My washing machine drain smells like sewage — What Do I Do?

AllClear 8:59 pm

My washing machine drain smells like sewage — What Do I Do?

Have you noticed a sulfur-like, rotten eggs type of smell coming from your laundry room recently? If your washing machine drain smells like sewage it can be incredibly unpleasant. This stench makes a room usually known for cleaning turn into a zone in your home that you avoid at all costs. Breathing in sewer gases over a long period can be detrimental to your health, and if you can’t diagnose and correct the problem quickly on your own, you need to call a plumber to sort out the issue.  

This problem is more common than you would think – everyone’s washing machine drain smells like sewage every once in a while. Luckily, the solutions are relatively simple. We’ve seen this issue hundreds of times over the years and fixing it can be straightforward. In some cases, you can even fix it yourself if you feel like rolling up your sleeves. In this post, we’ll go over the most common causes of a washing machine drain smelling like sewage and some DIY solutions you can try to fix the problem before calling the professionals.

washing machine stinks when run

Why Does My Washing Machine Drain Smell Like Sewage?

So why does this happen so frequently? To understand the causes, here’s a brief overview of how a washing machine is set up.

Modern washing machines typically come with a flexible plastic drain hose that can be easily inserted into standard washing machine drain boxes. Inside the washing machine drain box, you’ll find a p-trap which is usually inside the wall although it may be exposed in older homes.

washing machine drain smells like sewage

Through this setup, the wastewater from the washing machine flows through the plastic washing machine hose into the drain box pipe. The p-trap is then filled with the water to create a seal that prevents sewer gases from entering the house through the pipe.

More commonly than not, if the washing machine wasn’t installed correctly, the drain hose might have been inserted too far into the drainage box. If inserted too far, the hose will go past the p-trap which will defeat the purpose of the trap itself. If the hose is past the bend in the p-trap then there is no room for the water to collect and form the buffer between your clean laundry room and the foul-smelling sewer gases.  

Possible Remedies When Your Washing Machine Drain Smells Like Sewage

Because this is such a common problem, many quick fixes will take care of the nasty sewer smell lingering in your laundry room. Some fixes are faster than others, and they aren’t all guaranteed to fix your specific issue. That being said, each is worth a try and have been known to work in most minor cases.

washing machine odor

Clean Your Washing Machine

You can try running a load of hot water without clothes through the washing machine. We recommend adding a cup of distilled white vinegar as well to help clean out the drain pipe. If that doesn’t work and you suspect it could be a hard water issue, repeat the process but add some baking soda to help suspend hard water deposits.

Once the washing cycle completes, allow the space to dry by leaving the washing machine door open. This process will remove dirt, caked-on detergent, and water residue that causes a musty smell which is sometimes confused with sewage.

Replenish Your Drain Traps

If your home is fitted with floor drains (usually a circular grate close to the washing machine) in the laundry room or basement, pour a few gallons of water down it. This will help restore the water in the drain traps that protect your home from sewer gases. After the water, pour four ounces of mineral oil down the drain as well which will help slow down the evaporation of the water in the drain trap.

washing machine drain smells like sewage

Clear Any Drain Pipe Clogs

Your washing machine’s drain pipe might have a partial clog that you might not have noticed before. A clog in the drain line will often produce an offensive odor that can resemble sewer gas because the bacteria can form on the organic matter like hair or soap will often produce a nasty smell. If you have one, you can use a drain snake to help clear out any clogs in the drain pipe.

Check for Clogs in Your Vent Pipes

Every house’s drain system must be properly vented otherwise sewer gases can make their way into the home. The vent pipes are used to connect the central drain pipes through the home which gives a path for sewer gases to escape to the open air above the house’s roof. The vent pipes also allow fresh air to enter into the drain pipes which replaces any that washed down the pipes into the sewer.

To diagnose the issue, you’ll need to climb up to the roof. Once you’re on the roof, shine a flashlight down the vent pipes and check to see if there are any clogs. If you see any, take steps to remove them using a snake or other long tool safely. If you don’t feel comfortable doing this yourself, a plumber will have no issue analyzing your vent pipe set up to ensure it is working correctly and not causing any problems.

washing machine drain smells like sewage

If These Solutions Don’t Work

Not every quick fix will solve plumbing problems. If after cleaning the drain pipe and washing it out still doesn’t take care of the sewer smell, it can be safe to assume that the problem is more significant than a simple dry trap. Other potential causes of a sewer smell emanating from your washing machine drain could be leads, cracked drain pipes, significant clogs, or a stopped-up vent pipe. These issues are much more difficult to identify and fix if you don’t have the proper plumbing experience.  

Give the Friendly Plumbing Experts a Call

If these remedies don’t fix the problem, give All Clear Plumbing a call, and we’ll be happy to help you troubleshoot over the phone or come out and help with your plumbing repairs.

Article Author: Anja Smith

Managing Partner

Anja Smith is the author behind the All Clear Plumbing blog. She also writes regularly for Plumber Magazine,, and on Medium