If sewage is coming up through a floor drain or a lower-level tub, the cleanout is the pipe to know about — but opening it while the line is backed up can release sewage under pressure. Leave the cap on and call for help.
What it looks like
Most cleanouts are a short length of white PVC or black ABS pipe, three or four inches across, with a screw-on or push-in cap. Older homes may have a cast-iron fitting with a square brass plug.
Some homes have more than one: a main cleanout near where the sewer line leaves the house, and smaller ones on branch lines inside.
Where to look for it
Start where the plumbing leaves the house and work outward.
- Outside, within a few feet of the foundation, usually on the side facing the street or the alley
- In a basement or crawl space, near the floor where the main drain exits
- In a garage, utility room or laundry area on a slab home
- Near the property line, where the home’s line meets the city sewer
What it is used for
A cleanout gives direct access to the line for clearing a blockage with a drain machine or water jetting, and for running a camera to see roots, sags, cracks or buildup.
Without one, the same work often means removing a toilet or going through a roof vent, which takes longer and is harder on the fixtures.
When a home does not have one
Many older homes were built without an accessible cleanout, or have one buried under landscaping. A plumber can add one where the line is reachable, which makes every future drain or sewer visit simpler.