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Why Washing Machine Drain Smells Like Rotten Eggs or Sewage
AAZparts Team
Updated on June 23, 2025
8 min read
A smelly washer drain is a common but frustrating issue that can leave your laundry room with an unpleasant odor, even after a wash cycle. The cause may be hidden residue, mold, or poor drainage all of which can affect your washing machine’s performance. In this guide, AZParts explains the causes of a smelly washer drain and provides effective solutions to eliminate the odor and prevent it from returning.
_11zon_1750647286.jpeg&w=3840&q=75 "smelly washer drain")
1. Why Does Washing Machine Smell?
A washing machine that smells unpleasant like mildew, must, or even wet dog is a common issue in many households. These odors are typically caused by moisture retention, detergent residue, mold growth, or poor maintenance habits. If not addressed, the smell can transfer onto your clothes and affect overall hygiene.
1.1. Detergent Buildup
Ironically, the very thing meant to clean your clothes might be dirtying your machine.
Most people use too much detergent or the wrong type, especially in high-efficiency (HE) washers. When excess detergent doesn’t rinse away, it leaves behind a sticky residue that traps dirt, grime, and bacteria, creating the perfect breeding ground for unpleasant smells.
What to do:
- Use HE-compatible, fragrance-free detergent.
- Run a hot wash with vinegar or a washing machine cleaner once a month.
1.2. Trapped Moisture
Washing machines, especially front-loaders, are sealed tight when closed. That’s great during a cycle, but if you leave the door shut afterward, leftover moisture inside the drum can’t escape.
This damp environment encourages mold and mildew growth, leading to that classic musty smell.
Quick fix: Leave the door slightly ajar after each wash to let the drum dry out completely.
1.3. A Dirty Rubber Gasket (Front-Loaders)
Dirty rubber gasket in washer (Source: Freepik)
If you own a front-loading washer, take a look at the rubber seal around the door. This washer gasket often traps water, hair, detergent residue, and even small clothing items like socks.
Over time, the buildup can turn slimy and start to stink.
What to do: Wipe down the gasket regularly using a cloth and a mild vinegar solution.
1.4. Clogged or Dirty Filter
Your washer’s filter catches lint, hair, and debris. But if it’s not cleaned regularly, it can become a source of odor and even affect how well your machine cleans your clothes.
Solution:
- Locate the filter (usually at the bottom front of the machine).
- Clean it out every few months, or more often if you wash pet bedding or heavily soiled clothes.
1.5. Poor Drainage
A smell like sewage could mean your washer isn’t draining properly. Clogged drain hoses, pipes, or filters can cause water to stagnate inside the machine.
Tip: Check for blockages in the hose and clean them as needed. If the smell persists, it might be time to call a professional.
1.6. Overloading the Washer
Smelly washer drain can caused by overloading (Source: Freepik)
Cramming your washer to the brim might save time but it can lead to poorly rinsed clothes and detergent buildup, which contributes to odor.
Best practice: Stick to the manufacturer’s recommended load size for optimal performance and freshness.
1.7. Inadequate Ventilation in the Laundry Room
If your laundry area is poorly ventilated, it can trap humidity, contributing to mold and mildew not just in your washer but also in the surrounding space.
Tip: Keep windows open when possible, use a dehumidifier, or install a small fan to keep air circulating.
2. Rotten Eggs Smell from a Washing Machine
Foul Odor Like Rotten Eggs Coming from the Washing Machine (Source: Freepik )
If your washing machine smells like rotten eggs, the issue is often due to bacterial buildup or, less commonly, a natural gas leak. Identifying the cause early helps prevent damage and unpleasant odors from spreading to your laundry.
2.1. Bacterial and Mold Growth
The most frequent cause of a rotten egg smell is the buildup of mold, mildew, soap scum, and lint inside the machine especially in front-loading washers. Moisture trapped around the rubber door gasket creates an ideal environment for bacteria to grow, often worsened by trapped items like socks or clothes behind the seal.
How to Fix It:
- Inspect and clean the rubber gasket:
- Pull back the seal to remove any debris or trapped items.
- Use a 1:1 solution of white vinegar and water (or bleach) to clean mold and buildup.
- Run a cleaning cycle:
- For front-load washers: Add 1/3 cup baking soda to the drum and 1 cup distilled white vinegar to the detergent tray.
- For top-load washers: Add 1/2 cup baking soda and 2 cups vinegar when the drum is half full of water.
