Why Your Dishwasher Smells and How to Fix It

Each odor points to a different spot. Read the smell first, then check the place it names before you start scrubbing the whole tub.

A new machine can give off a temporary odor as manufacturing residues heat up. A plastic smell lasts roughly two weeks, a petroleum-like smell from sound-deadening material runs about four to six weeks, and a varnish-like smell fades in about a month. Running a few cycles with detergent speeds it up. It is not a defect.

A small amount of water in the filter well and sump between cycles is normal, because it keeps the seals wet. An inch or more standing in the tub is not, and that points to a drainage problem. A persistent smell in an otherwise working machine is not normal either: manufacturers' guidance is consistent that a dishwasher which cleans properly should not retain odor. Persistent odor means something is trapped or the drain path is wrong.

A manual-clean filter

This is the most common cause. Many US machines use a manual filter the owner is supposed to rinse, while others use a self-cleaning filter with a hard-food disposer that needs no routine cleaning. Owners often don't know which they have. Locate it, usually a quarter turn to release the upper section, then lift out the lower one. Rinse it under running water with a brush, reinstall it and lock it. Never run the machine with the filter loose.

Food in the sump, tub bottom, door edges and dispenser

Food that reaches the machine has to go somewhere. Scrape dishes rather than pre-rinsing everything, and wipe the tub bottom, the door edges and the dispenser where crumbs collect.

Grease and soap-scum film

A film on the tub walls, racks and door traps food and goes rancid. Too much detergent, or detergent that doesn't fully dissolve, makes it worse. Wipe the surfaces and use the amount the detergent label gives for your water hardness.

Clogged spray-arm jets

Food and mineral bits block the holes, so the arm can't rinse the tub and washing performance drops too. Lift the arm off and clear the holes with a toothpick or a paper clip.

Mold in the door gasket fold

The fold and the door's bottom edge are the most-missed spots. Wipe them. Recurring mold can mean the machine isn't reaching a high enough wash temperature, and that is a service call, not a cleaning problem.

Standing water

A partial drain clog, a kinked drain hose, a failed drain pump or valve, or a knockout plug left in the disposal inlet after a new install all leave water behind. Clear the filter and the hose first, then check the disposal.

A drain path problem

A missing high loop, a clogged air gap or a hose connected downstream of the P-trap lets sewer gas into the machine. This is the sewage smell, and it has its own section below.

Hard-water mineral scale

Scale harbors biofilm and dulls the wash. In hard-water areas the machine needs a descaler a few times a year.

Infrequent use and dirty dishes stored inside

A machine run less than about once a week, or used as a dirty-dish cupboard, grows mildew. Run it at least weekly and use a rinse-only cycle for partial loads.

Low water temperature

If the water heater is set too low, the wash doesn't get hot enough to keep biofilm in check. Manufacturers' guidance puts the target around 120 to 149°F.

The order matters, because cleaning the tub before the filter just spreads the mess back around.

1. Empty the machine and pull the bottom rack.
2. Remove and rinse the filter, then scrub the filter well and sump with a brush. Unplug the machine before reaching into the sump.
3. Wipe the tub walls, door edges, dispenser and the gasket fold.
4. Clear the spray-arm jets.
5. Run a deep-clean cycle: a citric-acid dishwasher cleaner, or the vinegar-then-baking-soda method in two separate cycles.
6. Check the drain path: hose routing, air gap and disposal.
7. Dry it out: leave the door ajar between uses, wipe the tub and use a dry cycle.
8. Fix the habits: scrape, don't store dirty dishes, run weekly, don't overload.

The cadence that resolves the contradictions across sources: rinse the filter after every load or weekly, wipe the gasket weekly, run a deep-clean cycle monthly, and descale a few times a year in hard water.

White vinegar works for occasional deep cleans and for wiping the gasket. It is acidic, so using it every cycle can wear on the machine: treat it as an occasional treatment, not a routine. Baking soda deodorizes and helps lift film, and it goes in a separate cycle from vinegar, because together they just foam and cancel out.

Citric acid, as a powder or in a citric-acid dishwasher cleaner, is the best choice for hard-water scale and a good monthly deep clean. Skip bleach on stainless steel. If you use it at all, dilute it heavily and run a rinse cycle afterward; a sanitize cycle or citric acid is the safer route. Never mix bleach with vinegar or ammonia, which gives off toxic gas.

The sewage or wet-dog smell is usually sewer gas backing up through the drain hose, not a dirty dishwasher. The hose must loop high, at least 20 inches above the finished floor or up to the underside of the counter, before it connects to the disposal or drain. Manufacturers and plumbing code both require this high loop, and its stated purpose includes keeping odors from backing up into the machine.

The hose must also connect upstream of the P-trap, never downstream, because downstream lets sewer gas straight into the dishwasher. An air gap on the sink, common in some regions, can clog; clean it with a bottle brush. Check the garbage disposal and sink drain too, since they share the drain path and a smelly disposal can make the dishwasher smell. After a new disposal install, confirm the knockout plug was removed.

If the smell is sewage and the filter, tub and gasket are clean, check the hose routing and the disposal before calling anyone. If the routing is correct and the smell persists, it's a plumbing problem, so you need a plumber rather than an appliance technician.

Built-in 24-inch and slim 18-inch

Same filter design and same causes. The slim 18-inch uses less water per cycle, so film builds up a little faster if the filter isn't rinsed.

Freestanding

Same as a built-in: the filter, gasket and drain path are where the smell starts.

Portable on wheels

These connect to the faucet by hose. Water can sit in the internal tank and in the faucet adapter hose between uses, and there's no high loop in the same sense. Drain and dry the hoses, and don't store the unit sealed up while damp.

Compact countertop

A small tank drains into the sink. Empty and dry the tank after each use, because the small water volume means a little trapped food goes a long way.

Commercial and undercounter

Same principles, higher use, so filter cleaning moves to daily.

Odor comes back when the routine lapses, so put the jobs on a schedule you'll keep.

Call a technician for a burning or electrical smell (stop the cycle, unplug the machine and don't run it), water on the floor, a cracked gasket or latch, drainage that doesn't improve after clearing the filter and hose, and recurring mold that suggests the wash temperature is too low. Call a plumber for a sewage smell that persists after the drain routing is verified.

Consider replacing when the machine is around a decade old and the odor comes with failing wash performance or repeated repairs. Odor alone is rarely a reason to replace a dishwasher.