Why Does My Dishwasher Smell?
A smelly dishwasher is almost always caused by food debris, grease, or soap scum accumulating in areas that do not get properly rinsed during a normal cycle — the filter, the door seal, the spray arm holes, or the drain. A blocked or infrequently cleaned filter is the cause in the majority of cases and resolves with a straightforward clean. Persistent smells after cleaning suggest a drainage issue worth investigating.
Identifying the Smell
Different smells indicate different sources. Identifying which type you are dealing with is the fastest route to the right fix.
Standing water or a closed door
A musty, slightly stale smell when you open the door — even without any food odour — usually comes from standing water in the base of the tub combined with a closed door. Water that cannot evaporate between cycles creates a warm, damp environment where bacteria multiply. The fix is simple: leave the door slightly ajar after each cycle to allow the interior to dry fully. If the musty smell persists with the door left open, there may be water sitting in the drain or sump that is not draining completely.
Blocked or dirty filter
A sulphurous, rotten, or eggy smell is the most common dishwasher odour and almost always traces back to the filter. Food particles trapped in the filter decompose over days and weeks, producing hydrogen sulphide — the compound responsible for the rotten egg odour. Even if the filter looks clean from above, food debris compacted beneath the mesh or in the cylindrical inner section creates this smell. Remove, disassemble, and clean the filter thoroughly under hot running water with a soft brush. This resolves the smell in the majority of cases within one cycle.
Grease and residue on internal surfaces
A greasy, fatty, or sour smell without a strong food component indicates grease build-up on the door seal, the inner walls, or in the spray arm channels. Low-temperature cycles — eco and quick programmes — do not always dissolve grease effectively, particularly from heavily soiled loads. Grease accumulates progressively and eventually reaches a level where it smells during every cycle. Run a hot 60°C or 65°C cycle monthly without any dishes to burn off grease residue, and wipe the door seal and inner rim after the cycle.
Detergent residue build-up
A soapy or chemical smell that is noticeable when the door is opened — particularly after eco or cold cycles — indicates detergent residue not being fully rinsed away. This happens most often when using too much detergent, when the water is very soft and the detergent dose has not been adjusted, or when cycles do not reach a high enough temperature to fully dissolve the tablet or powder. Reduce the detergent dose and ensure rinse aid is topped up — rinse aid helps the final rinse clear detergent residue from surfaces and dishes.
Drainage issue or drain hose problem
A smell of sewage or drains — distinct from food odour — suggests that gases from the household drain are entering the dishwasher through the drain connection. This can happen if the drain hose has no high loop or is not correctly connected to a standpipe, allowing drain gases to flow back into the tub. It can also indicate a blocked or slow drain causing waste water to sit in the hose. Check that the drain hose has a high loop under the counter — the hose should rise to counter height before dropping to the drain connection. If the connection is correct and the smell persists, call a plumber to check the drain.
How to Clean a Smelly Dishwasher
Work through this sequence in order — the filter is the most common cause, so start there. Most dishwasher smells clear completely after steps one through four.
- 1
Remove and clean the filter
The filter assembly is in the base of the tub — usually a cylindrical mesh section that twists out, and a flat plate filter beneath it. Remove both. Rinse under hot running water and use a soft brush to clear any compacted food from the mesh and the cylindrical section. Do not use abrasive scourers — they damage the mesh. Replace both sections securely. This single step resolves the smell in the majority of cases.
- 2
Wipe the door seal, inner rim, and walls
Run a damp cloth around the inside of the door frame and along the rubber door seal, paying close attention to the folds at the bottom where the seal meets the tub. This area traps food particles and moisture that the wash cycle does not reach. Wipe the inner walls and base of the tub as well. A mild solution of warm water and washing-up liquid on the cloth is effective — rinse the cloth and wipe again to clear any residue.
- 3
Check and clear the spray arm holes
Remove the spray arms (they usually unclip or unscrew from their mounting positions) and hold them up to the light to check for blocked holes. Food debris and limescale block individual jets over time, reducing cleaning effectiveness and allowing debris to sit in the arm. Use a toothpick or thin skewer to clear any blocked holes, then rinse under hot water and replace.
