Drain Backup in the Basement: How to Fix?

Is your drain backing up in your basement? You don’t need to panic even though you need to fix it as soon as possible.

Here’s how to fix your drain backup in the Basement. But first, let’s discuss the common causes of drain backup in the basement.

drain backup in basement

Causes of Drain Backup in Basement

The following are common causes of basement drain backups:

Clogs in the Drain Pipe(s)

Wastewater from the toilet(s), sink(s), and bathtub(s)/shower(s) drains into the drain pipes and subsequently into the main drain line. If your main drain pipe or any of the drain pipes is clogged, sewage or wastewater from these drains will flow back through the lowest exit into your basement.

For instance, if a toilet or shower backs up into your basement, the drain connected to that toilet or shower is likely clogged. However, if all your toilets, showers, or sinks back up into your basement, the main drain line may be clogged.

When there is a backup when you flush your toilet, drain the kitchen sink, use the shower, use the washing machine, or when it rains, this is an indication that the main drain line is clogged.

Anything can constitute the clogs in your drain pipe, such as hair, thick toilet paper, paper towels, flushable wipes, toys, feminine products, and/or other solid materials.

Clogs in the Vent Stack

The vent stack is a pipe that sticks out of your roof and is an important part of your home’s plumbing system.

The vent stack provides an opening that allows the entry and exit of air. This regulates the air pressure in your plumbing system, enabling wastewater to flow smoothly and awful odors to escape.

Sometimes, the vent stack can become clogged, resulting in reduced air pressure in the plumbing system. This can result in slow drainage, toilet bubbles, and drain backup, especially if the drain line is located in the basement.

Tree Roots

Tree roots can also cause drain backup in your basement when they clog the main sewer pipe.

Naturally, tree roots like moisture and can crawl anywhere they can find moisture. One such place where tree roots can find moisture is the sewer pipe, especially if the pipe is cracked.

Once tree roots get to the sewer pipe, they may penetrate it and continue to grow until it clogs the pipe.

The tree roots may also grow around the pipe and crush it. Any of these actions can cause drain backup in your basement.

Damaged Drain/Sewer Pipes

The type of pipe you use for your drain matters a lot. Your drain/sewer pipes tend to deteriorate due to old age and harsh weather or environmental conditions, and deteriorated pipes can crack or break. This can lead to drain backup in your basement.

Heavy Rainfall, Flooding, or Storms

This is common with those whose sewer drain is connected to the public or city sewer system.

Large amounts of rainfall or flood can inundate the public sewer system with water. Once the public sewer system is overloaded and can no longer handle excess water, the water will find its way into connected drain/sewer pipes. This backflow of water can cause drain backup in your basement.

Draining Too Much Water

Sometimes, the drain backup happens when the main drain pipe has to handle too much wastewater. Most main drain lines have a diameter of four inches and should be able to efficiently drain wastewater at 160 gallons per minute.

However, sediment or mineral buildups, clogs, or any foreign body can lower this efficiency.

This will, in turn, cause backflow into the basement when too much wastewater is drained.

Poor Angle of Slope

The poor angle of slope is often another reason why most drain backups in the basement occur. The main drain pipe must be installed at the correct slope for the effective flow of wastewater.

When the drain pipe slants downwards, the slope will aid gravity to transport the wastewater from the toilet fixtures. However, if the main drain pipe is poorly sloped or not slopped at all, drain backup in your basement may occur.

Belly in The Main Drain Line

Finally, a belly in the main drain line is another reason why drain backup in the basement can occur.

A belly is a dip or downward bent section in the main drain line. A belly forms over time along the main drain pipe as the ground shifts or settles. Other causes of a belly in the main drain line include temperature changes, tree roots, and so on.

The belly, usually a U-shape downward sag, will affect the flow of wastewater in the main sewer pipe, especially if too much wastewater is running in the pipe. This can cause the drain to back up into the basement.

All of the above are the possible causes of drain backup in the basement. However, the best way to identify the exact cause of drain backup in your basement is to contact a professional and experienced plumber.

cleaning backup up dirty water

How to Fix Drain Backup in Basement

While some causes of drain backup in your issues can be easily fixed with simple tools, others require professional expertise and more specialized tools.

Sometimes, a simple cleaning or declogging will solve the issue but more serious causes need a proper inspection, diagnosis, and repair.

Here’s what to do if the drain backs up in your basement:

Step 1: Take Necessary Safety Precautions

You’re dealing with wastewater or sewage that may contain pathogens, germs, and bacteria. So, it’s best practice to put on a pair of latex gloves to protect your hands.

Put on a nose mask as you’ll be exposed to awful odors and foul smells from the wastewater. Also, put on a pair of safety goggles to protect your eyes from splashes.

Finally, turn off the electricity supply to the basement to avoid the risk of electrical shock, especially if you have electrical wires running through your basement.

Step 2: Get Rid of Standing Wastewater in the Basement

The next step is to remove any standing wastewater on the basement floor. It’s possible that you have some wastewater lying on the floor, especially in a severe case of drain backup. Remove this wastewater so that it doesn’t cause more damage or hazards.

Depending on what is available to you, you can use a foam, sponge, towel, or portable wet vacuum pump to remove the standing wastewater in the basement. If this seems difficult, try to plunge the drain to see if it works again at getting the wastewater out. Otherwise, you would have to patiently get rid of the wastewater using any of the former methods.

