Quick answer
A sewer cleanout is a capped fitting on a drain or sewer pipe, usually a short vertical pipe near the house or in the yard, that lets a plumber open the line to clear clogs and run a camera without pulling a toilet or digging.
Codes require cleanouts at set points in a drain system, such as the upper end of horizontal runs and long straight lengths. Some sewer districts also want an overflow device on the outdoor cleanout.
Quick facts
The key facts about Sewer Cleanout, with sources:
- Purpose
- Access for cleaning and maintenance 2
- Spacing (2015 UPC, WA)
- One for each 100 feet of piping, or fraction thereof 1
- Change of direction
- Extra cleanout past 135° of aggregate horizontal turns 1
- Clearance in front
- 12 inches for pipe 2 inches or less; 18 inches for larger 1
- Overflow device
- Required by Central San (CA) on the private lateral 2
Key takeaways
- A cleanout is the door into your drain system; knowing where it is saves time and money in a backup.
- Codes call for cleanouts at the top of horizontal runs, every 100 feet and after enough turns.
- Older homes may not have an outdoor cleanout at all; one can be added.
- Opening a cleanout on a backed-up line can release sewage under pressure: leave it to a pro.
- In many cities the lateral and its cleanout are the owner’s to maintain.
What a sewer cleanout is and what it looks like
Drain pipes run inside walls, under floors and underground, where no one can reach a clog. A cleanout solves that. It is a fitting with a removable threaded plug or cap, set where a plumber can get a cable, hose or camera into the line.
The one most homeowners mean by "sewer cleanout" is outside. It is a 3-inch or 4-inch pipe sticking a few inches out of the ground near the foundation, or a cap in a small box in the yard, on the main sewer line that runs to the street.
Central San, a California sewer district, says the cleanout gives your plumber easy access for cleaning and maintenance, and notes that an older home may lack one 2.
Inside, you will find smaller cleanouts: a plug at the base of a stack in the basement, a capped tee under a sink, or a cleanout plug on the building drain near where it leaves the house.
How a cleanout is used
- Drain line clogs or backs up
- Plumber finds the nearest cleanout upstream of the clog
- Cap removed, pressure checked
- Drain auger, jetter or camera fed in
- Line cleared, inspected, cap replaced
A cleanout is only useful where it points toward the clog. A two-way cleanout, with openings facing both the house and the street, lets a plumber work in either direction.
The 2015 UPC as adopted in Washington allows a two-way cleanout near the junction of the building drain and building sewer as one of its exceptions 1.
Types of cleanout
| Type | Where | Notes |
|---|---|---|
| Outdoor sewer cleanout | Yard or next to the foundation, on the lateral | The main access for sewer clogs and camera work 2 |
| Two-way cleanout | Where the building drain meets the building sewer | Opens toward the house and toward the street 1 |
| Stack-base cleanout | Bottom of a vertical stack inside | Common in basements |
| Fixture or branch cleanout | Under sinks, behind access panels | For short branch drains |
| Cleanout with overflow device | Outdoor cleanout fitted with a pop-off cap | Lets sewage overflow outside instead of inside; required by Central San 2 |
Example: how many cleanouts a long sewer run needs
A worked example using the 2015 UPC text as adopted in Washington, §707.4 1. The layout is illustrative.
| Run | Rule | Result |
|---|---|---|
| Building drain, upper end | Cleanout at the upper terminal of each horizontal drain 1 | 1 cleanout |
| Sewer run, 230 feet total | One for each 100 feet of piping, or fraction thereof 1 | Up to 3 along the run; ask how your inspector counts the upper-end one |
| Turns totaling 180° | Extra cleanout when aggregate horizontal turns exceed 135° 1 | 1 more cleanout |
| Cleanout on 4-inch pipe | At least 18 inches of clearance in front 1 | Keep it clear |
- 100 ftOne cleanout per 100 feet of run, or fraction§707.4 1
- 135°Aggregate horizontal turns before another cleanout§707.4 1
- 18 inClearance in front, pipe over 2 in§707.9 1
- 30 inHorizontal clearance for underfloor cleanouts from access§707.9 1
Source: [1]
This is model code text from one state’s adoption. Your city may require more, such as a cleanout at the property line, so check before you design or buy.
How to find your sewer cleanout
Walk the outside of the house on the side facing the street or the sewer line. Look for a round cap, often white plastic or black, a few inches above the ground near the foundation, or a small lidded box in the yard or near the sidewalk. It may be hidden by shrubs or mulch.
