Basement Floor Drain Backing Up? Here’s How to Fix It

There are few things more unpleasant for a homeowner to deal with than backed-up sewage on the basement floor. This foul-smelling problem must be addressed immediately, but that doesn’t mean it has to cost you a lot of money.

While hiring a plumber to fix a clogged basement floor drain is the easy way out, it will cost you between $200 and $500. Given that basement drains often present a more complex clog removal than sink, toilet, or bath clogs, that price is typically on the high end. But don’t open up that checkbook just yet. There are plenty of ways to clear that clog without forking over all that money for a plumber.

In this article, we’ll review methods for clearing clogged basement drains, what causes these types of clogs to begin with, and what steps you can take to prevent future clogs once the current problem is fixed. Basement floor drain backing up? Here’s how to fix It.

Basement Floor Drain Backing Up

The Purpose of Basement Floor Drains

Floor drains play an important role in keeping your house dry. As the lowest drain in the home, they serve as egress for stormwater that may seep or gush into your basement during heavy rains or when a washing machine or water heater leaks.

Most basement floor drains are in the middle of the basement floor, sloped toward the drain so that any water that enters the basement is channeled to it.

As with other plumbing fixtures in the house, once water enters the drain, it goes through a P trap that serves as a vapor barrier to prevent sewer odors from entering the home before traveling down a drainpipe that leads to either a city sewer or a home’s septic system.

Floor drains also have cleanouts located just under the grate that bypasses the trap, allowing you or a plumber to access the line in the event of a clog. A cleanout typically has a cap on it that is removed for servicing.

Some floor drains have valves that prevent water from backflowing into the basement if the city sewer system backs up.

Symptoms of Basement Drain Line Problems

It’s important to understand that all the toilet, sink, and tubs drain in the home run to this main drain line. When there’s a clog in this line, the water and waste from these drains backflow out of the lowest exit, which is the basement drain.

Slow Draining

If you’re your bathtub starts filling up during a shower or your sink begins to fill while brushing your teeth, then you’re dealing with a slow drain problem. Slow drains are typically caused by a buildup of hair and soap in bathrooms, grease and fat from the kitchen sink or wads of toilet paper in the toilet.

All of this material ends up flowing through your home’s main drain. Although a home’s 4-inch main sewer pipe is twice as wide as the 1-1/2- or 2-inch drains that run throughout the home at 4 inches in diameter, it must handle a greater flow of liquids and solids, making it susceptible to clogs.

A slow drain in a single sink, toilet or shower, likely indicates a clog in that particular receptacle’s 2-inch drain pipe. However, if all the drains in a home are slow, it’s a good indication that the basement sewer line is clogged.

Foul Odors

A foul odor in the basement is another indication that something is wrong with the basement drain line. A sewer smell means that the line backs up, causing sewer water to backflow into the basement. If it’s a slow drain as opposed to a completely clogged one, this water may back up into the basement, then drain without you knowing it.

In this case, the telltale sign will be the smell that the sewage water leaves behind. Keep in mind that foul odors are also signs of a much easier problem to fix–a dry basement drain trap.

If you’re not sure which, run some water into the basement drain. Adding water to a dry trap should take care of the odors by refilling the trap. If the odors persist, you may have a clog.

Air Bubbles Coming From Drains and Toilets

Yet another sign of a clogged basement drain line is bubbles in the toilet or drains. These bubbles are created by negative air pressure caused by a clog. Instead of the air flowing through the line with water and waste, it’s hitting a clog, causing the air to go back through the lines, creating these bubbles.

This could mean that the main drain line is clogged, the toilet drain is clogged, or the vent stack for your home’s plumbing, located on the roof, has something blocking it. If you have this problem in more than one plumbing fixture and the vent stack is fine, then the culprit is probably a clog in the main sewer line.

