A dishwasher that smells like mildew, rotting food, or stagnant water is one of the more unpleasant kitchen problems — especially when you’re counting on it to clean your dishes. The irony is real: the appliance designed to clean your things can itself become a source of foul odours. And left unaddressed, those odours transfer to your dishes, glasses, and cutlery.
Tri-City Repairs helps homeowners in Coquitlam, Port Coquitlam, and Port Moody keep their kitchen appliances in top condition. Here’s a complete guide to why dishwashers smell bad and exactly how to fix it.
Why Do Dishwashers Develop Odours?
Dishwashers create an ideal environment for bacteria and mould: warm, enclosed, and frequently damp. Between cycles, food residue trapped in the filter, door seal, spray arms, and walls of the tub starts to decompose and produce odour-causing bacteria. Hard water deposits and detergent buildup compound the problem by creating rough surfaces where bacteria cling and multiply.
The Main Odour Sources — and How to Clean Each One
1. The Filter (Most Common Cause)
The dishwasher filter sits at the base of the tub and catches food particles to prevent them clogging the drain pump. If it’s never cleaned, it becomes a decomposing food trap — and the smell can be significant. Many homeowners don’t know their dishwasher even has a removable filter.
How to clean it: Remove the bottom rack. Twist and lift the filter out (it usually requires a quarter-turn to unlock). Rinse it under hot running water and scrub with a soft brush and dish soap. Rinse thoroughly and reinstall. Do this monthly.
2. The Door Gasket
The rubber seal around the door edge traps moisture and food particles in its folds — especially at the bottom, where debris accumulates. Mould and mildew thrive here.
How to clean it: Use an old toothbrush dipped in a solution of equal parts white vinegar and warm water. Work your way around the entire gasket, paying special attention to the bottom fold. Wipe dry with a cloth and leave the door slightly ajar after cleaning to let it air dry.
3. The Spray Arms
The rotating spray arms distribute water throughout the dishwasher. Their small holes clog easily with mineral deposits and food debris, reducing washing effectiveness and creating pockets where bacteria grow.
How to clean them: Most spray arms can be removed by unscrewing a central nut or simply pulling them off. Rinse under running water, then use a toothpick or thin wire to clear each hole. Soak in white vinegar for 20 minutes for stubborn mineral buildup, then rinse. Reinstall.
Blocked spray arms don’t just cause odours — they cause poor cleaning results too. See Why Is Your Dishwasher Taking Too Long to Finish a Cycle? for more on how reduced water flow affects cycle performance.
4. The Drain and Drain Hose
If water isn’t fully draining after each cycle — even a small amount sitting at the bottom of the tub — it stagnates between uses and generates powerful odours. The drain hose that leads to your sink drain or garbage disposal can also accumulate grease and food residue over time.
How to check: After a completed cycle, look at the bottom of the tub. There should be no standing water. If you see any, a drain issue needs attention. See our detailed guide: Dishwasher Not Draining: What’s Causing It and How to Fix It.
5. The Tub Interior
Grease, detergent film, and mineral deposits build up on the stainless steel or plastic tub walls over time. They’re not always visible, but they harbour bacteria and produce a stale, musty smell.
How to clean it: Place a dishwasher-safe bowl or cup filled with 2 cups of white vinegar on the top rack. Run a hot water cycle with no dishes and no detergent. The vinegar steam dissolves grease film and mineral deposits throughout the tub, spray arms, and drain. Follow with a second cycle with half a cup of baking soda sprinkled in the bottom of the tub — this deodorises and lifts any remaining residue.
Full Deep Clean Routine
- Remove and scrub the filter thoroughly.
- Clean the door gasket folds with vinegar solution.
- Remove, clear, and soak the spray arms.
- Wipe down the door interior and tub walls with a damp cloth.
- Run a hot vinegar cycle (no dishes).
- Run a baking soda cycle (no dishes).
- Leave the door ajar for 30 minutes after to ventilate.
Do this full routine every 1–3 months depending on how heavily you use the dishwasher.
Preventing Dishwasher Odours
- Clean the filter monthly — this alone prevents the majority of odour problems.
- Leave the door slightly open after cycles — allows moisture to escape and the interior to dry.
- Scrape (don’t pre-rinse) dishes — large food chunks should be removed but a light residue is fine; the detergent needs something to work against.
- Use the right amount of detergent — too much leaves a film that feeds bacteria.
- Run the dishwasher regularly — infrequent use lets water sit stagnant in the sump and drain areas.
If residue on your glasses is also an issue alongside the smell, Dishwasher Leaves a Film on Glasses addresses the water chemistry and detergent factors that cause cloudy glassware.
When Odour Signals a Bigger Problem
A persistent smell even after a thorough deep clean may indicate water is remaining in the sump due to a partial drain pump failure or a drain hose issue. A sewer gas smell (rotten egg) points to a plumbing issue with the drain connection rather than the dishwasher itself. In either case, a technician visit is warranted.
Call Tri-City Repairs
If cleaning doesn’t resolve the smell, or if you suspect a mechanical issue is causing water to sit in the machine between cycles, we’re here to help. Call (604) 359-5952 or visit tricityrepairs.ca to book a service call in Coquitlam, Port Coquitlam, or Port Moody.