Inside, look in the basement or crawlspace where the main drain leaves the house, and at the base of vertical stacks. In slab homes, the cleanout may be outside, in a garage, or behind an access panel.
If you cannot find one, a plumber can locate the line with a camera and transmitter. Your home inspection report or a sewer camera inspection may also note where it is. Write the location down and tell everyone in the house.
What a well-placed cleanout saves on a drain call
Accessible cleanout
Missing or buried cleanout
- Plumber may have to pull a toilet or cut in a fitting.
- Longer, messier clog calls.
- Sewage backs up into the lowest drain inside.
- Adding one later means digging.
What a cleanout cannot do
A cleanout gives access; it does not prevent clogs. Roots, grease and broken pipe still cause backups. LA County Public Works says upkeep of the lateral means keeping it clear of roots and grease 3.
A cleanout also does not stop sewage from the public main backing into your home. That takes a backwater valve, a different device.
LA County recommends installing both a backflow preventer and a cleanout on the lateral 3.
And a cleanout far downstream of a clog will not help: the plumber needs one between the house and the blockage.
What drives the cost of cleanout work
We do not print prices, because fair numbers need dated local quotes. Using an existing, accessible cleanout keeps a drain call simpler. Installing a new one is the bigger job.
Cost drivers for a new cleanout: depth of the sewer line; pipe material (cast iron, clay, ABS or PVC); concrete, pavers or landscaping over the line; whether a permit is needed; whether a camera inspection is done at the same time; and whether the line under it needs repair.
See our cost guide and the sewer repair vs. replace tool.
In some cities the lateral work is tied to a sale or remodel.
EBMUD in California requires a private sewer lateral compliance certificate when property is bought or sold, for remodels above a set value, or when the water meter size changes 4.
That can bring a cleanout requirement with it, depending on the city.
How a cleanout is added
The typical order for adding an outdoor cleanout. Details depend on local code and the sewer district.
- Locate the lateral and its depth with a camera and locator.
- Pull a permit where required, and call 811 before digging.
- Excavate to expose the pipe near the foundation.
- Cut in a cleanout fitting, often a two-way type 1.
- Run a riser pipe to grade and fit a cap, or an overflow device where the district requires one 2.
- Inspect, backfill and set a box if the cap is in a lawn or walkway.
- Camera the line through the new cleanout to record its condition.
Keeping your cleanout ready
Warning signs and when to call
- Several drains slow or gurgle at once: a main line problem.
- Water rises in a tub or shower when a toilet flushes.
- Sewage at the lowest floor drain.
- Water or sewage seeping from the outdoor cleanout cap.
- A sewer smell near the cleanout.
Do not open a backed-up cleanout yourself
A cleanout on a full line can blow off and spray sewage.
Sewer gas can also contain hydrogen sulfide; OSHA says it smells like rotten eggs at low levels but deadens your sense of smell at about 100 ppm 5.
Never put your head near or climb into a sewer opening or pit. Wear gloves, keep children away, and let a plumber open it.
For a backup, stop using water and call for drain cleaning or, if sewage is in the house, emergency plumbing.
Code rules and who owns what
Cleanout locations (2015 UPC as amended by Washington, §707.4): each horizontal drainage pipe needs a cleanout at its upper end; each run more than 100 feet long needs one for each 100 feet; and an additional cleanout is required for each aggregate horizontal change of direction over 135 degrees.
A two-way cleanout near the building drain and sewer junction is one listed exception 1.
Clearance (§707.9): 12 inches in front for piping 2 inches or less, 18 inches for larger piping, and 30 inches of horizontal clearance from the access for cleanouts under a floor 1.
Ownership: LA County Public Works says the owner maintains the lateral from the home to the main, including any part under the street 3. Central San says the owner maintains the connection including the connection to the main, and requires an overflow protection device on the private lateral 2.
States on the IPC use different section numbers. Ownership lines vary by city. Rules checked 2026-10-12.
Cleanout vs. related devices
| Device | Job | Main difference |
|---|---|---|
| Sewer cleanout | Access for clearing and inspection 2 | Does not stop backflow |
| Overflow protection device | Pops off so sewage overflows outside 2 | Fits on the outdoor cleanout |
| Backwater valve | Stops sewer backflow into the house | Recommended alongside a cleanout in LA County 3 |
| P-trap | Holds water to block sewer gas at each fixture | At fixtures, not on the main line |
Sewer cleanout myths
- Myth Every house has an outdoor cleanout.
- Reality Central San notes older homes may lack one 2.
