Can You Cover A Basement Floor Drain?

Whether you’re installing flooring as part of a basement finishing project, protecting your home from the threat of sewage backflow from old city sewer lines, or seeking a solution for nasty sewer smells, you might be wondering whether or not it’s okay to seal that basement floor drain.

Although that hole in the middle of your basement floor does serve an important purpose, you can cover a basement floor drain either permanently with cement or temporarily with a cap or plug.

In this article, we’ll take a look at what purpose a basement floor drain serves, why you may wish to seal it (or not seal it), and what methods, both permanent and temporary, you can use to seal a drain.

Can You Cover A Basement Floor Drain

What Is the Purpose of a Basement Floor Drain?

That unassuming drain in the basement floor may not seem like much, but it plays a critical role in preventing water damage in your home. Perhaps the biggest value for having a floor drain in the basement is flooding.

Being that they are below ground, many basements are susceptible to periodic flooding that can range from a few gallons of water on the floor to a few feet of water. The drain provides a place for the water to go, preventing flooding and protecting appliances, utilities, and furnishings located in the basement.

Many homes have washing machines located in the basement. Should a washing machine drain line clog, the roughly 20 gallons of water the machine uses per load has to go somewhere and that somewhere is typically on the floor. With a basement floor drain, that water will run to the drain and out of the home rather than pool inside the basement.

Water heaters, which hold anywhere from 40 to 120 gallons of water, are typically located in the basement. Should the heater leak or burst, the water can exit through the drain. It’s also useful for getting rid of condensation from an HVAC system or water from a leaky pipe.

A drain also eliminates the need for costly alternatives to removing water from a basement, such as a sump pump.

Can You Cover a Basement Floor Drain?

When most homeowners cover a basement floor drain, it’s usually because they’re finishing the basement space to convert it into a living area. This conversion typically involves laying down some type of flooring.

While it’s possible to lay flooring around a basement floor drain, a visible drain usually detracts from the aesthetics of the finished space. Since most basement floor drains are in the middle of the room, they can be difficult to mask.

There are a variety of reasons why one might want to cover a floor drain. Since it serves as a connection to a septic basin or a city sewer system, a floor drain can often be a means for unpleasant sewer smells to make their way into the home.

While most basement floor drains, like other plumbing receptacles in the home, have a trap that prevents gases from entering the home, these traps often dry out because basement drains are used so infrequently.

There’s also the potential risk of the floor drain becoming a source of flooding in the home. Municipalities with aging water systems can sometimes experience sewage backups from blockages and excessive stormwater. When this happens, city sewage can back up through the drain into a home’s basement.

Since cities are, in most cases, not liable for damage caused by these backups, this can be a good reason for eliminating the floor drain. That said, there is a simple fix for preventing backups through a basement drain that we’ll discuss later.

While covering a floor drain isn’t a good idea for basements prone to flooding during heavy rains, you can cover a basement floor drain using either a cover specially designed to plug this type of drain or good old-fashioned cement.

As cement creates a permanent seal, it’s best suited for basements that never experience flooding from rainwater. It’s also the ideal method for drains that will be covered by some type of flooring.

Caps or plugs are removable and should be used for drains that still need to be accessible. This solution is ideal for basements that may experience occasional flooding.

Keep in mind that a floor drain often functions as a cleanout, which is an access point to remove clogs for toilets, showers, sinks, and other plumbing receptacles in the home. The drains for all of these receptacles meet at your home’s main drain just below the floor drain.

If there is a clog in this line, the basement drain might be the only means for a plumber to access that line to clear the drain with a plumbing snake. While many homes have a cleanout located at the curb where the drain connects to the city’s plumbing system, that isn’t always the case.

If a plumber can’t access your home’s main drain line between the home and the curb to clear a clog, it could require them to dig up the yard to reach a clog, which is very costly. Check to make sure there is another means for accessing the drain line between your home and the city sewer lines before sealing a basement drain.

Where Does a Basement Floor Drain Go?

Basement sump pump

Basement floor drains should be located at the lowest point in the basement. Most basements floor drains are in the middle of the basement, with the floor around it having a slight slope that causes water to drain toward it.

A floor drain leads to a sump pit, a city sewer, or a sewer pit. The water will go to a sump pit if your home’s plumbing is on a septic system. For those on city water, the drain leads to the city’s sewer system. If the basement is below the main sewer line that leaves home, then the water will head to a sewer pit, which has a pump that pumps the water up to the sewer line.

What Options Are There for Covering a Floor Drain?

There are two main options for covering a basement floor drain: cement or a lid or cap. While a permanent option may be the way to go when finishing a basement, a temporary cap or lid is ideal in other situations.

Sealing the Drain

As we discussed above, using cement to seal a floor drain is the best option for those converting their basement into a finished living space by adding carpeting, hardwood, tiles, or some other type of flooring.

This method prevents the threat of backflowing sewage that can easily ruin flooring and any type of furnishings in the space. Remember, however, that cement is not a good idea for basements that are prone to flooding as it eliminates a means for removing the water from the basement.

If you wish to seal a floor drain using cement, it’s best to use hydraulic cement, which is used to stop leaks in concrete and masonry. This will ensure the seal holds up to any backflow pressure from the water being push back against it.

Begin by removing the drain’s grate and clean away any debris from the opening. You’ll only want to seal the first 6 inches or so of the drain.

To prevent cement from falling further into the pipe and potentially causing problems with the home’s main drain, tightly stuff the drain with crumpled newspaper. This will give the cement something solid to rest on while it sets. Once the drain hold is filed, even the top of the floor.

If you’re sealing the drain to prep space for flooring, consider using a floor leveler to level the floor.

Attaching a Lid or Cap

While ceiling a floor drain may be the only option to truly finish a basement space, adding a lid or cap is a good solution to block gasses or prevent backflows.

