Short definition
A cleanout is a capped access fitting on a drain line that lets a plumber insert a snake, hydro-jet head, or camera without cutting open the pipe. Code requires them at the upper end of every horizontal drain, at the base of every stack, at major changes of direction, and every 100 feet on long runs. In a clog emergency, the cleanout is the first thing a homeowner needs to find.
What it is
A cleanout is a wye or tee fitting with one branch capped by a removable plug — usually brass, ABS, or PVC, with a square head you turn with a wrench. Removing the plug opens a straight or angled shot into the drain line, which is how every modern drain-cleaning method (hand auger, drum machine, jetter, camera) gains access.
The Uniform Plumbing Code (UPC 707) requires a cleanout at the upper terminal of every horizontal drain, at every aggregate change of direction exceeding 135 degrees, and at intervals not exceeding 100 feet on continuous runs. The cleanout must match the drain’s diameter up to 4 inches. In residential work, the typical homeowner-relevant cleanouts are: a fitting at the base of the main stack (often in a basement or crawl space), a wye with a plug just outside the foundation where the building drain becomes the side sewer, and small cleanouts at the upstream end of each branch.
Why it matters to a homeowner
When a drain backs up, your first move is to find a cleanout and relieve pressure — not to start unscrewing a P-trap. A working main cleanout is the difference between a $200 service call and a $2,000 floor cleanup. A two-way cleanout at the property line, often added as part of side-sewer work, lets a plumber rod toward the house or toward the main from a single fitting and is one of the better $200–$600 upgrades during any related job.
If a quote includes “install a two-way cleanout,” that’s not an upcharge — it’s a permanent diagnostic and access improvement. If your home has none of these accessible at all, a plumber may have to pull a toilet to reach the drain, which adds cost and time to every future call.
When you’ll encounter this term
- A sewage backup at a basement floor drain, and you need to find the main cleanout to relieve pressure.
- A sewer-line repair quote includes “two-way cleanout at the property line.”
- An inspector flags a missing cleanout at a change of direction.
- A sewer-camera inspection requires cleanout access; if there’s none, the plumber pulls a toilet instead.
Common variants / not the same as
- Two-way (Kelly) cleanout vs. single-direction. A two-way lets you rod upstream or downstream from one fitting. Almost always installed outside, near the property line.
- Cleanout vs. test tee. A test tee is for plumbing-system pressure tests; a cleanout is for routine snaking.
- Cleanout-to-grade riser vs. flush cap. Many WA building-sewer cleanouts are extended to grade with a flush cap at the property line so they can be opened without digging.
Common failure modes
- Plug rusted or seized in old cast-iron cleanouts — penetrating oil and a long-handled wrench, or sometimes a torch on the brass plug.
- Buried under landscaping or concrete — common with pre-1970 Seattle homes; the original cleanout is somewhere under the basement slab or a flowerbed.
- Backflow during heavy rain — in combined-sewer neighborhoods, a missing or unsecured cap can become an overflow point when the main surcharges.
- Stripped square head — over-tightened over decades; sometimes requires drilling out and replacing the plug.