Water Is Backing When:

  • Washing Clothes (Washer Drains). A washing machine is a great indicator of a clog in the main drain line, especially if it’s located in the basement.
    When a washing machine drains, it rapidly releases 20 to 30 gallons of water into your home’s main drain. Even a moderate clog will likely cause a backflow, sending water out of the drain and onto the basement floor.
  • When Toilet Is Flushed. Although today’s toilets use about a quarter of the water older toilets do, putting much less pressure on the main sewer line per flush, they still can exacerbate a clog in the line since they carry solid waste with them.
  • When Kitchen Sink Drains. When you pull the plug on a kitchen sink full of water, it sends about 32 liters of water through the drain, putting pressure on that 4-inch line. If water backs up when the sink drains, it’s a good indication of a clog.
  • When It Rains. Water backflowing into the basement through the drain may not be a problem you can fix because it may not be your problem. Some municipalities in the U.S. are dealing with the consequences of decades of not upgrading their sewer systems.Many city sewers are crumbling as old pipes erode and tree roots work their way into the system. Heavy rains put more pressure on these sewer systems to deal with stormwater as well as wastewater. This can cause these lines to clog and backflow into homes.If sewage is backing up into your basement when it rains, this could be the problem. If the problem is with the city sewer system, you’re likely no alone. Check with your neighbors to see if they’re experiencing the same problem when it rains.
  • After Shower. The average shower lasts about 8 minutes and uses about 17 gallons of water. That’s a lot of water for your main drain to handle. If there’s an obstruction in the mainline, a shower will cause soapy water to back up into the basement.

Sewage Coming Out of Cleanout Pipe

A cleanout pipe is a capped pipe that gives you or the plumber access to the drain line for maintenance and clear clogs. These cleanouts are usually located in the basement on an exposed section of line.

While these lines typically have a removable cap on them, sewage water can breach this cap if the lines are backing up. If sewage flows out of the cleanout pipe, you likely have a sewage backup in the main line.

Why Is My Basement Floor Drain Backing Up?


Main Sewer Line Clogged

  • Buildup From Grease. Grease is not water-soluble and sticky, so it makes sense that it doesn’t travel through drain lines well. Over time, grease will adhere to the insides of the main sewer line, slowly accumulating and closing off the pipe.To prevent this from happening, avoid dumping large quantities of grease down the drain. You can also dump boiling water down the drain once a month to remove any grease collecting on the pipes.
  • Rust. Older homes with galvanized drain pipes are prone to rusting over time. Rust can grow inside the pipe, eventually closing it off.While there are temporary ways to fix a rusty pipe, it will eventually need to be replaced with PVC, which, unfortunately, means a costly upgrade that is best left to the pros.
  • Improperly Flushed Items. Paper towels, baby wipes, wads of toilet paper, cotton swabs, toys, and a whole host of other materials that one can flush down a toilet can get caught in the main sewer drain, leading to a clog.Practice good flushing habits by only putting toilet paper in the toilet and not stuffing the can with too much of it before flushing.
  • Debris, Hair & Dirt. Humans shed between 50 and 100 hairs each day, with much of that shedding taking place in the shower. This means that a lot of hair runs into your home’s drains.While shorter hairs may pass easily, longer hairs can become entangled with other dirt and debris passing through the main sewer line, creating a clog. If this is a persistent problem. Consider installing a drain cover in your showers that will catch hair before it enters your home’s main sewer line.
  • Crystallization. materials such as sand, lint, soap scum, and urine can crystallize inside the long drain pipe that runs from the home to the curb over time, creating clogs.

Sewer Line Damage

Sometimes the damage to a basement line has nothing to do with how the system is used. Outside forces can damage lines and some plumbing just eventually wears out.

Unfortunately, A broken line must be dug, up, replaced, and repaired, which means digging through the basement floor or digging through the yard, depending on where the break is. This is a costly and complicated repair best left to the pros.

  • Separation Between Main Drain Line and Basement Pipe. A broken drain line is perhaps the worst-case scenario when it comes to the causes of a backed-up basement drain. If the basement pipe and main drain break apart, you’ll need to hire a plumber to repair them.
  • Deteriorated Pipes. As with many parts of a home, pipes eventually wear out. While PVC pipes will last many, many years, galvanized pipes in older homes will eventually succumb to rust, requiring replacement.
  • Tree Roots. A tree’s roots can grow into and damage the concrete foundation of a home, so it should come as little surprise that a tree can also grow into a home’s main sewer line.While a power auger can drill through the root to create an opening in the line to create a temporary fix, it will need to be replaced once a root has grown through it.
  • Freezing Temps. Unlike water supply lines that constantly hold water and are therefore susceptible to freezing and bursting, drains lines typically don’t freeze as they only hold water that is flowing and are empty when not in use.Drain pipes are usually below the freeze line. That said, unseasonably extreme cold can cause the normal frost line in the ground to descend to the pipe, freezing any water sitting in it. Over time, this can accumulate, eventually damaging the pipe.

