What Is a Sewer Cleanout? How to Find Yours at Home

However, the drain cleanout isn’t always installed on the main line. Some homes may have alternate access points to the sewage system, so look around for a black or white pipe with a threaded plug and a square nut. The drain cleanout might 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.

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

Make sure you know where the sewer cleanout is located in case of emergencies.

Timothy Dale is a home repair expert and writer with over a decade of hands-on construction and home improvement experience. He is skilled in residential, commercial, industrial and institutional plumbing, electrical, carpentry, installation, renovations, and project management.

Richard Epstein is a licensed master plumber with over 40 years experience in residential and commercial plumbing. He specializes in estimating as well as design and engineering for plumbing systems, and he works for one of New York’s largest union plumbing construction companies.

• Working Time: 10 mins – 2 hrs
• Total Time: 10 mins – 2 hrs

• Skill Level: Beginner

The drain cleanout is a direct access point to the main sewer line inside or outside of the home. It can also be referred to as the main house trap when it is located inside the home or the sewer cleanout when it’s located outside the home.

Despite the slight difference in terms, the function of this cleanout remains the same: This addition to the home plumbing system is intended to give plumbing professionals an easy-to-access point through which they can reach clogs and sewage backup in the main sewage line that extends from the foundation of the home, under the ground, and out to the municipal sewage system, a private septic tank, or the portion of main house drain piping downstream of the house trap.

Only plumbing professionals should use the drain cleanout, but knowing the location of this access point can save time during an emergency clog or backup, potentially saving thousands in cleaning and restoration. Plumbing companies may also charge less for their services if the plumber doesn’t need to worry about locating the drain cleanout.

A drain cleanout pipe is 3, 4, or 6 inches in diameter and typically white or black in color. It has become common practice for the sewage line, drain cleanout, plug, and cap to be made of ABS plastic, though there are about 76 million homes in America that still have cast iron sewage lines with brass or cast iron drain cleanouts. Some homes may also have brass or copper drainage lines, though these are much rarer. Keep your sewer line material in mind while you follow these simple steps to search for the main drain or plumbing cleanout.

Before You Begin

Before beginning, it’s important to note that the general location of the drain cleanout is different depending on the local climate.

• Standard homes in colder climates will typically have drain cleanouts located inside the home.
• Homes in colder climates that were built on a slab foundation may have an outdoor drain cleanout, or it can be located in a bathroom, garage, or utility room, so individuals with this type of home may need to search both indoors and outdoors.
• Homes in warmer climates will usually have an outdoor drain cleanout located in the yard.

What You’ll Need

Equipment / Tools

• Flashlight
• Pipe wrench
• Screwdriver

Materials

Instructions

Locating Indoor Drain Cleanouts

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.

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.

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.

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

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.

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.

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.

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.

Warning

Even experienced DIYers can cause significant damage to the home sewage system. This can lead to sewage backing up into the septic system, the yard, or even into the home. Save time, effort, and potentially thousands of dollars in clean-up and home restoration fees by only employing licensed professional plumbers to clear clogs and make repairs to the main drainage line and drain cleanout.

What Is a Sewer Cleanout? How to Find Yours at Home

Aaron Stickley is a licensed plumber with 15 years of experience in commercial, new residential plumbing, and residential service and repair. He started his own residential service and repair plumbing business. Aaron’s articles about plumbing on The Spruce span four years.

Richard Epstein is a licensed master plumber with over 40 years experience in residential and commercial plumbing. He specializes in estimating as well as design and engineering for plumbing systems, and he works for one of New York’s largest union plumbing construction companies.

When your home’s drain to the main sewer line gets clogged, your sewer cleanout likely needs unclogging. It’s a capped pipe that plumbers use to remove clogs. Most—but not all—homes have a sewer cleanout. Some cleanouts are outside the front door, but others can be near a septic tank or indoors. The cleanout is sometimes called the main house trap when it’s located inside the house.

When a main drain clog happens, raw sewage can back up into your entire house, causing a disaster. Until the clog is removed, no drains in your plumbing fixtures can be safely used. It is an unpleasant and potentially costly problem. Here’s what you need to know about cleanouts, how to find them, and how they’re unclogged.

What Is a Sewer Cleanout?

A sewer cleanout is an access point for a plumber to address a problem in a home’s main plumbing line to the sewer system. Clearing a main sewer line stoppage is best approached from this fitting. This line connects the home plumbing system with the main sewage line that extends from the home’s foundation, under the ground, and out to the municipal sewage system or a private septic tank.

A plumber can thread a camera from the cleanout access point and determine where a clog is occurring and what’s causing the blockage. A drain snake or motorized auger can dislodge any clogs in the main sewer line to restore the home’s drain system to proper function.

Sewer lines from the home to the main sewer line will be white PVC plastic pipe in newer homes or black cast iron pipe in older homes. If an older home has a cleanout, it will likely have a brass or cast iron drain cleanout.

What Does a Sewer Cleanout Look Like?

A drain cleanout pipe is 3, 4, or 6 inches in diameter and typically white or black. It has become common practice for the sewage line, drain cleanout, plug, and cap to be made of ABS plastic, though about 76 million homes in America still have cast iron sewage lines with brass or cast iron drain cleanouts. Those homes may also have brass or copper drainage lines, though they are becoming much rarer.

Outdoors, they are usually sealed with a threaded plug with a square nut and may be labeled S, C.O., or cleanout. However, this plug is sometimes 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.

