The essentials in 30 seconds
A sewer cleanout is a capped pipe, usually 3 to 4 inches across, that gives direct access to the pipe carrying all your household wastewater to the public sewer. You will usually find it in the basement near where the main drain leaves the house, outside close to the foundation, or near the property line under a small round lid. If several drains are slow, gurgle or back up into each other, suspect the main line. Stop using water, open the cleanout cap slowly to relieve pressure, and use what comes out to decide whether to call a plumber or the city.
- One slow drain is a fixture clog; several slow drains point to the main line.
- Sewage carries germs: gloves, boots and eye protection before you touch the cap.
- In most places the homeowner looks after the pipe from the house to the property line or cleanout, but rules vary by city.
What a sewer cleanout is and where to find it
Every house connects to the public sewer through one pipe, often called the sewer lateral, side sewer or building sewer. The cleanout is a short vertical branch of that pipe with a removable cap, so a plumber can push a cable or camera into the line without digging. Many homes have more than one: one inside near the base of the main drain stack, one where the drain leaves the building and sometimes one at the property line.
| Place | What it looks like | Tip |
|---|---|---|
| Basement or crawl space | A 3- to 4-inch pipe with a square nut or plastic plug, near where the main drain goes through the wall or floor | Follow the largest drain pipe to the wall |
| Outside, next to the foundation | A capped pipe sticking a few inches out of the ground, often outside a bathroom | Check under bushes, mulch and grass |
| Front yard or near the sidewalk | A round lid about 6 inches across, plastic or metal, sometimes marked "SEWER" | It may be buried under soil or bark |
| Garage or utility room | A plug in the floor or low on a wall | Look behind stored items and water heaters |
| Not found | It may be buried under soil, concrete or carpet, or the house may have none | Check the city sewer map or ask a plumber to locate one |
Some cities publish maps that show cleanouts, and a plumber can locate a buried one with a camera and a pipe locator. If your home has none, installing one makes every future clog quicker to clear. In the UK the nearest equivalents are a rodding eye or an inspection chamber (manhole) on the drain.
Signs of a main sewer line clog vs a single-fixture clog
| What you notice | Single-fixture clog | Main line clog |
|---|---|---|
| Slow drain | One sink, tub or toilet | Several fixtures, often worst on the lowest floor |
| Flushing the toilet | Only the toilet is affected | Water rises or bubbles in the tub, shower or floor drain |
| Washing machine draining | Laundry sink only | Water backs up into a basement floor drain or shower |
| Gurgling | Rare | Gurgling in drains after flushing or draining a sink |
| Smell | Local to that drain | Sewer odor in the basement or from several drains |
| What to do | Plunge or snake that fixture; see how to unblock a sink | Stop using water and go to the cleanout |
If neighbors on the same street have the same problem at the same time, the blockage may be in the public sewer main: call your city's sewer department first.
How to use your sewer cleanout safely
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01
Stop using water
Every flush, shower or load of laundry adds to the backup. Tell everyone in the house and switch off the dishwasher and washer.
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02
Find the cleanout
Use the table above. An outdoor cleanout is usually the safest one to open, because any overflow stays outside.
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03
Prepare
Lay down plastic sheeting and old towels around an indoor cleanout, and keep a bucket ready.
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04
Open the cap slowly
Turn it a little at a time with a wrench, standing to one side. If the line is full, sewage will start to seep around the threads; let the pressure release gradually before you remove the cap completely.
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05
Read the result
If wastewater comes out or stands in the pipe, the blockage is further down the line, between the cleanout and the street. If the pipe is empty and dry, the clog is inside the house, between the fixtures and the cleanout.
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06
Report or call
Water in the cleanout: call your city's sewer department to check the public main, then a drain cleaning company if the main is clear. Dry cleanout: call a plumber to clear the house drain.
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07
Close it properly
Clean the threads and refit the cap firmly so sewer gas stays in the pipe and nothing falls in.
Using a drain auger in the cleanout
A hand auger can clear a soft blockage close to the cleanout. A powered drum auger rented for the day reaches much further, but its cable stores a lot of torque and can whip or kink.
- Feed the cable in until you feel resistance, then let the auger work rather than forcing it.
- Pull back regularly to clear debris from the head.
- Wear leather gloves and eye protection, and keep loose sleeves away from the drum.
- If the cable comes back with fine, hairlike roots, or stops at the same spot every time, book a professional and a camera inspection.
Camera inspections, roots and other jobs for a professional
Most backups in older neighborhoods happen when tree roots grow into a cracked or broken lateral. Older laterals are often clay or cast iron, and roots find their way in at the joints. A drain cleaning service can cut roots out, but they grow back, so the long-term fix may be lining or replacing the damaged section.
Call a licensed plumber or drain cleaning company when:
- the clog returns within weeks of clearing it, or the auger meets roots;
- sewage reaches the basement floor drain or comes up through the cleanout without any water use;
- you notice a soggy patch or a sinkhole in the yard along the line of the pipe;
- the cleanout is missing, broken or buried and needs installing or repairing (many cities require a permit);
- you are buying a house with an older lateral and want to know its condition.
What to ask for:
- A camera inspection (also called televising the lateral) and a copy of the video, before you agree to any repair. It shows roots, cracks, sags and collapsed sections, and where they are.
