What Is a Drain Cleanout, and How Do You Find Yours?

Locating Indoor Drain Cleanouts

1. Follow the Drainage Pipes to the Main Sewage Line

   The drainage pipes inside the home run to every sink, toilet, and water-reliant appliance, like the dishwasher and washing machine, so finding a drainage pipe shouldn't be too difficult. Look for black or white ABS, cast iron, copper, or bronze drainage pipes that lead away from the sink, toilet, or appliance. By following these drainage pipes, you can typically find the main sewage line.

2. Look for a T- or Y-Shaped Pipe Fitting With a Cap or Plug

   When the drain cleanout is installed indoors, it can typically be found on the main sewage line, located just before the main line meets the foundation of the home. The drain cleanout will be on a T- or Y-shaped pipe fitting and it will have a threaded plug with a square nut. It may also have a plastic cap covering this nut.

   However, the drain cleanout isn't always installed on the main line. There are some homes that may have alternate access points to the sewage system, so you will need to look around to find a black or white pipe with a threaded plug and a square nut.

3. Check Bathrooms, Utility Rooms, and the Garage

   If the sewer cleanout is not on the main sewer line, then you will need to inspect alternate locations around the home. Grab a flashlight to help see better in dimly lit areas. The drain cleanout will often be close to a cluster of drainage pipes, like a full bathroom with drains for the sink, toilet, and shower. Inspect each bathroom in the home, looking for a capped black or white ABS plastic drain line.

   If the drain cleanout isn't in the bathrooms, it's a good idea to check the utility room or the garage. In some cases, current or previous owners may have had renovations completed that hid the main drain cleanout. If you suspect that this is the case, it's advised to contact a plumber to help locate the drain cleanout without causing excess damage to the home.

4. Test the Drain Cleanout Plug

   After finding the drain cleanout, it's a good idea to test the plug to help ensure that the plug doesn't become seized from disuse. Put on a pair of disposable gloves and use a pipe wrench or a large pair of channel locks to grip the square nut on the drain cleanout plug. Gradually begin to turn the nut with the wrench, loosening it off fully. Clean away any accumulated grime from the threads, then replace the plug.

   In rare cases, the cleanout may be covered by an expandable plug that is loosened by turning a screw in the center of the plug. Even more rarely, the cleanout fitting may be covered by a rubber bonnet and secured with pipe clamps.

   Warning

   When you start to open the plug and you see water or feel the pressure under the plug, it's time to call a professional. This means the stoppage in the line has filled up the piping that travels outside the house. Once you pull the plug, your drainage pit, yard, or house may fill with backed up raw sewage in that localized area.

Locating Outdoor Drain Cleanouts

1. Walk to the Septic Tank or Municipal Sewer Line

   To find an outdoor drain cleanout, first, you will need to walk to either the septic tank, for properties on a septic system, or to the municipal sewer line. The sewer line is indicated by the nearest manhole or a curb with a large S stamped into the concrete.

2. Estimate the Direction of the Drainage Line

   Septic systems will generally have the drain cleanout located close to the home, in line with the septic tank. Simply walk back from the tank towards the home, looking for a plastic pipe sticking up from the lawn or garden. 

   Similarly, the drain cleanout on a municipal wastewater system will typically be close to the home. It should be in line with the municipal sewer system, but because the actual drainage line is not visible, you will need to trace a broad path through the yard to find the drain cleanout pipe.

   The pipe is usually black or white in color and it's sealed with a threaded plug that has a square nut and may be labeled S, C.O., or cleanout. Though, in some instances, this plug is covered with a plastic cap or a metal lid. With this in mind, search for any objects that could cover or house a 3-, 4-, or 6-inch pipe.

3. Move Lawn Decorations, Foliage, and Other Obstacles

   If you still cannot locate the drain cleanout, then it may be accidentally covered or purposely hidden from sight. The drain cleanout should be close to the home in an area along the main sewer or septic line, which can be indicated by drain pipe clusters in full or partial bathrooms.

   Start moving any lawn decorations that are obscuring the yard outside of bathrooms, expanding the search area as you go. Keep in mind that the cleanout could be buried in a garden or obscured by foliage. Overgrown grass can also be a problem, so you may want to mow the lawn to help make the search easier.

   In some circumstances, the sewer cleanout is completely buried in the yard, in which case you will need to estimate where the drainage line is coming in and use a long screwdriver to penetrate about 1 inch into the ground, probing for the top of the pipe. However, this method is essentially trial and error, even with a good educated guess, so you may want to consider hiring a professional to locate the drain cleanout.

4. Mark and Test the Drain Cleanout

   After locating the drain cleanout, use a metal stake with a brightly colored flag to mark the location, so that you have a quick reference point in case of emergency.

   The drain cleanout plug should also be tested to make sure it can be removed, if necessary. Use a pipe wrench or a set of large channel locks to slowly unscrew the nut from the pipe. The nut should thread out easily, but if you see water or feel pressure in the line, tighten the nut again and call a plumber to clear the clog in the line.