Why does my dishwasher smell?
Updated August 2026
A kitchen that gets a sour, swampy whiff every time the door opens is nearly always rotting food trapped in the dishwasher filter and sump, the low basin under the bottom spray arm where scraps collect. Pull the cylindrical filter, rinse it under hot water, and wipe the sump; that alone clears most odors for free. If the smell lingers or you find standing water pooled at the bottom, the trouble has moved downstream to grease or a drain clog, so work through the causes below in order.
Causes, most likely first
| Cause | How likely | The fix | Typical cost |
|---|---|---|---|
| Rotting food in the filter and sump | Most common | Twist out the bottom filter, rinse it under hot water, and scoop debris from the sump and around the spray arm. | Free |
| Grease and detergent film on the tub | Common | Run an empty cycle on the hottest setting with two cups of white vinegar in a bowl on the top rack. | $0–10 |
| Clogged or kinked drain hose | Common | Standing water at the bottom points here; clear the hose, the air gap, and the disposer knockout plug. | $0–150 |
| Fouled door gasket and edges | Occasional | Wipe the rubber seal, the door lip, and the detergent cup where black mold and gunk hide. | Free |
| Drain routed without a high loop | Occasional | Loop the drain hose up under the counter so dirty sink water cannot back-siphon into the tub. | $0–100 |
Check these first
- Twist out the bottom filter and check it for trapped seeds, bones, and labels; rinse until the mesh runs clear.
- Look for standing water in the sump after a cycle. A full inch of gray water means a drain problem, not just grime.
- Smell the sink drain next to the dishwasher; a shared, gunked-up disposer or air gap can send odor back up the hose.
- Run the hottest wash cycle empty with vinegar and see whether the smell is gone the next day.
- Check the door gasket and the plastic detergent cup for black mildew, and wipe them down with a little dish soap.
Prevent it next time
The smell is a cleaning-interval problem more than a broken part. Rinse the filter on a monthly schedule and the food that feeds the odor never gets a chance to rot. Add a hot vinegar cycle every month or two, and run a descaling cycle a few times a year in hard-water areas to strip the grease and mineral film that traps smells. A machine emptied of scraps and run hot regularly simply does not stink.
When to call a pro
Call a plumber or appliance tech when water still pools in the bottom after you have cleaned the filter and checked the hose, when the smell is sewage rather than sour food, or when the dishwasher will not drain at all. A drain-related service call runs $100–250, a new drain pump $150–350 installed. If the odor comes with a leak at the base or the machine also stops cleaning dishes, treat it as a drainage fault, not just a dirty tub.
Most of the causes above are maintenance problems wearing a disguise. OnOtto keeps the boring prevention on schedule so the 2 a.m. version doesn't happen.
Stop chasing symptoms, free for 30 daysFrequently asked questions
Why does my dishwasher smell like rotten eggs or sewage?
A sewage or rotten-egg smell usually means the drain, not the tub. The common causes are a drain hose that lacks a high loop, so sink water siphons back in, or a clogged air gap and disposer connection letting waste sit in the line. Bacteria in that trapped water produce the sulfur odor. Clear the air gap, confirm the hose loops up under the counter, and run the disposer before each wash. If it persists, a plumber should check the drain routing.
Does running vinegar and baking soda actually clean a dishwasher?
Yes, as a monthly reset, though it is not a substitute for pulling the filter. Place two cups of white vinegar in a bowl on the top rack and run the hottest cycle; the hot vinegar cuts grease and mineral film on the tub and spray arms. Follow with a cup of baking soda sprinkled on the bottom and a short hot rinse to deodorize. What vinegar cannot do is remove the solid food packed into the filter, so clean that first.
Is a smelly dishwasher a health risk?
The mold and bacteria behind the smell are rarely dangerous, but they are worth clearing. A warm, damp tub full of food residue grows mildew on the gasket and biofilm in the drain, which can pass a musty taste to dishes and bother allergy-prone people. None of it is an emergency. A monthly filter clean, a hot vinegar cycle, and leaving the door cracked open to dry between loads keeps the growth in check.