Mould in Your Dishwasher? How to Clean It and Prevent it from coming back

You open the dishwasher expecting clean dishes, but instead find a musty odour, dark spots around the seal, or slimy buildup near the filter. If you are here looking for a practical answer, the good news is that you may not need a new appliance or a cupboard full of harsh chemical nasties.

The best approach is to remove visible mould by hand, clean the places where food and moisture collect, then run an empty machine-cleaning cycle. The order matters. A dishwasher cleaner can tackle hidden buildup inside the dishwasher, but it cannot replace scrubbing visible growth from the filter, seal and door edges.

Quick answer: Empty the dishwasher, remove and wash the filter, clean the door seal and drain area with warm soapy water, rinse and dry the surfaces, then run a model-approved dishwasher cleaner through the empty machine. Never mix bleach, vinegar, baking soda or other cleaning products.

The US EPA recommends scrubbing mould from hard surfaces with detergent and water, then drying the surfaces completely.

First, make sure it is mould

Not every black mark or cloudy film is mould. Grease, food sludge, detergent buildup, and hard-water minerals collect in many of the same parts of the dishwasher.

Colour alone cannot identify a mould species. Treat suspicious growth as something to remove rather than trying to identify it from a photo.

What causes mould in a dishwasher?

A dishwasher regularly combines warmth, water droplets and small amounts of food. When food particles collect in the filter and moisture remains around the seals, they create the damp, dirty conditions that allow mould and bacteria to grow.

Poor ventilation and trapped residue can keep the dishwasher damp enough for mould and bacteria to grow or return.

Common causes include:

• A dirty dishwasher filter
• Grease and food around the drain
• Moisture behind the dishwasher door seal
• Poor ventilation after a wash cycle
• Standing water caused by a drainage problem
• A damaged seal, hose or another source of leaking water

The hot wash does not reach every surface equally. Mould in the dishwasher may remain around the door edge, beneath the seal or outside the main spray path. This is why a normal wash cycle may not remove growth around the seal and door edges.

Is mould in the dishwasher dangerous?

There is no need to panic over every dark mark, but visible mould should not be ignored. The CDC explains that mould exposure can irritate the eyes, skin, nose, throat or lungs in some people. People with asthma, mould allergies, chronic lung conditions or weakened immune systems may be more sensitive.

Anyone in a higher-risk group should avoid disturbing extensive growth. Ask another person to clean it or seek professional advice when the affected area is large, keeps returning or sits inside an inaccessible part of the appliance.

What you need

• Household cleaning gloves
• A soft cloth or non-scratch sponge
• A soft toothbrush or small cleaning brush
• Warm water
• Dishwashing detergent dissolved in the water
• A clean towel
• A torch/light
• Dishwasher Cleaner Tablet

Before you start: Empty the machine, switch it off, and let hot parts cool before reaching into the base. Check the appliance manual before using any cleaner.

How to clean mould from a dishwasher

1. Empty the dishwasher

Remove the dishes, cutlery basket and bottom rack. Check for scraps, labels, broken glass and anything that may block water circulation.

Only remove parts covered by the appliance manual. Do not unscrew fixed covers or reach into the pump.

2. Remove and clean the dishwasher filter

The filter usually sits below the lower spray arms. Turn and lift it out according to the manual. Take a photo first if you are unsure how the pieces fit together.

Remove loose food, then scrub the filter gently in your prepared soapy water. Use the toothbrush around the mesh and joins. Rinse well under clean water.

Avoid wire brushes and abrasive pads because they can damage the filter.

3. Clean the dishwasher door and seal

The dishwasher door, lower edge and seal are easy to miss because they may sit outside the main spray area.

Dip a cloth into the prepared water and wipe both sides of the seal, the lower door lip, corners and detergent dispenser. Use a soft toothbrush in narrow joins.

Do not pull or stretch the seal, and keep excess water away from the latch and controls.

4. Inspect the drain area

Remove visible debris from around the drain and filter well. Use a torch so you can see clearly.

A small amount of clean water in the filter well may be normal for some machines. Dirty standing water across the dishwasher floor may indicate a blocked filter, drain hose or plumbing issue.

Do not keep adding cleaner when the dishwasher is not draining. Check the manual or arrange appliance service.

5. Scrub the reachable interior

Wipe the interior walls, rack tracks and other hard surfaces where you see mould or grime. Scrub gently with the dissolved sheet solution, then wipe again with clean water.

Rinse the cloth often and dry the cleaned surfaces with a towel before replacing the filter and racks.

6. Run an empty cleaning cycle

Once the visible mould is gone, use an approved machine cleaner to tackle residue in the spray arms, pipes and other water-contact areas.

Our Dishwasher Cleaner Tablets help remove grease, food residue, detergent buildup, odours and mineral deposits from inside your dishwasher. This can support mould prevention by removing the grime it feeds on, but the tablet is not a substitute for manually cleaning visible growth.

Clean the filter first. Place one tablet in the bottom of the empty dishwasher and run the cycle according to the product directions and appliance manual.

7. Let the appliance dry

When the cycle ends, check the filter area and door edges again. Wipe away remaining water droplets.

Leave the dishwasher door slightly open where this is safe and permitted by the manufacturer. Better ventilation and drier surfaces make it harder for unwanted mould and bacteria to return. Moisture control is a central part of preventing mould from growing again.

What about vinegar, baking soda or bleach?

Many online tips suggest putting a cup of white vinegar in a dishwasher-safe container on the top rack, sprinkling baking soda on the bottom, or using bleach to disinfect the machine.

Do not combine these methods. Vinegar can affect some seals or internal parts, depending on the model. Baking soda and vinegar react with each other, so using them together does not create a stronger cleaner.

Follow the appliance manual and use one cleaning method at a time. A product designed for dishwasher maintenance gives clearer dosing instructions than a homemade mixture.

Tips to prevent mould returning

Keeping a frequently wet appliance completely mould-free cannot be guaranteed, but regular maintenance can help prevent mould growth:

• Scrape large food scraps (only) from each dish before loading.
• Check the filter when dishes feel gritty, or the dishwasher develops an odour.
• Clean the seal and lower door edge when buildup appears.
• Keep the dishwasher from sitting closed and moist for long periods.
• Use ventilation and keep the surfaces inside as dry as practical.
• Investigate standing water, damaged rubber parts, or leaking water.
• Run a maintenance cleaner according to its directions.

For a wider routine covering the filter, spray arms, seals, drain and interior, follow our step-by-step guide to cleaning your dishwasher.

When cleaning is not enough

You might need professional help if repeated cleaning doesn't help. This can happen. You can arrange appliance or plumbing help when:

• Mould returns within a few days
• Water remains across the bottom
• A sewage-like or musty odour persists
• The door seal is split or loose
• The machine leaks or displays an error
• Dishes remain wet after every cycle
• Growth appears inside a hose, pump or inaccessible cavity

Start by cleaning the filter and checking the manual. If you cannot identify the moisture source safely, stop repeating wash cycles and have the appliance inspected.

The best order for tackling mould

Start with the areas you can reach. Remove the filter, scrub visible growth, rinse the surfaces and dry them. Then use our dishwasher cleaner for hidden buildup inside the machine.

Finish by addressing the cause. A clean filter, working drain, intact seal, and enough drying time will do more for preventing mould than repeatedly running another hot cycle.