- The location and depth of any defect, and whether it is on your side of the line or in the public right-of-way.
- The repair options: root cutting and cleaning, lining the old pipe or replacing a section, and the permits each one needs.
- Proof of licensing, especially for any work in the street, where many cities require specially licensed contractors.
Backflow prevention: keeping sewage out of your basement
When heavy rain overloads the public sewer, water can push back up the lateral and out of the lowest drain in your home, usually a basement floor drain. A backwater valve lets wastewater flow out but closes when flow reverses.
| Type | How it works | Upkeep |
|---|---|---|
| Check valve | A flap closes automatically when sewage flows back | Debris can hold it open; FEMA advises inspecting and cleaning it every few years, and some utilities advise twice a year |
| Gate valve | You close it by hand before or during a storm | Better seal, but only protects you when someone closes it; open and close it now and then so it turns freely |
| Dual valve | A check valve plus a manual gate | Suits homes with repeated backups; combines both maintenance routines |
Things to know before you install one:
- A plumbing permit is usually required, and a licensed plumber should choose the type and location.
- The valve is part of your lateral, so it is yours to maintain, not the city's.
- When the valve is closed, water you use inside cannot leave the house. During heavy storms, hold off on flushing, showers, laundry and the dishwasher.
- Disconnect roof downspouts and sump pump discharges from the sewer pipe; some cities, such as Minneapolis, require it.
- Standard homeowner policies often exclude sewer backup. Ask your insurer about a sewer backup endorsement.
Who is responsible for the sewer line: homeowner or city
There is no single national rule. Each city sets its own, usually in its municipal code. The most common arrangements look like this:
| Arrangement | Homeowner looks after | City looks after | Example |
|---|---|---|---|
| Split at the property line | House to the property line | Property line to the main | Indian River County, Florida |
| Split at the property line cleanout | House to the cleanout, including the cleanout | Cleanout to the main | Olympia, Washington, when a cleanout exists at the property line |
| Owner owns the whole lateral | House to the main, including the connection | The public main only | Minneapolis, Minnesota |
In many cities the homeowner must clear blockages anywhere along the lateral, even where the city owns a section, and must show evidence, usually a camera video, that a defect lies in the city's part before the city will repair it. Call your city's sewer or public works department, or check its website, for your local rules, permit requirements and emergency number.
Cleaning up after a sewer backup
- Take photos of the damage before cleaning, then call your insurer.
- Wear gloves, boots, long sleeves and eye protection, and keep children and pets out until the area is clean.
- Remove standing water and sewage as soon as the drain flows, then wash hard surfaces with hot, soapy water and disinfect them.
- Dry the area quickly with fans and a dehumidifier: mold can start within 48 hours. See mold remediation if it does.
- For large or repeated backups, a professional cleanup company is the safer choice.
Sewer cleanout: frequently asked questions
Where is my sewer cleanout?
Usually in the basement near where the main drain leaves the house, outside close to the foundation, or near the property line under a small round lid. A plumber can locate a buried one.
What does a sewer cleanout look like?
A 3- to 4-inch pipe with a threaded cap or plug, sticking out of the floor, wall or ground, or a round lid in the yard sometimes marked "sewer".
How do I know if my main sewer line is clogged?
Several drains are slow at once, water rises in the tub or floor drain when you flush, drains gurgle or you smell sewage in the basement.
Can I clear a main sewer line clog myself?
A soft clog near the cleanout often clears with an auger. Roots, repeated clogs or a collapsed pipe need a professional and a camera inspection.
Is it safe to open a sewer cleanout?
Yes, with gloves, boots and eye protection, and if you loosen the cap slowly while standing to one side to let pressure out gradually.
Who is responsible for the sewer line from the house to the street?
It depends on your city. Most make the homeowner responsible at least from the house to the property line or cleanout; some, up to the public main.
What if my house has no sewer cleanout?
A plumber can install one, usually with a permit. It makes every future clog quicker and simpler to clear.
Sources
City, utility and federal guidance, checked on 27 October 2026.
- City of Minneapolis · Sewer cleanouts ↗What a cleanout is, 4-inch size, basement and yard locations, buried or missing cleanouts, owner responsibility.
- City of Minneapolis · Sewer problems in the home and common questions ↗Signs of a sewer problem, roots in cracked laterals as the main cause of backups, televising the lateral, owner owns the full lateral.
- City of Olympia · Side sewer ownership ↗Property line cleanouts, 6-inch lids marked "SEWER", sewer maps, ownership split at the cleanout, owner clears blockages and proves city defects.
- Indian River County Utilities · The sewer clean out ↗Signs of a main line clog, stopping water use, opening the cap to relieve pressure, reading a full or empty cleanout, split at the property line.
- Madison Metropolitan Sewerage District · Handling sewer backups ↗What to do during a backup, protective gear, asking contractors to televise the lateral, backwater valve upkeep, insurance endorsements, cleanup.
- FEMA · Urban flooding: guidance for homeowners and renters ↗Snaking from the cleanout, clay and cast iron laterals, check, gate and dual backwater valves, permits, water use when valves close, mold within 48 hours.
Several drains slow at once?
Stop using water, find your cleanout and note whether it is full or dry before you call.