Basement Drain Backing Up When Washing Clothes? (Here's Why)

Nick Durante
by Nick Durante
Standing water in your basement often traces back to the floor drain, and it is never a good sign when it backs up while you’re doing laundry. This can be caused by several key problems ranging from a clogged line to a blockage in the pipe. Luckily, most of these problems have simple fixes, so follow along as we explore what you should do when your basement drain backs up when you wash clothes.

When you are washing your clothes, the last thing you’re expecting is the basement drain to back up. That is unless your basement drain continually backs up often when you do the laundry. This problem is more common than you might think. Luckily, there are a few things you can do that will stop your basement drain from backing up when washing clothes.

If your basement drain is backing up when washing clothes, the most likely cause is a blocked drainpipe. Watch the basement drain as you run the washing machine. If it overflows as the water is released, something is clogging either the line or the plumbing vent pipe. However, if there is no clear blockage, this could mean that you need to install a larger drain pipe.

It is bad news when your basement drain backs up, especially if there is carpet nearby. Let’s get to the root of the problem and fix your basement drain so that you can wash clothes without worry.

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Possible Causes

Several things can cause a basement drain to back up when washing clothes. Generally, a handy homeowner can easily remedy the problem, depending on the severity and the cause, and unclog the basement drain. Blockages are the most common cause for your basement drain backing up, and it is the easiest problem to solve.

The two main areas that can get clogged and lead to a backup are the drainpipe and vent pipe. If you cannot identify any blockage in either area, it could mean that your drainpipe is too small and needs to be replaced.


A blockage in the pipes between your washing machine and the basement drain can cause it to back up. When you wash your clothes, small fibers from your clothes can build up over time in the drain system. Also, just think of those tissues, change, and other small items that accidentally made their way from the dirty clothes pile to your machine.

If your drains are clogged for any of these reasons, you can get rid of these blockages by using a hose, drain bladder, Drano, a snake, or an auger.

How to Fix a Blockage

Step 1: Inspect the drain

Inspect the drain with a flashlight to look for clear blockages and remove them using a wet/dry shop vac, or an auger.

Step 2: Remove the clean-out plug cap

If blockages are unclear, remove the cap for the clean-out plug located near the basement drain.

Step 3: Clean pipe using a snake or auger

Push a snake or an auger through the clean-out plug and work it down the pipe until you reach the blockage. Remove the blockage by pulling on it with the snake or auger until it is all out of the drain.

Step 4: Add water to the P-trap

Re-attach the cap to the clean-out plug and dump water into the P-trap so that sewer odors can’t escape.

You can rent an auger for $100-$120 at places like Home Depot, and a snake for $50-$100. Otherwise, a wet/dry shop vac is great for mild blockages.

Basement Drain Backing Up: Here Is How To Fix It

High Water Pressure

In some cases, basement drains back up or overflow when the washer runs because too much water is exiting through the pipe at once.

Depending on the washing machine, it may use 30-40 gallons of water while running, which creates an enormous amount of pressure. A clogged pipe creates even more pressure as that water has trouble passing through. This increase in pressure and resistance can easily cause the basement floor drain to back up when washing clothes.

Old plumbing sometimes is not able to handle the rush of water from running a washing machine. When the pipes get overwhelmed by the large volume of water, it causes the basement floor drain to back up or overflow.

Basement drains that have even the slightest blockage are more susceptible to a high volume of water overloading them. If you carefully snake the pipe, you can usually remove the blockage easily and on your own.

How to Regulate the Water Pressure

Unfortunately, if your pipes are the problem, you may need to hire a plumber to make the fix. Inspect your pipes and measure their diameter. If your pipes measure 1 ¼”-1 ½” that is typically too small to handle the amount of water exiting a washing machine.

This means that you will likely need to get new pipes that can handle the water flow. Choose a drain line that is 2” in diameter, as it should handle the water from a running washer. Replacing drainpipes can cost between $200 and $1,000, but if your drainpipe is too small, it is necessary. Otherwise, you could experience water damage from your drain overflow. This means that you will also be tacking on these extra repairs to the bill.