- Myth The city maintains the sewer line to my house.
- Reality In LA County the owner maintains the lateral to the main, even under the street 3.
- Myth A cleanout prevents backups.
- Reality It gives access; a backwater valve or overflow device protects the house 32.
- Myth One cleanout is enough for any length.
- Reality The 2015 UPC (WA) calls for one per 100 feet of run 1.
- Myth It is fine to bury the cap under landscaping.
- Reality Code requires working clearance in front of cleanouts 1.
How your sewer district changes cleanout rules
Sewer rules are set locally, and they differ a lot. Central San in Contra Costa County, CA, requires an overflow device on the private lateral 2. EBMUD requires a lateral compliance certificate at sale or major remodel 4.
LA County puts the whole lateral, even under the street, on the owner 3. Call your sewer district or public works department to learn your responsibilities and any cleanout requirements.
When to add or upgrade a cleanout
Add one if your house has no outdoor cleanout and you have had a main-line clog, if you are buying an older home, or if you are already digging for sewer work. Add an overflow cap where your district requires or recommends it.
Next step: find your cleanout today and mark it. If you cannot find one, ask a plumber to locate the line during your next drain call.
Take a photo for the house file
Once you find the cleanout, take a photo with a landmark in frame and note the distance from a corner of the house. In an emergency, anyone can find it fast.
Questions about Sewer Cleanout
Can a sewer cleanout be inside the house?
Yes. Many homes have indoor cleanouts at the base of drain stacks or where the building drain leaves through a basement wall.
The 2015 UPC as adopted in Washington requires at least 12 inches of clear space in front of a cleanout on pipe 2 inches or smaller, and 18 inches on larger pipe.
A cleanout under a floor must be within 30 inches of its access opening.
Where is my sewer cleanout located?
Look outside near the foundation on the side facing the street, or for a lidded box in the yard. Inside, check the basement or crawlspace where the main drain leaves the house and the base of vertical stacks. Some older homes have none.
Do all houses have a sewer cleanout?
No. Central San, a California sewer district, notes that an older home may lack one. Codes for new work require cleanouts at set points, so newer homes usually have them. A plumber can add one to an existing line.
How far apart must cleanouts be?
Under the 2015 UPC as adopted in Washington, each run longer than 100 feet needs a cleanout for each 100 feet, plus one at the upper end of each horizontal drain and an extra one after more than 135 degrees of turns. Your local code may differ.
Can I open my sewer cleanout myself?
You can open a dry, clear line to check it, but do not open one on a backed-up line. Sewage can spray out under pressure, and sewer gas can contain hydrogen sulfide. Let a plumber open a full cleanout.
What is a two-way cleanout?
It is a cleanout with openings facing both upstream toward the house and downstream toward the street. It lets a plumber clear the line in either direction from one spot. Washington’s adopted UPC lists one near the building drain and sewer junction as an allowed option.
Who is responsible for the sewer cleanout?
Usually the property owner. LA County says the owner maintains the lateral from the home to the main, including under the street. Central San says the owner maintains the connection to the main. Check your own city’s rules.
What is a sewer popper or overflow device?
It is a cap on the outdoor cleanout that pops off when the line backs up, so sewage overflows outside instead of inside the house. Central San calls it an overflow protection device and requires one on private laterals.
Why is water coming out of my sewer cleanout?
The line is blocked downstream of the cleanout, often by roots, grease or a broken pipe, or the public main is backed up. Stop using water in the house and call a plumber. If you have an overflow cap, it is doing its job.
Sources
- Washington State Building Code Council, WSR 17-04-089 amending WAC 51-56 (2015 Uniform Plumbing Code), retrieved .
- Central Contra Costa Sanitary District (Central San), Home Guide, retrieved .
- Los Angeles County Public Works, Sewer Maintenance: Homeowner Information, retrieved .
- East Bay Municipal Utility District (EBMUD), Private Sewer Laterals, retrieved .
- U.S. OSHA, Hydrogen Sulfide: Hazards, retrieved .
Expert review
Written by the HyrePlumber Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Cleanout location, spacing, change-of-direction and clearance rules are from 2015 UPC text as amended by Washington (WSR 17-04-089).
Purpose, older-home note, overflow device requirement and ownership from Central San’s Home Guide; lateral ownership and backflow recommendation from LA County Public Works; certificate triggers from EBMUD; hydrogen sulfide figures from OSHA. Example layout is illustrative. Cleanout pipe sizes and locations are general trade description. No prices.
Suggest a correction. We fix errors and say what changed.