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Basement Drain Backing Up? Here’s How To Fix & Prevent It

A basement that is flooded with a floating couch, plant, and end table with a light on it.

When there is an issue with a sewer line, wastewater can flow back to the drain line. With a clogged line, the water will move to the lowest part of the house, which is always the basement. Fortunately, a sump pump can prevent a basement drain from backing up

Nothing is more unpleasant for homeowners than dealing with backed-up wastewater in the basement. In fact, a basement drain backing up can give a home a foul odor making it impossible for anyone to stay indoors.

On top of that, the high moisture level can promote mold and bacteria growth. It’s important to know how to do more than control the smell when fixing the basement drain backing up.

What You Need to Know About Drains Backing Up

If you’re experiencing basement drain backing-up problems, the culprit might be your drain line. Before proceeding to the sewer line, all of these drains pass through the home’s primary drain line:

  • bathtubs
  • sinks
  • toilets

When there is a clog in the drain line, the wastewater backs to the lowest exit point in the house, which is usually the basement.

The basement drain backing up can also happen due to rainwater or groundwater getting into the sewer system. Other causes of this problem include:

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  • tree roots
  • debris
  • grease

Here are some critical signs of a basement drain backing up. Not to worry, we’ll talk about how to fix these issues too!

#1: A Slow Draining Basement Drain

If the sink or tub stays filled up after use, it could be a slow-draining issue, commonly triggered by soap and hair buildup.

A toilet or sink issue can be caused by wads of toilet paper. In the kitchen, a blockage may be from fat and grease buildup.

Slow draining in a particular part of the house means the pipe connecting it to the primary system is blocked. When all the drains in your home become slow, the sewer line may be clogged.

NOTE: Detecting a slow drain can be challenging, especially since sewer water can back up and drain without you knowing.

#2: A Foul Odor From the Basement

One of the key telltale signs of the basement drain backing up is a foul odor from the basement. The presence of a foul odor means that the drain line is backing up, resulting in sewer water in the basement.

Basement drain backing up? Here's how to fix and prevent the problem - explained at
If you notice a foul odor in the basement, check the drain

Why is the Basement Drain Backing Up After Rain?

Dealing with a wet basement can be costly. Unexpected wastewater can provide an ideal environment for mold to thrive, and can damage:

  • floors
  • walls
  • furniture

If irreplaceable items are stored in the basement, we stand to lose a lot of precious commodities.

Unfortunately, a basement drain can backing-up quite seriously during the rainy season. All the used water in the house drains to the basement before exiting outdoors and connecting to the municipal sewer system.

When the sewer system gets overwhelmed, the wastewater can return to your home using the same drain line. Take a look at this 5-minute video for more detail on this type of issue:

Heavy rains can force the sewer system to handle rainwater and wastewater, clogging the lines. Even a reliable municipal sewer waste system that rarely fails can be overwhelmed by heavy rains.

Excess water forces the sewer waste to drain back into the home’s system. If the problem is with the sewer system, then your home may not be the only one affected. Confirm if your neighbors are also affected by the basement drain backing up.

Key Steps to Unclogging a Blocked Drain

Unclogging a blocked drain is easy; it’s not necessary to hire a plumber. Even if the drain line is clogged, do the following:

  1. Start by taking the necessary precautions.
  2. Get rid of the standing water.
  3. Clean the P-trap.
  4. Clean and unblock the drain using a plunger or chemicals.
  5. Finally, you can clean the basement.

With the right tools and patience, you can unclog your basement drain in no time and save some cash in the process!

What You Will Need When Fixing A Blocked Drain

When wastewater backs into your basement, it creates a hazardous environment filled with bacteria and pathogens. Use reliable protective gear, that includes the following (I’ve linked to the products on Amazon where available):

Other requirements:

To snake the drain, you’ll need the following:

  1. A huge bucket.
  2. Pieces of cloth for cleaning the splashing water.
  3. A drain snake. The drill can help you unclog the drain, but consider the length of its cable.
  4. A commercial drum auger may be needed for a heavy-duty blockage.
a clogged pipe with roots growing from the top.
More serious drain clogs require a drum auger

Steps to Fix Basement Drain Back Up

Now that you know the cause and symptoms of basement drain backing up, the next step is learning how to deal with waste water backing up in the basement. If you notice a foul odor from the basement, you should inspect the drain and confirm if the water is backing up when you use your sink.

Remember, slow draining can be quite challenging to notice so you may have to open some of the faucets in the house to confirm. If the kitchen sink is the problem, unclog it using hot water. When dealing with a flooded basement, you must be very creative.

To fix a basement drain that is backing up, follow these steps:

Step #1: Take the Necessary Precautions

If the basement is flooded, or there is standing water around the drain, start by taking the necessary safety precautions.

If there are power lines running through the basement the water is an electrical shock hazard. The first thing to do is switch off the electricity at the mains.

Backed-up water from the sewer system contains bacteria and pathogens, so wear protective gear before doing anything. Make sure to cover every body part before entering the basement.  

Step #2: Get Rid of the Standing Water

Examine the water level and confirm if it’s still rising. If so, shut off all the faucets in the house.

TIP: With everything off, you won’t be able to use water in your home until the issue is repaired.

Use a portable pump and a hose to pump the water out through the basement window. If there isn’t an exit window for the water, pump it into some buckets and pour them outside.

Another option is to try plunging to get the drain working again and remove the water.

Step #3: Clean the P-Trap

After removing the water, easily access the drain and clean its P-trap. Simply remove the grate cover and the backflow preventer to access the P-trap.