Clogged Plumbing Vent Pipe

While it may be far from your basement drain, a clogged plumbing vent pipe can cause it to back up. Your plumbing vent pipe is located on your roof, and it is integral to your home’s plumbing system. This vent allows air to flow through your pipes so your drains work properly. If this vent becomes clogged, it causes a vacuum and your pipes will drain very slowly.

Dust, leaves, debris, and even birds’ nests are common culprits for a blocked vent pipe. Because it is on the roof, you should get the help of a friend before attempting to remove the blockage.

How to Fix a Clogged Plumbing Vent Pipe

Step 1: Remove visible debris

Remove the top cap from the plumbing vent pipe on your roof. Pull any visible debris out of the vent pipe by hand if it is near the top and look down the pipe with a flashlight to look for more.

Step 2: Use a snake or auger to break up blockage

Lower a snake or auger into the vent pipe until it reaches the blockage. Push the snake or auger as hard as you need to in order to break up the blockage. Once you feel no more resistance, remove the snake/auger.

Step 3: Clean vent pipe with water

Pour or spray water down the vent pipe, then look back inside of it with the flashlight. If there is no more blockage, put the cap back on the vent pipe, and carefully climb off of the roof.

Damaged Drain Hose

If your drain hose was damaged or has a knot or a kink in it, this can cause backflow to your washing machine. You want to make sure that your drain hose runs as straight as possible from your washing machine to the connecting standpipe without too many twists and turns. Also, be especially careful that you don’t squash your drain hose when you adjust the position of your washer.

How to Prevent Backflow to Your Washing Machine

No one wants dirty water re-entering the wash. To make sure that your dirty water drains and doesn’t flow back to your washer, you can install a few simple devices.

Backwater valve

A backwater valve keeps water and sewage from flowing in the wrong direction and dirtying your clean water sources. If your drain is in the basement (below an upstream manhole), a backwater valve is generally required.

Backflow plugs

A backflow plug is a rubber floating device that you install in your drain. If water starts to flow in the wrong direction, it will push this plug and effectively close off the pipe. This will prevent backflow from entering clean water sources. Here are a few different types of backflow plugs you may come across:

  • Ball plugs 
  • Pressure plugs 
  • Twist plugs 
  • Threaded caps 

These devices may not prevent blockage, but they will protect your clean water from contamination if your drain is not working properly.

What If There Is a Sewer Smell When Basement Drain Backs Up?

If there is a sewer smell when your basement drain backs up, it could mean that the standpipe is dry. The standpipe is an elbow-shaped pipe that works like a P-trap for washing machines. When the drain and adjacent trap dry out, sewer odors can come out. Traps keep sewer gases and odor from seeping out because there is constantly water there as a barrier.

However, if the standpipe was recently dried out, sewer odors will come up and out of the basement floor drain. Sometimes, the water from the washing machine may be enough to replace the water in the trap. If not, all that you need to do is pour water into the drain, and the trap will be filled.

Most of the time, the water backing up from the washing machine will at the very least eliminate the sewer odor. The overflow will fill the trap, although you’ll need to use one of the above remedies to remove the clog and backup.

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What Did We Learn?

When your basement drain backs up when washing clothes, it is usually due to a blockage in the drainpipe. You can easily remove debris in the basement drain using a shop vac or using a snake or auger. Before using any plumbing tools, always inspect the drain with a flashlight in case the blockage is at the top.

If your drainpipe is fine, carefully inspect your plumbing vent pipe on the roof. Remove any blockages using an auger or a snake just like with a drainpipe. However, in some cases, the blockage is not the cause of your basement drain backing up when washing clothes.

Replacing drainpipes may be necessary if you cannot find any blockages in the line or in the plumbing vent. Contact a plumber if there is nothing apparent causing a blockage or if your drainpipe is only 1 ½” in diameter.

Regular check-ups from a plumber can prevent serious issues and will keep your basement drain in top shape.

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Nick Durante
Nick Durante

Nick Durante is a professional writer with a primary focus on home improvement. When he is not writing about home improvement or taking on projects around the house, he likes to read and create art. He is always looking towards the newest trends in home improvement.

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