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Why Your Dishwasher Smells (and Why It Is Not the Same Problem as a Washing Machine)

Dishwasher smell is not the same problem as a stinking washing machine. The fix is the filter, the spray-arm holes, and the door-seal channel, in that order, and it takes about ten minutes.

By Smit Sharma August 6, 2026 6 min read
Open dishwasher with the lower rack removed showing the removable filter assembly on the floor of the machine.

A dishwasher smells for a specific reason, and it is almost never the reason the internet gives you. It is not limescale. It is not the drain hose. It is not something that will be solved by a lemon on the top rack or another sachet of salt. Nine times out of ten it is the filter at the bottom of the machine, and once you have looked into one that has not been touched in a year, you will not need convincing again.

I want to separate this from the washing-machine problem, because we have a piece on that already and readers keep conflating the two. A washing machine smells because a cool, damp drum full of detergent residue and biofilm grows a bacterial mat in the sump and the door seal. The fix there is a 90 degree service wash, cleaning the gasket, and running the machine hotter more often. A dishwasher is the opposite problem. It runs hot every time. What it collects is food, and food rots in the three places the water cannot reliably reach: the filter housing, the ends of the spray-arm holes, and the U-shaped channel at the base of the door seal.

What the smell actually is

Open a dishwasher after a two-day gap between cycles and sniff. If the smell is sour, slightly cheesy, faintly meaty, that is anaerobic bacteria eating trapped food solids. It is the same family of bugs that make a bin smell in August. This is not a hygiene panic. It is not going to poison anyone, because the wash cycle itself runs at 55-70 degrees Celsius and sterilises the load. But the residue between cycles smells, and every time you open the door to load a mug you get a small waft of it.

If the smell is more chemical, sharp, like drains, that is a different problem: a dry U-bend in the sink the dishwasher drains through, or a kinked waste hose. That one is worth ruling out early. Run the tap in the sink next to the dishwasher for thirty seconds. If the smell weakens, it was the trap, not the machine.

The filter, which is almost certainly the answer

Every domestic dishwasher made in the last fifteen years or so has a removable filter assembly in the base, under the lower spray arm. Bosch, Miele, Beko, Whirlpool, Hotpoint, all of them. The manufacturers assume you know this. Most people do not. Which? has repeatedly flagged that a majority of UK owners have never removed their filter, and I would guess the real figure is lower than the survey suggests.

Pull the bottom rack out. You will see a plastic assembly in the middle of the floor of the machine, usually a cylindrical mesh column sitting inside a flat perforated plate. It unscrews. Anticlockwise, quarter turn, sometimes half. Lift the whole thing out. The first time I did this on a machine that had been running for eighteen months without attention, what came out was, and I mean this literally, a warm slurry of what used to be food. Grey, tacky, smelling like a compost heap on a hot day. That was the smell.

How to actually clean it

  1. Take the assembly to the sink. Do not do this over the dishwasher, you will drop bits back in.
  2. Rinse under the hot tap. Most of the sludge lifts straight off.
  3. Use an old toothbrush and a bit of washing-up liquid on the fine mesh. Both sides. You are looking for translucent, not opaque.
  4. Check the cavity the filter came out of. There is usually a small amount of standing water and often a rogue olive stone or bit of eggshell. Fish it out with kitchen paper.
  5. Screw the filter back in, firmly. If it is loose the machine will not filter properly and you will be back here in a month.

Total time, ten minutes. This alone fixes most dishwasher smell problems permanently, provided you then do it every 4-6 weeks. I put a reminder in my phone. It is the single highest-value maintenance job in the kitchen.

The spray-arm holes, which nobody thinks about

If the filter is clean and the smell is still there, the next place to look is the spray arms. There are usually two, one under the bottom rack and one under the top. They spin, they have small holes, and the holes clog with a mixture of limescale and cooked-on food residue, particularly in hard water areas. In many UK cities the tap water sits around 100-250 mg/l calcium carbonate, which is moderately to properly hard, so this happens here.

