Mold in a Dishwasher: Where It Hides and How to Clean It Without Wrecking the Tub (2026)

A Warm, Wet Box With a Food Supply

A dishwasher is the most mold-friendly appliance in the kitchen: hot, humid, sealed between loads, and fed a steady diet of food particles. The colony grows where the wash cycle does not reach — the drain filter at the bottom, the folds of the door gasket, the inside of the spray arms — and announces itself as a musty breath when the door opens, a film on glassware, or black spots along the rubber seal.

It is a cleaning-and-habits problem, not a house-mold problem, and it takes an hour to fix.

Where It Hides

Cleaning It

EPA's advice for mold on hard surfaces — scrub with detergent and water, then dry — is the whole method here; a dishwasher is all hard surfaces. The only real question is which cleaner, and the answer depends on the tub.

1. 1The filter. Under the lower spray arm; a quarter turn releases it on most machines. Most people have never removed it. Scrub it with hot water and dish soap, brush the mesh clear, and look into the sump it came out of — wipe that too.
2. 2The gasket. Pull the rubber seal back gently and wipe every fold and the bottom lip with warm soapy water or diluted vinegar. An old toothbrush for the corners, which is where the black spots sit.
3. 3The spray arms. They lift off. Rinse under the tap and clear each jet with a toothpick; blocked jets are why the top rack has been coming out dirty.
4. 4The cycle. Hottest, longest program, empty, with a dishwasher cleaner — or a cup of white vinegar in a bowl on the top rack. Vinegar kills much of what grows in a dishwasher and is safe on stainless.
5. 5Dry. Wipe the rim and gasket, and leave the door cracked open.

On bleach: it kills mold, and it works on hard surfaces — but it corrodes stainless steel, and most dishwashers made in the last fifteen years have a stainless tub, stainless racks and a stainless heating element. Bleach belongs in a plastic-tub machine only, diluted, and never in the same cycle as vinegar (the combination releases chlorine gas). If you are not sure what the tub is made of, use vinegar or a dishwasher cleaner.

Keeping It Away

• Scrape, don't pre-rinse. Modern detergents need some food to work on, but chunks go to the filter and rot. Scrape plates; skip the rinse.
• Filter monthly. Two minutes under the tap. This one habit prevents nearly all dishwasher mold.
• Crack the door after the cycle. The tub dries instead of steaming in a sealed box. Machines with an auto-open dry setting do this for you.
• Run it hot and run it full. Eco cycles that never reach a high temperature leave residue; a machine that sits three days between runs with dirty dishes inside grows a colony on them.
• Check the air gap. The small chrome cylinder by the faucet, if you have one — a blockage there holds stagnant water and a smell no cleaning fixes.

The Smell That Survives Everything

A musty smell after a full cleaning, an open door and a clear air gap is usually the drain hose: a low loop holding stagnant water, or a partial clog. Pull the machine forward, check that the hose rises to a high loop under the counter before it drops to the drain, and flush it. And if the smell is not from the machine at all — a cabinet that is damp, a floor that is soft in front of the dishwasher — a leak at the supply line or the door seal has been wetting the cabinet base, and that is a water damage problem, not a cleaning one.

Bottom Line

Filter, gasket, spray arms, hot cycle, door open. Vinegar or a dishwasher cleaner in a stainless machine; bleach only in a plastic one, and never together. Dishwasher mold is the filter nobody has cleaned and the door nobody leaves open — and both take a minute once you know they exist.