Indoors, the drain cleanout will be on a T- or Y-shaped pipe fitting, with a threaded plug with a square nut. It may also have a plastic cap covering this nut.

How Do I Find My Main Cleanout?

The main cleanout for your home may be outdoors in the yard, in a bathroom or utility area, or in the basement. Finding the cleanout depends on the house style and your geographic climate. Only plumbing professionals should use the drain cleanout, but knowing the location of this access point can save time during an emergency clog or backup, potentially saving thousands in cleaning and restoration.

Plumbing companies may also charge less if the plumber doesn’t need to worry about locating the drain cleanout. Here are some tips for finding your cleanout.

Prime Locations for the Sewer Cleanout

Outdoors

In warm climates with homes on slab foundations, the main cleanout fitting is often outside, usually near the home’s exterior walls. Look behind bushes or a metal or plastic box recessed into the ground.

The easiest way to locate the sewer cleanout is to walk backward from the main sewer line (nearest maintenance hole or a curb with a large S stamped into the concrete) or your home’s septic system. Follow the line from there; it’s usually located next to the house in line with the septic tank or municipal sewer system. Look for a plastic pipe sticking up from the lawn or garden.

The main cleanout fitting is usually a large-diameter pipe with one or two threaded plugs in the top. It may extend above the ground near an outside wall or inside a ground box covered by a metal cover.

If you still cannot locate the drain cleanout, it may be accidentally covered or purposely hidden by being buried in a garden or obscured by foliage. Move lawn decorations obscuring the yard outside bathrooms, expanding the search area as you go. Overgrown grass can also be a problem, so you may want to mow the lawn to help make the search easier.

If the sewer cleanout is completely buried in the yard, 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 consider hiring a professional to locate the drain cleanout.

Bathrooms or Utility Areas

In other homes with slab foundations, the main drain may be located in a bathroom, usually on the floor near the toilet, or in a garage or utility area, usually near a floor drain. In these locations, the threaded plug may be flush-mounted into the floor or threaded into a short length of large-diameter pipe extending up from the floor. It can usually be opened with a large pipe wrench.

To locate the cleanout, follow the drainage pipes inside the house. It can typically be found on the main sewage line, just before it meets the home’s foundation. The drain cleanout will be on a T- or Y-shaped pipe fitting, with 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. Some homes may have alternate access points to the sewage system, so look around for a black or white pipe with a threaded plug and a square nut. The drain cleanout might 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, checking the utility room or the garage is a good idea. In some cases, current or previous owners may have completed renovations that hid the main drain cleanout. If you suspect this is the case, contact a plumber to help locate the drain cleanout without causing excess damage to the home.

Tip

If the cleanout cap is difficult to unscrew, it may have to be chopped out by a hammer and chisel and replaced with a fit-all plug. This universal plug has a lead ring hammered on to make a seal.

Basements

In houses in colder climates, where basements are more common, the main cleanout is usually found on the basement floor, usually near the foundation wall. A threaded plug will fit into a short length of large-diameter pipe that extends up from the floor.

To find the cleanout, follow a direct line from the vertical soil stack to the foundation wall, following the shortest path. The main cleanout will likely be located along this line. If not this fitting, there may be a Y-fitting at the bottom of the main drain soil stack, where it disappears under the concrete slab.

In larger homes, there may be two or even three cleanout fittings, one for each main drain pipe running from separate soil stacks to the street.

Tip

When opening a cleanout, have a bucket handy if backed-up sewage starts flowing out of the cleanout. It can help you avoid a mess in your home or yard.

Mark and Test the Cleanout

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

The drain cleanout plug should also be tested to ensure it can be removed if necessary. Use a pipe wrench or a set of large channel locks to unscrew the nut from the pipe slowly. 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.

When you find a drain cleanout indoors, also test the plug to help ensure that the plug doesn’t become seized from disuse. Put on 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 turn the nut with the wrench, loosening it off thoroughly. Clean away any accumulated grime from the threads, then replace the plug.

In rare cases, the cleanout may be covered by an expandable plug loosened by turning a screw in the plug’s center. 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 see water or feel the pressure under it, 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.

How to Maintain Your Drain Lines

Most plumbers can do main drain line cleaning, but there are also companies specializing in this work. An annual inspection and cleaning by a sewer specialist is a good idea, especially if you have a landscape with large trees. Tree roots can easily penetrate sewer lines. Routine sewer drain line cleaning may prevent a disastrous blockage.

Cleaning the main drain blockage can be done by a homeowner, but it may require special tools, such as a motorized drain auger available for rental at tool centers and major home improvement stores. Generally, it is not recommended for non-professionals to attempt cleaning the line.

Warning

Even experienced DIYers can cause significant damage to the home sewage system. This can lead to sewage backing up into the septic system, the yard, or the home. Save time, effort, and potentially thousands of dollars in clean-up and home restoration fees by employing only licensed professionals to clear clogs and repair the main drainage line and drain cleanout.

Professionals unclog cleanouts using cameras to identify clogs and determine the right tool for the job, ranging from a drain auger to a powerful water jet.

Signs a sewer cleanout is clogged include toilet drainage backing up into sinks, tubs, and showers; discolored, smelly water; or persistent, unexplainable wet areas on your lawn.

Older homes may not have a cleanout; they became standard in building codes during the 1940s. If your home does not have a cleanout, the best way to unclog a line going to the sewer is with a plumbing snake. If your plumbing uses a network of old cast iron pipes, consider updating it to PVC to save yourself from a headache down the line.