These caps or plugs are removable, allowing the user to keep the drain closed when no needed or open it in the event of an emergency. Lids and caps come in three different options: test balls, twist plugs, and pressure plugs.

Test Balls

Test balls are used to pressure test plumbing systems; however, they also serve as an effective means for sealing a basement drain. They consist of a rubber bulbous end that resembles an oblong ball and a plastic cap. To use, insert the rubber end into the drain, then inflate the plug with air to the required PSI level. This type of plug is ideal for older drains that may not fit a standard size.

Once inflated, the ball will not allow air or water to pass through either direction, creating an effective seal. While this will plug a drain, test balls are rather conspicuous as the caps stick out several inches from the top of the plug.

Twist Plugs

Twist plugs consist of a metal or plastic cap with a rubber flange that fits inside the drain pipe. Once inserted, the user tightens a wing nut that creates an airtight and watertight seal between the drainpipe and plug. These plugs are easy to use, come in various sizes, and are less conspicuous than other types of drain plugs.

Pressure Plugs

A pressure plug is similar in shape and design to a standard bathtub plug or even a wine cork. The plug tapers from a larger diameter end that is larger than the hole to a narrower end that is smaller than the hole. To use, stick the narrow end in the hole and apply pressure to keep the plug in place.

While pressure plugs create an airtight seal that is ideal for preventing gases from passing through the hole, they may not be strong enough to prevent sewage backflow from pushing it out.

When tightly forced into place, they can also be difficult to remove if you need to access or open the drain line.


For newer homes that use PVC pipes for the plumbing, a threaded plug may be an option. This plug has threads that allow you to screw it into the drain threads, creating a watertight and airtight seal.

To ensure a tight seal, applying plumbers tape to the threads and tighten the plug using a crescent wrench. While these types of plugs create a strong seal that can’t be popped out by backflows, they’ll only work with compatible PVC drains.

Basement Floor Drain Cover Replacement

Oatey 33403 4-in. End of Pipe Gripper Mechanical Plug with Galvanized Screw and Wing Nut, 4 Inch, Red1. Oatey 33403 Plastic Plug – A simple to use design and sturdy construction make this plug a great option for sealing your basement floor. With its 4-inch diameter, this plug will fit the most common basement drains. It has durable plastic construction that will hold up to pressure.

2. Maintaining a tight seal is key when trying to keep outgasses or prevent backflow from entering the basement. A large wing nut makes it easy to tighten the plug to keep it in place while preventing overtightening that can damage the plug or drain, and its thick rubber gasket creates a tight watertight and air-tight seal.

3. Oatey’s plastic plug works on both metal and PVC pipes.

DANCO PlugAll Mechanical Test, Seal & Cleanout Pipe Plug | For Drains & Clean-outs | Fits 1-1/2 inch and 2 inch pipes | DWV Testing (10839),Red4. Danco PlugAll Mechanical Test, Seal & Cleanout Pipe Plug – A sturdy and easy-to-use design makes this plug from Danco one of the best options for sealing a basement drain. The plug is made from durable high-grade plastic, so it won’t break or crack easily. Its long body has two different diameters that make it suitable for 1-1/2-inch and 2-inch drain pipes.

5. Once in place, turn the large plastic knob until tight to create an airtight and watertight seal between its thick rubber gaskets and the pipe.

6. With no tools required, this plug is easy to install or to quickly remove in the event of an emergency. This plug will work with threaded or unthreaded pipes.

How Do I Prevent My Floor Drain From Backing Up?

While sealing the floor drain is one way of ensuring sewage does not back up into your basement in the event, there are other solutions.

The best way to prevent your floor drain from backing up is by using a cheap and easy-to-install backwater valve. A backwater valve consists of a drain with a ball that rests inside of it. When things are flowing the way they should, in one direction from home to city sewer lines, the ball remains out of the way, allowing water to pass through.

When sewage begins to back up from the curbs to your home, it causes the ball to float and seal the drain hole, preventing sewage from backflowing into the basement.

Since backwater valves and floor drains with integrated backwater valves are available for drains of all sizes and are generally easy to install, they are a great solution for those considering sealing their drains to prevent backflow.

Why Is There a Sewage Smell in My Basement?

Although basement drains can often be the source of sewage smells, it’s typically not the fault of the drain but rather the drain’s trap.

A sewer drain leads to a pipe that connects to the city’s sewer system or your septic system. In either case, it creates a means for unpleasant sewage odors to make their way into the basement.

However, like the sinks, toilets, and tubs in the home, basement drains come equipped with traps. This J-shaped piping holds water in it at all times, serving as a vapor barrier that prevents sewer smells from entering the home.

Since basement drains can sit idle with no use for long periods, the water in that trap eventually evaporates, allowing air to pass.

To prevent this, simply add a pitcher of water to the drain once a week. To slow the time it takes for the water in the trap to evaporate, simply add a little cooking oil after dumping water into the trap. The oil will sit on top of the water, creating a seal that prevents the air from reaching the water in the trap and evaporating it.


While basement floor drains can be invaluable plumbing receptacles to prevent your basement from flooding, in certain situations, it may be necessary to seal them. Sewage gases, backflows from overwhelmed city sewer systems, and basement remodels are all good reasons for considering closing up that hole in the floor.

Fortunately, there are both temporary and permanent solutions for sealing a basement drain. Remember, before sealing a basement drain, it’s important to consider whether that drain is a necessary part of protecting your home from flooding or not. Only permanently seal a drain to basements that never flood.

Written By: Yevgen

YevgenI'm a DIY nut, and the founder and chief editor here at Weekend Builds.
This site is a result of my DIY passion, and to share the joys I have experienced fixing, building, and creating things over the years.

Leave a Comment