Basement Drain Clogged

Sometimes a backed-up basement drain has nothing to do with the main sewer line. It could mean that the basement drain is clogged. The P trap that prevents sewer gasses from entering the home through the basement drain is an ideal place for clogs to occur because of the tight bends in the pipe (hence its name.)

This P-shape creates an ideal place for debris to collect and clog. Clearing this clog with a simple plumbing snake may be all you need to get eliminate backflows. If this is the problem, the backflowing will only occur when water is dumped directly into the basement drain. There should be no clogging when using other plumbing fixtures in the home.

Clogged Vent Pipe


Ever wonder what all of those pipes sticking out of the roof of your home are for? One of them is a vent for your home’s plumbing system. It helps to regulate the air pressure in the plumbing system to keep things flowing while at the same time allowing odors to escape.

Unfortunately, these pipes also make an ideal nesting spot for birds, which can close off this vent, throwing the air pressure in the home out of whack and resulting in slow drainage and bubbles in drains and toilets. If the main sewer drain isn’t the problem, climb on the roof and check the vent pipe.

Too Much Water Drained

Sometimes the problem is simply too much water for the drain to handle. Most main sewer pipes are 4 inches in diameter and can handle more than 160 gallons per minute, which is much more than a home can produce even when a full washing machine is emptying and several water faucets are open.

Other factors can decrease that capacity, such as older pipes with narrower diameters, partial clogs, and build-up, all of which can decrease the pipe’s flow rate and cause backflow when too much water is drained at one time.

What to Do if Basement Drain Backs Up?

Now that you’ve determined there is a problem with water backing up in the basement drain; it’s time to attack the problem. But how? There are several approaches that range from a plunger and a can of Coca-Cola to hauling in heavy machinery.

When addressing the problem, it’s best, to begin with, the simplest approach and work your way up the ladder. In this section, we’ll guide you through how to safely and effectively handle a basement drain that’s backing up.

Step 1. Take the Proper Safety Precautions

If you have standing water in the basement, begin by taking the proper safety precautions. There are live power lines running through the entirety of a home, making standing water a significant electrical shock hazard. Begin by shutting off power to the basement at the circuit breaker box.

Since backed-up sewer water could very well contain pathogens and bacteria, protect yourself by wearing gloves, goggles, and a face mask.

Step 2. Remove Standing Water

If the backup is severe enough that you have a significant amount of standing water on the floor, you’ll need to get rid of that water before you can address the clogged drain.

First, make sure that the water level stops rising by shutting off your home’s water main. Remember, if the main drain is clogged, any running faucets or flushed toilets will add to the problem. You won’t be able to use any of the home’s water until the issue is resolved.

Use a portable pump with a hose that can run through a basement window to pump the water out of the basement. If finding a way to remove the water from the basement is difficult, you can try plunging the drain out to see if you can get the drain working again.

Step 3. Clean the Trap.

Once the water has subsided and you can access the drain, start by cleaning out the drain’s P-trap. Remove the grate cover and pry out the backflow preventer if there is one. Use a wet-dry vac or a short plumbing snake to clear out the P trap. If the clog is in the P trap, this will solve the problem.

If the clog still exists, locate the cleanout plug and remove it with a pipe wrench or crescent wrench to access the drain line.

Step 4. Using Chemicals and a Plunger

The methods below start with easy and affordable solutions before bringing in the big guns for stubborn clogs.


Luigi's Sink and Drain Plunger for Bathrooms, Kitchens, Sinks, Baths and Showers. Small and Powerful, Commercial Style 'Plumbers Plunger' with Large BellowsA drain plunger removes clogs by creating suction that puts pressure on the clog, dislodging it and pushing it through the pipe. Plungers will work for minor clogs caused by wads of toilet paper or objects that may be clogging the drain.