- 4
Run a hot vinegar cycle
Place a dishwasher-safe bowl or cup containing 250ml of white distilled vinegar on the top rack. Run the hottest programme available — typically 65°C or 70°C — with no dishes and no detergent. The vinegar breaks down grease deposits, mineral scale, and bacterial residue on interior surfaces and in the pump and drain. The smell of vinegar during the cycle is normal and clears completely once the cycle finishes.
- 5
Follow with a bicarbonate of soda cycle
Sprinkle 200g of bicarbonate of soda across the base of the empty tub and run a short hot cycle. Bicarbonate neutralises acidic odours and removes any remaining smell from the vinegar cycle. Leave the door slightly ajar after the cycle to allow the interior to cool and dry with full air circulation. The dishwasher should now be odour-free.
Keeping It Fresh — Prevention
Clean the filter every 2 to 4 weeks
This is the single most effective prevention measure. A filter cleaned regularly never accumulates enough decomposing food to produce a smell. Two minutes under hot water every few weeks is all it takes. Make it part of the same routine as wiping down the kitchen.
Scrape plates before loading — do not pre-rinse
Scrape large food pieces into the bin before loading. Do not rinse plates under the tap before loading — modern dishwashers with soil sensors need some residue to calibrate the cycle correctly. What you want to prevent is large food pieces reaching the filter, not all food residue.
Run a 60°C cycle at least once a week
Eco and quick cycles at 45°C do not fully dissolve grease or kill bacteria. If most of your washing is done on short or eco programmes, run a full 60°C cycle once a week — even on a partial load — to clear accumulated grease and keep bacteria in check.
Leave the door ajar after every cycle
A sealed, damp interior is the ideal environment for bacteria. As soon as the cycle finishes, prop the door open a few centimetres. This allows steam and moisture to escape, the interior to cool, and air to circulate. Most new dishwasher models open the door automatically at the end of the cycle for exactly this reason.
Keep rinse aid topped up
Rinse aid helps water sheet off dishes and interior surfaces during the final rinse, reducing the amount of food-containing water left on surfaces as the machine drains. It also reduces mineral spotting. A dishwasher running without rinse aid leaves more residue on every surface after every cycle.
Run a monthly maintenance cycle
Once a month, run an empty hot cycle with a dishwasher cleaning tablet or the vinegar method described above. This prevents the gradual build-up of grease and limescale that creates persistent smells, and keeps the pump, drain, and internal components clear of residue between regular use.
CATA’s dishwasher range includes models with self-cleaning filters and auto door-opening at the end of the cycle to reduce moisture retention. For a full guide on dishwasher running costs and efficiency, see how much water a dishwasher uses per cycle — understanding cycle selection also affects how much grease residue accumulates between cleans.
Common questions answered
Why does my dishwasher smell even though it looks clean inside?
The most common cause is the filter — even when the interior looks clean, the filter can hold compacted food debris in the inner cylindrical section that is not visible from above. Remove and fully disassemble the filter, then check. The drain area and spray arm holes are the other likely sources not visible on a quick visual inspection.
Is it normal for a dishwasher to smell after a cycle?
A mild, clean-but-damp smell immediately after a hot cycle is normal — this is steam condensing on the interior surfaces. A bad smell after a cycle is not normal and indicates food residue, grease build-up, or a drainage issue. The type of smell points to which problem to address first.
Can I use dishwasher cleaner tablets instead of vinegar?
Yes — proprietary dishwasher cleaning tablets are effective and convenient. Follow the manufacturer’s instructions, which typically involve placing the tablet in the base of the empty tub and running a hot cycle. They clean the drum, pump, and internal components in the same way as the vinegar method, and many include a descaling agent as well.
My dishwasher still smells after cleaning. What next?
Check the drain hose routing — if it has no high loop under the counter, sewage gases from the household drain can enter the tub. Confirm the door seal is intact with no torn or compressed sections. If both are fine and the smell persists after a thorough clean, a plumber or appliance engineer should inspect the drain connection and pump for blockage or fault.
Explore More Kitchen Advice & Buying Guides
Browse our latest articles covering appliance tips, energy-saving advice, and expert guidance – designed to help you choose, use, and get the most from your kitchen appliances.
