Why Does My Washing Machine Drain Smell Bad? Causes, Fixes, and How to Stop It Coming Back

If your laundry smells worse after a wash than before, your washing machine drain could be the source of the problem. Unpleasant odours from a washing machine or utility area are more common than most people realise. In many cases, a persistent drain smell is a warning sign of something building up inside the system—whether it's a blocked filter, trapped residue, or a problem deeper within the drainage pipework.

The good news is that many of these issues can be resolved with simple DIY maintenance. However, if ignored, they can evolve into more serious drainage problems, leading to overflows, backups, or damage that requires professional attention.

This article will cover:

• Common causes of washing machine drain odours

• Step-by-step instructions for eliminating the smell

• Signs that suggest a bigger drainage issue

• Preventative maintenance tips to keep your machine and drains smelling fresh

Common Causes of Washing Machine Drain Smells

Smelly drains are typically caused by a combination of residue build-up, stagnant water, and bacteria. Over time, detergent, fabric softener, skin cells, hair, and dirt accumulate in hidden parts of your machine and drainage system, creating the perfect environment for bacteria and mould to grow.

1. Detergent and Fabric Softener Residue

Using too much detergent or fabric softener, especially in low-temperature washes, can leave behind a soapy film that coats the inside of your drum, pipes, and drainage hose. This residue traps bacteria, which produces unpleasant smells over time.

2. Dirty or Partially Blocked Drain Hose

The drain hose carries used water away from the machine, but it can accumulate debris and biofilm on the inside walls. If the hose becomes blocked or partially restricted, water doesn’t drain properly, leading to stagnation and bad odours.

3. Standing Water in the Trap or Pipe

If your drain hose is not installed with the correct fall (angle), or the waste pipe is partially blocked, water can remain sitting in the pipe. Over time, this stagnant water begins to smell foul as bacteria thrive in the moist environment.

4. Mould and Mildew Inside the Machine

Moisture left behind after each cycle creates a breeding ground for mould, particularly in the rubber door seal and detergent drawer. If the door and drawer are kept closed after use, mould builds up more quickly.

5. Issues with the External Drainage System

Sometimes the smell isn’t coming from the machine at all. It could be due to issues in the connected waste pipes or external drainage system, such as a blocked gully, cracked drain, or rodent ingress.

How to Eliminate Washing Machine Drain Smells: Step-by-Step

Once you understand the potential sources of the smell, it’s time to take action. The following steps will help you clean your machine thoroughly and address any internal drainage issues that may be causing the odour.

Step 1: Clean the Filter

The filter, usually located at the bottom front of the machine behind a small flap, traps lint, coins, and other debris.

• Place a shallow tray or towel under the filter area to catch water.

• Unscrew or release the filter carefully.

• Remove all visible debris and rinse thoroughly with hot water.

• Use a toothbrush or soft cloth to clean the inside of the filter housing.

Step 2: Run a Hot Maintenance Cycle

Most odour-causing bacteria thrive in cold temperatures. A monthly maintenance wash at high temperature (90°C or higher) helps kill bacteria and dissolve soap residue.

• Run the machine empty on the hottest setting.

• Add 250 ml of white vinegar or a scoop of bicarbonate of soda to the drum (not both at once).

• Do not use detergent during this cycle.

Step 3: Clean the Detergent Drawer

Detergent drawers are notorious for harbouring mould.

• Remove the drawer completely.

• Soak in hot, soapy water with a splash of vinegar.

• Scrub all compartments using a toothbrush.

• Clean the drawer housing inside the machine using a cloth and a mild cleaning solution.

Step 4: Clean the Rubber Door Seal

Mould and bacteria often collect in the folds of the rubber door seal.

• Wipe the seal with a cloth soaked in white vinegar or anti-mould spray.

• Use a toothbrush to reach deep into the folds.

• Dry the area thoroughly to prevent further growth.

Step 5: Flush the Drain Hose

If you suspect a blockage or residue build-up:

• Unplug the washing machine and move it to access the rear.

• Disconnect the drain hose from the waste pipe or standpipe (have a bucket ready).

• Rinse the hose with hot water and flush with a white vinegar solution.

• Reattach the hose securely, ensuring it has a proper fall to avoid standing water.

When It’s More Than Just the Machine

If you've thoroughly cleaned the washing machine and the smell persists, the problem may lie in the property’s wider drainage system. Warning signs include:

• The smell is worse near the waste pipe or gully outside.

• Water drains slowly from the washing machine or backs up.

• Other nearby fixtures (e.g. sink or bath) also drain slowly or emit bad odours.

These symptoms may indicate:

• A partially blocked waste pipe

• Poor pipe gradient

• Rodent ingress or structural damage to the external drains

In such cases, a professional inspection using CCTV drain survey equipment is often the most effective way to diagnose the issue.

Preventing Washing Machine Drain Smells: Best Practices

To avoid recurring smells, routine maintenance is key. Preventative habits save time and reduce the risk of blockages.

1. Use the Right Amount of Detergent

Overuse of detergent leads to build-up. Always follow the dosage guidelines for your machine and local water hardness.

2. Leave the Door and Drawer Open After Every Wash

This allows moisture to evaporate and discourages the growth of mould and bacteria.

3. Run a Monthly Hot Wash

A regular hot cycle helps keep internal parts clean. Add white vinegar or a dedicated washing machine cleaner for best results.

4. Clean the Filter and Drawer Monthly

These areas are prone to build-up and should be part of a routine cleaning schedule.

5. Inspect the Drain Hose Annually

Ensure the hose is not kinked, crushed, or sagging. Reposition if necessary to maintain proper water flow.

6. Check External Drains for Obstructions

Inspect the gully or external drain that your machine feeds into. Remove debris and leaves regularly to avoid blockages.

Final Thoughts

A bad smell coming from your washing machine drain is not just unpleasant – it’s a sign that bacteria or waste is building up somewhere in your system. While most odours can be resolved with a deep internal clean, persistent or returning smells may point to a larger problem in the connected drain system.

If you’re based in Southampton or the surrounding areas and suspect your issue may be deeper than the appliance, GSB Drainage offers fast, no-dig diagnostic services to inspect and resolve drainage issues at the source.

Don’t let a foul-smelling machine affect your home. Tackle it early, clean thoroughly, and maintain regularly to keep your laundry and your drainage system fresh.