and soap scum collect in bathroom drains, grease and food scraps coat kitchen lines, and wipes and other products that don't break down catch on joints further along. In older neighbourhoods, tree roots can work their way into the sewer line through cracked or loose joints, and a sagging section of pipe can hold waste instead of letting it flow.
Knowing whether the problem sits in one fixture or in the main line changes everything: a single slow sink is a minor job, while several drains backing up at once can mean sewage in the basement. A clear diagnosis from the start, combined with better habits at the sink and the toilet, helps keep the same clog from coming back.
Signs of a clogged drain or a blocked sewer line
- Water drains slowly from a sink, tub or shower, or pools around your feet while you shower.
- A drain or toilet gurgles or bubbles when water goes down somewhere else in the house.
- A sewer or rotten-egg smell comes back even after cleaning.
- The water in the toilet bowl rises unusually high, or drops, after a flush.
- Water backs up into the tub or the basement floor drain when the washing machine empties or a toilet is flushed.
- Soggy ground or an unusually green strip of lawn appears along the path of the sewer line.
- Small drain flies keep hovering around a sink or floor drain.
Fixture drains vs. the main sewer line: finding where the clog is
Each sink, tub, shower and toilet has its own short drain with a trap that holds water to block sewer gas. These branch lines join larger drains inside the walls and floors, which all empty into the main building drain and then the sewer line that runs under the yard to the municipal sewer or a septic system. A clog in a branch affects one fixture; a clog in the main line affects everything that drains into it, and the lowest openings in the house, usually the basement floor drain or shower, overflow first.
That is why a single slow sink can often be cleared at the trap or with a short cable, while several slow drains, or water coming up in the basement when an upstairs toilet is flushed, call for a plumber with the equipment to reach the main line. If your home has a backwater valve, it usually sits on that main line, and the plumber needs to know where it is before running a cable through.
How professionals clear drains: snaking, hydro-jetting and camera inspection
The right method depends on what the blockage is, where it sits and the condition of the pipe. A good drain technician starts by asking which fixtures are affected and since when, then chooses the least aggressive tool that will do the job.
- A drain snake, or auger, is a flexible cable fed into the pipe to break up or pull out hair, grease and small obstructions in fixture drains.
- A motorized drain machine uses a longer, heavier cable with cutting heads to reach the main line and cut through tree roots and packed debris.
- Hydro-jetting sends high-pressure water through a nozzle that scours grease, scale and sludge off the pipe walls, which can clean a line more thoroughly than a cable.
- A sewer camera on a flexible rod shows the inside of the pipe on a screen, so the plumber can spot roots, cracks, sags, collapsed sections or misaligned joints.
- A locator then traces the camera head from above ground to mark exactly where a repair would have to happen.
- Hydro-jetting isn't suited to every pipe, so old, cracked or fragile lines are usually inspected with a camera first.
What not to pour down drains, and habits that prevent clogs
Many clogs come from what goes down the drain rather than from the pipes themselves. The City of Toronto asks residents to keep fats, oils and cooking grease out of drains because they cool, harden and stick to the inside of pipes, and to keep wipes, hygiene products and other items out of the toilet.
- Scrape grease, fat, sauces and food scraps into the compost or the garbage instead of rinsing them down the sink.
- Flush only toilet paper: wipes of any kind, paper towels, cotton swabs, dental floss and hygiene products belong in the garbage.
- Put a strainer over tub and shower drains to catch hair, and empty it often.
- Take unused medications back to a pharmacy rather than pouring or flushing them away.
- Bring paint, solvents, pesticides, motor oil and antifreeze to a household hazardous waste depot.
- Find your sewer cleanout and keep it accessible, so a plumber can reach the main line without removing a toilet.
Chemical drain cleaners and other quick fixes to avoid
- Harsh chemical drain openers can burn skin and eyes, and they rarely dissolve a solid blockage such as roots, wipes or packed grease.
- When a chemical product fails, the pipe is left full of caustic water that the plumber then has to deal with, so tell them what you used.
- Mixing different drain products can release dangerous fumes.
- Plunging a toilet over and over when the main line is blocked only pushes sewage out of the lowest drain in the house.
- Renting a powerful drain machine without experience can leave a cable stuck in the line or damage an old pipe.
- A clog that returns within weeks points to a deeper problem that needs a camera, not another bottle.
When drain cleaning isn't enough: sewer line repair
Cleaning clears the blockage but can't fix the pipe. If the same line clogs again and again, or the camera shows roots growing through joints, a crack, an offset joint or a low spot where waste settles, the lasting fix is to repair or replace that section. Roots in particular tend to grow back after being cut if the joint they came through is still open.
Depending on the damage and the depth of the pipe, a plumber may replace a section by excavating, or rehabilitate the line from the inside with a trenchless method such as lining where the pipe allows it. Work on the sewer connection usually needs a municipal permit, and part of the line may belong to the city, so ask your municipality where your responsibility ends before any digging starts.
Drain Cleaning: frequently asked questions
How do I know if the main sewer line is clogged?
The telltale sign is more than one drain acting up at the same time, especially when water comes up through the basement floor drain or the lowest toilet or shower while fixtures upstairs are in use. A single slow sink or tub usually points to a clog in that fixture's own drain.
What is hydro-jetting, and is it safe for my pipes?
Hydro-jetting cleans a drain with a jet of high-pressure water that scours grease, sludge and roots off the pipe walls. It works well on sound pipes, but an old, cracked or fragile line can be damaged, so a careful plumber inspects the line with a camera before jetting it.
Why get a camera inspection after drain cleaning?
The camera shows why the clog happened. If the line is clean and intact, changing a few habits may be all you need. If it shows roots, a crack, a sag or a collapsed section, you know the clog will come back and can plan a repair. Many plumbers record the inspection so you can keep the footage, which is useful before buying a home or when filing an insurance claim.
Are flushable wipes safe for the sewer?
No. Municipalities such as the City of Toronto list wipes among the items that should never be flushed, because they don't break down like toilet paper and can snag in your pipes and in city sewers. Put them in the garbage, whatever the package says.
Can tree roots really get into a sewer line?
Yes. Roots are drawn to the moisture in and around sewer pipes and can enter through cracks or loose joints, especially in older clay or cast iron lines. Once inside, they catch paper and grease and form a dense mat. A plumber can cut them out, but the joint usually needs repair to keep them from coming back.
Is a clogged basement floor drain the same as a sewer backup?
Not always. A floor drain can clog on its own with sediment or debris, and water from a leak or the washing machine then pools around it. But if water or sewage is rising out of the floor drain, especially during heavy rain, the problem is in the main line or the municipal sewer: call a plumber and, if you have a backwater valve, make sure it is working.
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Written by the LokalMatch editorial team. Reviewed by Zubair Afzal on September 10, 2026. How we write and check our guides