For a plunger to work, you must create an air-tight seal around the drain. You might consider adding enough water to create a small pool around the drain that will allow you to place the lip of the plunger underwater and around the drain to achieve that seal.

Plunge the drain by pushing the handle in and out until the clog is removed. Keep in mind that this will only work for minor clogs. Since most main drains are 4 inches in diameter, the plunger may not produce enough force to dislodge the material clogging this large space.

2. Baking Soda & Vinegar

This simple home remedy is a great option for removing mild clogs if you don’t have a plunger on hand. Begin by letting hot water run into the pipes. Drop 1/2-cup of baking soda down the drain, followed by a cup of vinegar. Seal the drain and wait for 10 minutes.

The fizzing reaction that occurs when the two combine is vigorous enough that it can break apart clogs. After the solution has had time to work its magic, pour hot water down the drain.

3. Coca-cola

Although it may seem strange given that it’s a beverage, Coca-Cola is loaded with phosphoric acid, which is perfect for breaking down buildup in a clogged drain. You’ll have to give it some time though.

To use this method, dump an entire 2-liter bottle into the drain, then allow it to sit for at least an hour to give it time to work through the clog. Then flush with boiling water.

4. Drano

Drano Max Gel Drain Clog Remover and Cleaner for Shower or Sink Drains, Unclogs and Removes Hair, Soap Scum and Blockages, 80 OzDrano is one of those products that’s controversial among plumbers. Although it includes powerful chemicals that can dissolve even tough clogs, those chemicals are so powerful

that it can also, over time, melt pipes and break down the glue that holds PVC piping together. For these reasons, many plumbers advise against using Drano to clear a clog. It’s also

very toxic, which makes it a hazard to have in the home and not environmentally friendly.

That said, of the chemical options, Drano is far more effective than the home remedies mentioned above, largely because of its ability to melt clogs. Using Drano is easy. Simply open the bottle, dump the contents into the drain, wait about 20 minutes, and rinse with hot water.

Step 5. Snake the Drain

If all of the above have failed, don’t throw in the towel just yet. It’s simply time to bring out the big guns. Whereas the above solutions present mainly chemical means of removing a clog, the options below will physically engage the clog to work through it.

1. Drain snake

Drainsoon Auger 25 Ft with Gloves, Plumbing Snake Drain Auger Hair Clog Remover, Heavy Duty Pipe Drain Clog Remover for Bathtub Drain, Bathroom Sink, Kitchen and Shower Drain CleaningA manual drain snake consists of a long flexible metal cable with a coil on one end and a rotatable handle on the other. To use, thread the coiled auger end into the drain and push it through the P trap. Using the handled end, begin unwinding the metal auger into the hole. Rotate the auger at an even speed until you feel it hit the clog.

Once you feel the clog, rotate the head back and forth and move it around to attempt to break it up. Continue snaking until you don’t feel the obstruction. Should the tip become stuck, attempt to pull it free along with whatever is clogging the line.

2. Drain cleaning auger:

POPULO 20V Electric Drain Snake,25Ft Plumbing Snake Drain Clog Remover Tools with 2.0AH Battery and Charger,Snake Drain Hair Removal Tool for Toilet,Sewer, Bathroom,Sink and Shower 3/4'-2' PipeIf the drain snake doesn’t work, then you likely have a tougher clog on your hand. If you call a plumber, they’ll bring out a power auger to clear the drain. This consists of an electric motor that spins a metal snake, driving it through the line.

Although these augers are much more powerful than a standard drain snake, there are a few things to keep in mind before going this route. You’ll need to rent one of these machines, which can cost $50 or more per day. While this is far cheaper than hiring a plumber, it is more expensive than the other solutions on this list.

A power auger is also very heavy, weighing as much as 200 pounds, so you’ll need help if you plan on getting it into the basement. You’ll also need to take safety precautions. These machines spin a metal line using a powerful motor as you feed it into the drain with your hands.

Gloves are a must. You’ll need to be careful with the machine to prevent the line from wrapping around your wrists. To use this method, first use a plumber’s wrench to remove the cap on the cleanout in the drain.