Step 3: Clean the P-trap

Once the standing wastewater is out and you can access the drain, clean out the drain’s P-trap. You will have to remove the drain/grate cover (and backflow preventer) to access the P-trap.

Use a short drain snake or wet vacuum to clear out the P-trap. If this doesn’t solve the problem, locate and remove the cleanout plug using a wrench. This will enable you to access the main drain pipe.

Step 4: Remove the Clogs in the Main Drain Line

Now that you have accessed the main drain line, you can remove the clogs using a plunger, drain snake, or chemicals.

A plunger will help you to dislodge the clog by creating a suction that pushes the clog through the drain pipe. Place the plunger around the drain to create an air-tight seal (add water if necessary). Plunge the drain thoroughly until the clog is removed. Please note that a plunger is only effective for minor clogs.

If a plunger doesn’t work, try using chemicals. A solution of baking soda and vinegar is a well-known home remedy for removing clogs.

Pour a half cup of baking soda into the drain pipe. Also, add a cup of vinegar to the drain pipe and seal the pipe for about 10 minutes. The mixture should fizzle out and break the clogs apart.

After that, pour some hot water into the main drain pipe to complete the cleaning. In place of baking soda and vinegar, you can also use Coca-Cola. Does that sound surprising?

Coca-Cola contains phosphoric acid, which is effective at breaking down clogs and buildups in the drain pipe. Pour about 2 liters of Coca-Cola into the clogged drain and leave it for about an hour to work on the clog. After that, flush the drain with boiling water.

There are chemical products specially made to de-clog your toilet. These products contain powerful chemicals that can dissolve clogs. However, you need to be careful when choosing any of these products as most of them are harsh on drain pipes and are not environmentally friendly.

If none of the steps above worked, try using a heavy-duty drain snake to de-clog your man drain line. You can use either a manual drain snake or a power drain snake.

If you’re using a manual drain snake, insert the snake head into the drain and begin rotating the handle clockwise to push the drain snake into the drain. Rotate the drain snake until the snake hits the clog. Keep rotating the snake forth and back to break into the clog.

If you no longer feel any obstruction, the clog is broken up. If you feel that the snake head is stuck into something, rotate the drain snake anticlockwise to pull out whatever is clogging the drain pipe.

A power drain snake works in a similar way as a manual drain snake just that it uses a powerful motor and spins faster.

Step 5: Clean Up the Basement

After removing the wastewater and cleaning the P-trap and drain line, you need to clean the basement thoroughly with soap and water. You can also coat the basement floor with a bleach solution or any other disinfectant to kill any bacteria from the sewage.

Discard any item that you can’t salvage, such as fabric, wood furniture, carpet, and so on. These items would have been soaked up with the wastewater. Also, open any vents or windows in the basement to allow the escape of foul smell.

Following the steps above will enable you to fix the drain backup in your basement. However, if you’re dealing with a drain backup emergency, calling on a professional plumber is the best move.

How to Prevent a Drain Backup in Your Basement

Preventing a drain backup in your basement is better than fixing a drain backup. Here are effective ways to prevent a drain backup in your basement:

Don’t Flush Foreign Bodies in Your Toilet

The only thing that should go down the drain or toilet is wastewater. Flushing foreign bodies like hair, grease, pad, flushable wipes, and so on, can clog the toilet and cause drain backup.

If you’re so careful to avoid flushing foreign bodies down your drain or toilet, you can prevent a drain backup in your basement.

Remove Tree Roots from Around your Drain Pipe

Tree roots can either wind around the drain pipe and damage it or penetrate the pipe and break it. The best thing to do is to cut the tree around the drain pipe and/or remove its roots. Otherwise, the tree roots may cause a drain backup problem.

Remove the Clog in the Vent Stack

Accumulation of dirt or debris in the vent stack can clog the vent stack and this can subsequently lead to a drain backup.

Using any suitable equipment, climb on your rooftop and check inside the vent pipe for any visible clogs like a bird nest, leaves, and so on. Remove any clog in the vent stack to prevent the occurrence of drain backup.

flooded basement

Install a New Drain Pipe

As mentioned earlier, a damaged drain pipe or a drain pipe with a belly can cause drain backup. If you realize that your drain pipe has been damaged by tree roots or any other factor, call on a professional to replace it with a new one.

Old drain lines are also prone to damage. Replace your old drain line as soon as possible. Doing this will save you more money in the end. Also, call on a professional to run a check on your drain pipe for bellies or poor angle of slope.

Install a Drain Backflow Prevention Valve

Another way to prevent a drain backup in your basement is to install a drain backflow prevention valve. This valve allows wastewater or sewage to leave the drain but blocks it from coming back through the drain, preventing drain backup in your basement.

While a drain backflow prevention valve is effective at preventing drain backflow, it also catches dirt and debris, which can easily clog the drain pipe. So, if you install a drain backflow prevention valve, make sure that you clean your drain pipe regularly.


Having a drain backup in your basement can be quite an experience. Fixing it on your own can also be difficult and time-consuming. The best thing to do is to call on a professional plumber, who will easily fix the problem for you.

To prevent a drain backup in your basement, avoid flushing foreign bodies down the toilet/drain, clear the vent stack regularly, install a new drain pipe if it’s damaged or old, and install a drain backflow prevention valve. Doing all these will enable you to prevent a drain backup in your basement.

Also, don’t forget to check with your local municipality or city hall for any regulations regarding this. Doing so will ensure that you comply with all local regulations.

Following these steps will help ensure that you stay safe and prevent a drain backup in your basement. Good luck!

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