Unclip the arms. They usually pop off with a firm pull upwards, or unscrew via a central nut. Hold each one up to a bright light. If some of the holes look partially or fully blocked, run a wooden cocktail stick or an unbent paperclip through each one. Not a needle, you will scratch the plastic and it will trap food faster next time. Rinse under the tap, replace, clip back on and check they still spin freely.

The door seal, the bit that keeps re-smelling

The rubber gasket around the door, and specifically the U-shaped trough at the bottom where the door meets the tub, collects a surprising amount of food. Bits of rice, coffee grounds, tomato skin. The water jets do not reach this area directly because it sits outside the wash chamber when the door is closed. Whatever gets in there stays there.

Pull the door open fully. Take a damp cloth and a bit of washing-up liquid. Wipe along the whole channel, top, sides, and especially the bottom lip. Peel the flexible edge of the seal back gently and wipe behind it. This is a two-minute job and it is the reason your machine still smells slightly even after you cleaned the filter last month.

What order to do things, and what to skip

Step Time Fixes what
1. Remove and clean filter 10 min ~70% of smells
2. Wipe door seal channel 2 min Persistent low-grade smell
3. Clear spray-arm holes 5 min Poor cleaning + smell
4. Hot empty cycle with 250 ml white vinegar in a mug, top rack 90 min (unattended) Residual film in pipework
5. Check sink U-bend if smell persists 1 min Drain-side, not machine

Things I would skip: lemon halves on the rack (they do nothing the wash cycle does not already do), branded dishwasher fresheners that clip to the rack (perfume, not cleaning), and any advice that starts with baking soda and vinegar together (they neutralise each other, you get salty water). A single empty hot cycle with a mug of white vinegar on the top rack is genuinely useful, once, after you have done the mechanical cleaning. Repeating it weekly is not.

When it is not the dishwasher at all

If you have done all of the above and the smell returns within a week, check the drain hose. It should rise in a loop to at least 400 mm above the floor before dropping to the waste connection under the sink. This is required by most manufacturer installation instructions, and if a plumber or the previous owner ran it as a flat horizontal, dirty sink water can siphon back into the machine and sit in the base. That produces a persistent, drain-adjacent smell that no amount of filter cleaning will fix. Cure is a plastic bracket screwed inside the cupboard to hold the hose in the correct high loop. Ten minutes, a screwdriver, done.

a family friend, who fixed white goods for a living for thirty years, said the most common call-out he got for smell was almost always resolved without opening the machine. Filter, seal, spray arms, hose loop. In that order.

Related reading

Frequently Asked Questions

Every 4-6 weeks for a household that runs the machine daily, or monthly to be safe. If you cook a lot with rice, pasta, or fatty foods, do it more often. A quick rinse takes two minutes once you are in the habit.

No. The hot cycle sterilises and cleans dishes, but it does not remove the food solids trapped in the filter or door seal. Those need to be physically taken out and rinsed. The smell will keep coming back until you do.

The dishes themselves are fine. The wash cycle runs at 55-70 degrees Celsius, which kills the bacteria producing the smell. The concern is the residue sitting in the machine between cycles, which is unpleasant but not a health risk.

Because trapped food has had five to ten days at room temperature to ferment in the filter and door seal, undisturbed by any cycle. Before going away, run an empty hot cycle and prop the door open. When you come back, clean the filter first.

They mask the smell with perfume, they do not clean anything. If you like the scent, fine, but they are not a substitute for pulling the filter out. If the underlying food residue is still there, the freshener runs out in a fortnight and the smell returns.

Senior Contributor

Smit Sharma

Smit Sharma writes and edits Repair Habit. He is not a licensed technician of anything. What he knows about repair he picked up the ordinary way: watching his father fix things around the flat rather than throw them away, spending two summers as an apprentice in a small electronics shop, and, once he had his own place, running through the mistakes himself on his own washing machine, kettle, chairs, and car. He is a working parent, a slow buyer of new things, and a slightly obsessive maintainer of the ones he already owns. He does not believe repairing your dishwasher makes you a better person. He believes it is often the cheapest and quietest response to a small problem, which is roughly all the philosophy this site carries.

105 articles written Contributor since 2021 Updated regularly

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