Next, try to clear the P-trap using a wet-dry vacuum. If the problem is at the P-trap, this will fix it.

If the drain is still clogged, locate its cleanout plug and remove it using a pipe wrench to access the home’s drain line.

Step #4: Clean the Drain With a Plunger and Chemicals

Once you access the drain line, there are several methods to try to remove the stubborn clogs. Some of the most popular and affordable methods include:

#1: A Plunger

A drain plunger is one of the most affordable and reliable methods to unclog your sewer line. It can create the needed suction to dislodge and push the clog through the pipe.

A plunger can be effective, especially when dealing with a minor clog. For it to work, an air-tight seal covering the drain must be created.

Pour some water around the drain to ensure that the plunger’s lip is underwater to create the seal. Next, push the plunger’s handle up and down until the clog is removed.

If this method doesn’t work, then it means that the problem is more serious and it’s time to try other techniques.

#2: Vinegar and Baking Soda

Another simple remedy for a clogged drain that has been used for decades is baking soda and vinegar. These ingredients are readily available and not hazardous; we use them in our homes every day. Here’s an example of it being used for this specific purpose:

HOT TIP: If you don’t have a plunger, this can be the first method to try.

For this method, use about 1.5 gallons of hot water, cold water won’t work.

Slowly pour the hot water into the drain pipe. Next, pour half a cup of baking soda down the drain. Finally, run a cup of vinegar into the drain. A mixture of vinegar and baking soda can create a volcano, so you must do it slowly. Seal the drain for a few minutes and let the mix clear the drain.

The fizzing reaction produced by a mixture of vinegar and baking soda can break the clogs apart. After a few minutes, clean the drain by pouring more hot water into it.

#3: Unclog the Drain Using Coca-Cola

This method may sound strange, especially since Coca-Cola is a popular beverage, but it can unclog a blocked drain. It’s loaded with phosphoric acid, which plays a crucial role in dislodging the buildup.

For this method, dump 2 liters of Coca-Cola into the drain and let it sit for two hours, then flush it with hot water. Coca-cola can come in handy when dealing with minor clogging, but if the problem persists, try snaking the drain.

#4: Snaking the Drain

If all the above methods don’t work, physically remove the clog through snaking.

Snaking means unclogging your sewage line using a drain snake which can pierce through the clog.

If the clog isn’t severe, start with a manual drain snake. Use the bigger one depending on how bad the clog is. Here’s a video for some more detail:

Drain Snake

The drain snake is a manual drain unclogging tool featuring a long cable with a rotating handle on one end and a coil on the other. Here’s an example of one on Amazon.

Insert the coil end into the drain and through the P-trap to use it. Unwind the auger into the drain at an even speed.

Continue to insert the snake into the drain until you hit the clog, then rotate the drain snake’s head until it pierces through the clog. Continue snaking until you remove the blockage.

Drain Cleaning Auger

If it’s a tough clog that a manual drain snake can’t dislodge, try a powerful option like this drain-cleaning auger sold on Amazon. This auger is more potent than a standard auger but is more costly.

Sometimes they can be rented, but if you have the budget, we recommend purchasing one. Weighing about 200 pounds, it may take two people to get it down to the basement.

Unlike the manual option, this unit has a powerful motor that spins the metal line. It still needs to be fed it into the drain manually. It comes with different heads to help unclog the drain.

One of the heads for this tool can even cut through roots. Besides a standard drill bit, it has a device for removing objects.

If you don’t know the extent of the clogging, start with a standard bit. Insert the bit head into the drain line, and after a few feet start the motor. Since it has a powerful motor, hold it with two hands.

Fortunately, it can dislodge over a 2-inch thick blockage, getting the job done. It also has a 25 ft. flexible cable that works with most drains and is ideal for L or S-shaped pipes.

A basement in progress of being finished with a stone wall and wood beams.
For safety, it is important to clean well after a drain backup

Step #5: Clean Up

After removing the clog, repair all the damage and clean the basement. Remember, sewage is a health hazard and can spread illnesses, including:

  • salmonellosis
  • Hepatitis A
  • dysentery

Therefore, clean the entire floor using water and soap before disinfecting it. Bleach will kill the bacteria left behind by the wastewater.

How to Prevent the Basement Drain From Backing Up

The best cure for any problem is prevention. Fortunately, you can do a few things to prevent this problem in the future. A simple thing such as regularly maintaining the drain line can do the trick.

Try these methods to prevent the drain from backing up in the future.

#1: Unclog the Sewage Line

If you have previously dealt with the basement drain backing up, the problem may be with the main sewage line. If you can access it, unclog it once per year. All you have to do is run a manual plumbing snake through it.

Unclogging the drain will stop the problem before it worsens. Pouring an enzyme cleaner like this one from Amazon, through the drain can also work perfectly.

#2: Unclog the Basement Drain Regularly

You will likely deal with a basement drain backing up if you have an unfinished basement because of the dirt and debris. Keeping the floor and grate covering clean can prevent this problem.

An enzyme cleaner can also help unclog the drain.

#3: Cut the Shrubs and Trees Near Your Drain Line

If it’s a new house, you should find where the sewage line passes and cut all the trees growing there. Also, avoid planting trees near the drain line since the roots can damage the drain, causing the basement drain to back up during the rainy season.

A grassy area with a sewage line access, with the top grate off the hole and set to the side.
The main sewage line may be the issue


Dealing with a basement drain backing up can be devastating, especially if the basement is smelly and flooded. But with the above few practical and easy steps, your drain will be unclogged in no time.

So before you call a plumber, try these steps. It may be a minor issue that you can clear yourself.

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