How Does a Clean Out Drain Work?

The drain waste and vent (DWV) pipes inside a home are connected to one overall system, independent of the supply pipes that bring the water into the home. The clean outs for this drain system provide access if a clog gets past the drains on certain fixtures and blocks the drain pipe.

Importance of Clean Outs

A clog can originate in the drain of one fixture, such as a toilet, and cause another fixture, like a bathtub, to back up because the clog has reached deeper within the main drain to which the toilet and tub drainpipes both connect.  The clean out is an opening on the pipe that provides easier access to reaching and removing the obstruction as opposed to having to go the greater, more complicated route through a fixture's drain.


All clean outs must be accessible.  Local codes usually contain regulations on the installation locations of clean outs, and there are often more than one installed. In addition to other locations mandated by local codes, they are placed in the basement, in crawl spaces, in utility rooms and where the house's main sewer line connects to the septic tank or public sewer.  Inside the house, you will find a clean out at the bottom of the soil stack, which is the vertical pipe that carries the discharge of toilets and similar fixtures, such as sinks.

Using a Clean Out

To go through a clean out to remove an obstruction within the pipe, first remove the clean out's plug using a wrench.  The tool that you will use is either a hand-powered auger or a power auger. Guide the auger's cable into the clean out, and feed the cable through the pipe until it reaches and cuts through the clog.  On a soil stack clean out, you can sometimes substitute a garden hose for the auger and feed it through the clean out to flush out the clog with water.

Plug Removal and Installation

If the clean out plug is too difficult for you to remove with a wrench, apply a few drops of a penetrating oil, such as WD-40, on the plug threads, and try to remove it with a pipe wrench.  Placing a cold chisel on the plug and tapping it with a hammer may also effectively turn a stubborn iron plug. When you install the plug back onto the clean out, prevent it from being difficult to remove the next time by wrapping the plug threads with thread seal tape. 

About the Author

Christopher John has been a freelance journalist since 2003. He has written for regional newspapers such as "The Metro Forum" and the "West Tennessee Examiner." John has a Bachelor of Arts in journalism from Memphis State University.