Drain cleaning augers come with a variety of different heads for cutting through different types of clogs. These include a head for cutting through grease, a saw tip for cutting through roots, a retrieval tool for removing objects, and a standard drill bit.

If you’re not sure what the nature of the clog is, start with the standard bit.

Once you’ve attached the tip, begin pushing the head of the auger into the line. Once it’s a few feet in, start the motor. A foot pedal lets you engage or disengage the motor. This allows you to keep both hands on the line or cut the power quickly if you lose control.

Keep running the line until the drainpipe reaches the obstruction. Once you feel the cable hit, stop the machine and reverse it slightly to release the tension on the cable before driving it forward.

You’ll need to feed the cable slowly forward to allow it to chew through the clog without putting too much tension on the cable, which can cause the cable to wrap around your arm. When done, retract the cable and reattach the lid to the cleanout.

Step 6. Clean Up

Once the clog has been repaired and the crisis is over, get to work cleaning up. Sewage presents a bevy of health risks, some of which are serious. Exposure to sewage can cause dysentery, Hepatitis A, and salmonellosis. Even the gases created by sewage are enough to make one ill.

For this reason, it’s crucial to conduct a deep cleaning once the clog is fixed. Begin by removing any items that were damaged in the backflow. Soft items such as pillows and towels should be thrown away.

Clean the area thoroughly using soap and water and finish by coating the floor in a bleach solution as the bleach will kill any bacteria left from the sewage.

How to Prevent Basement Drain From Backing Up


1. Unclog and Clean Main Sewage Line

If you have a main sewer line that is susceptible to clogs, then it’s best to clean it about once a year as a preventative measure. Invest in a manual plumber snake and run it through the line following the method described above. Running the auger through the line will help break up any build-up that is beginning to form before it has the chance to create a clog and cause backflow.

Another preventative measure is to use enzyme cleaners to keep the drain clear by dumping it directly into the drain. Enzyme cleaners help prevent build-up in the lines and are much safer for the environment than chemical cleaners.

2. Unclog Basement Floor Drain

Unfinished basements typically have debris and dirt on the floor, much of which ends up in the drain. Keep the basement floor drain clean by periodically cleaning out the grate covering the drain and trap below. To clean the trap, open the grate and run a plumbing snake through the P trap. Enzyme cleaner will also keep the trap clean.

3. Install a Sewer Backflow Valve

The best way to prevent a basement drain from backing up is to install a reverse valve that prevents water from coming back through the drain. This simple device consists of a floating ball. When water is flowing through the drain, the ball stays out of the way.

Should a backflow occur, the ball floats into the drain hole, blocking the line and prevent sewage from passing through the drain and onto the basement floor. Keep in mind that a ball check valve can catch dirt and debris, making a drain easier to clog. If you install one, make sure to clean the drain regularly.

4. Cut trees and shrubs back.

While this may not always be possible, once you identify where the main sewer line travels through the yard, avoiding planting any trees or shrubs near the line to prevent roots from growing into it.

Does Homeowners Insurance Cover Sewer and Drain Backup?

Unfortunately, sewer backups are never covered under most homeowner’s insurance. However, many insurance companies offer sewer backup endorsements that can cover $10,000 worth of damage, which is enough for moderate damage but not extensive damage to the structure of the home.

This is significant, given that municipalities generally aren’t liable for any sewage backups caused by blockages in the sewer lines unless they are grossly negligent in maintaining the lines.

While city sewer backups that cause catastrophic damage to people’s homes are rare, they do happen, so it’s important to consider outfitting your home with a valve that prevents sewage backups from occurring.


While backed-up basement drains can be an unpleasant headache to deal with, a clogged main sewer line is a problem many homeowners can tackle on their own either with simple tools such as a plunger or manual plumbing snake and household products such as baking soda, vinegar, or even a bottle of soda.

As the old adage says, an ounce of prevention is worth a pound of cure. Periodically cleaning the main sewer line in your home with a manual plumbing snake or cleaning enzymes can help prevent backups.

Whatever strategy you choose, make sure to take the necessary safety precautions when dealing with a sewage backup to protect yourself from electrical shock and the dangerous pathogens and bacteria that exist in sewage.

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.

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