A dishwasher that smells bad — whether it’s a rotten egg odour, a musty mildew smell, or a sour, drain-like stench — is one of the most common dishwasher complaints homeowners have. The problem isn’t the machine malfunctioning; it’s organic material accumulating in areas that don’t get cleaned during normal wash cycles, providing a growing environment for bacteria and mould.

This guide identifies every source of dishwasher smell, how to eliminate each one, and how to prevent the odour from coming back.

Why Dishwashers Develop Bad Smells

A dishwasher runs hot water and detergent through its interior every cycle — so why does it smell? Because there are several areas inside a dishwasher that the wash water doesn’t reach effectively: the interior of the door, the filter, the spray arm interiors, the gasket around the door, and the drain hose. Food residue, grease, and standing water in these areas decompose over time, producing bacteria that cause odour.

The smell is usually at its worst when you first open the door at the start of a cycle (before hot water and steam have time to freshen things) or when you open the door after the machine has been sitting unused for a day or two.

Source 1: The Filter

This is the number one cause of dishwasher smell. The manual filter at the bottom of the tub catches food particles to prevent them from recirculating, but those caught particles decompose inside the filter over time — particularly if the filter hasn’t been cleaned in weeks or months. A dirty filter doesn’t just smell bad; it also degrades cleaning performance.

How to clean it:

Remove the lower spray arm (twist or pull off) and then unscrew or lift out the filter assembly.
Take both parts (the cylindrical mesh filter and the flat mesh plate beneath it) to the sink and rinse under warm running water.
Use a soft brush to scrub away any slimy residue — the slime is a biofilm of bacteria and is the primary odour source.
Clean the filter at least monthly for average-use households.

Source 2: The Door Interior and Gasket

The inside of the dishwasher door — particularly the lower interior panel — doesn’t get hit by the spray arms and accumulates a film of grease and food splatter over time. The rubber door gasket (the seal around the door opening) also collects food debris and moisture in its folds, providing an ideal environment for mould growth.

Wipe the door interior with a damp cloth dipped in a mixture of white vinegar and water.
Use a toothbrush or small brush to clean along the door gasket folds — pay particular attention to the bottom section where debris settles.
Do this monthly as part of a cleaning routine.

Source 3: The Spray Arm Interiors

Water travels through the spray arms during every cycle, but the interior of the arms can accumulate grease, limescale, and small food particles that aren’t flushed out. This buildup decomposes and contributes to odour — particularly from the lower arm which sits closest to the filter area.

Remove the spray arms and rinse them under warm running water.
Soak in a mixture of warm water and white vinegar for 15–20 minutes to dissolve mineral deposits.
Clear any blocked jets with a toothpick before reinstalling.

Source 4: The Drain Hose

The drain hose that carries wastewater from the dishwasher to the drain can develop grease buildup inside, particularly if the machine drains into a garbage disposal that also processes oily food waste. Bacteria in the drain hose produce a sour, drain-like smell that you’ll notice most when the dishwasher is idle.

Run a full cycle with a dishwasher cleaning tablet or a cup of white vinegar placed in the bottom of the tub — this flushes the drain hose.
If the smell is drain-like and concentrated near the back of the machine or under the sink, the drain hose is the most likely source.
Check that the drain hose makes a high loop before connecting to the drain — this prevents wastewater from siphoning back into the machine between cycles.

Source 5: A Clogged or Infrequently Used Machine

Dishwashers that sit unused for extended periods can develop stagnant water in the sump area (the lowest point of the tub) and in the pump housing. This stagnant water quickly becomes odorous. Running the machine at least every few days — even with a short rinse cycle — prevents stagnant water buildup.

How to Deep Clean a Smelly Dishwasher

When the smell is bad and routine cleaning isn’t enough, a full deep clean addresses all sources at once:

Remove and soak the filter and spray arms in white vinegar solution.
Wipe down the door interior, gasket, and tub walls with a vinegar-dampened cloth.
Place a dishwasher-safe bowl filled with 2 cups of white vinegar on the bottom rack.
Run a hot cycle (hottest setting) with the bowl of vinegar — no detergent. The vinegar circulates through the machine and drain hose, breaking down grease and killing bacteria.
After the cycle completes, sprinkle 1 cup of baking soda across the bottom of the tub and run a short hot cycle. This neutralises any remaining odour.

Our guide on getting dishes fully dry in the dishwasher covers related habits that also help prevent odour — particularly around rinse aid use and leaving the door ajar after cycles, which allows moisture to evaporate rather than sitting inside the machine.

Preventing Dishwasher Smell Long-Term

Clean the filter monthly — this single habit prevents the majority of dishwasher odour problems.
Scrape plates thoroughly before loading — large food deposits overwhelm the filter quickly.
Leave the door cracked open after a cycle completes so the interior dries.
Run a vinegar cleaning cycle monthly.
Use a quality rinse aid — it helps water sheet off surfaces cleanly, leaving less residue behind.

When the Smell Is a Sign of a Leak

A smell that is mouldy or musty — and seems to be coming from under the machine or from the cabinet below — may indicate a slow leak that’s keeping the area under the dishwasher damp. Check under and around the machine for water stains or moisture. Our detailed guide on fixing a leaky dishwasher covers every type of dishwasher leak and how to address each one.

When to Call a Professional

Dishwasher odour is almost always a cleaning issue, not a mechanical one. But if you’ve thoroughly cleaned all components and the smell persists — particularly a sewer or sulphur smell that isn’t present in any other drain in the house — there may be a plumbing issue with the drain connection that a plumber should inspect.

North Vancouver Appliances handles dishwasher repairs and maintenance across the North Shore. Visit our dishwasher repair page for service.

If you’re also seeing white film on your glasses and dishes, that’s a separate hard water issue worth addressing at the same time as the smell.

Why Your Dishwasher Smells Bad (And How to Fix It)