Use the hottest, longest cycle available.
2.2. Natural Gas Leak (Less Common Reason)
Although rare, a persistent rotten egg smell near the washer may indicate a natural gas leak, as gas companies add sulfur to make leaks detectable.
How to fix it:
- If you suspect a gas leak, leave the area immediately and contact your gas provider.
Prevention Tips
- Keep the washer door open after each use to allow air circulation.
- Wipe down the drum and rubber seal regularly.
- Perform a deep clean monthly or as recommended by the manufacturer.
A rotten egg smell from your washing machine is usually a sign of poor maintenance or trapped moisture. Regular cleaning and ventilation are essential to prevent odors and maintain your washer’s performance. If the smell persists despite cleaning, always rule out more serious issues like a gas leak.
3. Sewage Smell from a Washing Machine
Smell from a Washing Machine (Source: AZParts)
One of the most overlooked causes of sewage odors is a dry or improperly installed P-trap. The P-trap is a plumbing fixture designed to hold water, creating a seal that blocks sewer gases from entering your home through the drain.
When the P-trap dries out often due to infrequent use or improper installation—it can no longer perform its role. As a result, sewer gas escapes through the standpipe and makes its way into your laundry room.
Solution: Pour approximately one gallon of water down the drainpipe. This helps re-establish the water seal inside the P-trap. If the smell persists, it’s recommended to contact a licensed plumber to inspect the drainage setup and ensure proper installation.
While addressing the P-trap is essential, a more proactive and long-term solution is to install a Pump Filter such as the high-performance filter available from AZParts. This pump filter is designed to capture debris, lint, hair, and other residues that typically build up in your drain system. Over time, these substances can rot and contribute to the foul sewage smell, especially in high-humidity environments like laundry areas.
Replacing new pump filter to prevent smell from a Washing Machine (Source: AZParts)
By trapping contaminants before they reach the drain,the Pump filter reduces the organic matter that causes odors and prevents buildup in the plumbing system.
4. Dried Out or Improperly Installed P-trap
A P-trap is an essential part of every drain in your home, including the one for your washing machine. It helps trap debris to prevent deep clogs and also holds a small amount of water to block sewer gases from escaping into your home.
If the P-trap has dried out or if the drain hose or trap was installed incorrectly, it won't be able to hold that water barrier. As a result, sewer odors can leak through the drain and make your laundry room smell unpleasant.
To fix this, pour about a gallon of water down the drain to refill the trap. If the smell persists, it’s best to call a professional plumber to check the installation and make sure everything is properly sealed and functioning.
5. How to Clean Clogged Washer Drain Pipe
Unclog a Washing Machine Drain Pipe (Source: AZParts)
Over time, buildup from detergent residue, lint, and dirt can restrict the flow in your washer’s drain hose or pipe. This slow buildup doesn’t just affect drainage, it also becomes a breeding ground for bacteria that produce strong sewer-like odors. If left unchecked, the blockage worsens, leading to more severe smells and even possible water backup.
How to Fix It: Professional plumbers use a tool called a sewer auger (or drain snake) to remove stubborn clogs from washer drain lines. This tool can be dangerous in untrained hands, so it’s best to avoid DIY attempts and contact a licensed plumber for a safe and effective solution.
6. How to Clear a Clogged Vent Pipe
Your washing machine is connected to a venting system that plays a key role in allowing water to flow freely and letting sewer gases escape outside, typically through your roof. If that vertical vent pipe becomes clogged by debris like leaves, twigs, or even animal nests, sewer gases may have no exit and will instead leak back into your laundry room.
What You Can Do: If you’re comfortable and it’s safe, access the roof and look down the vent pipe using a flashlight. Remove any visible obstructions by hand if reachable. For blockages deeper in the pipe or if roof access is risky, call in a plumbing expert who has the proper tools and training.
A persistent sewer smell from your washer drain often points to deeper plumbing issues like clogged pipes, blocked vents, or a dried-out P-trap. These problems can worsen over time, causing backups and foul odors throughout your laundry space. The key is early detection and proper maintenance.
Whether you're tackling the issue yourself or need expert assistance, AZParts offers the right washer parts and advice to help you restore a clean, odor-free laundry area. Trust AZParts as your go-to resource for reliable washer parts and practical solutions that keep your plumbing system running smoothly.
Contact Information:
8 The Green, Ste A, Dover, Delaware 19901-3618, United States
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