The smell comes from trapped food, standing water, and bacteria in your drain line
A sewer smell from your dishwasher means something is rotting inside the machine or in the drain line connected to it. The most common culprit is food debris trapped in the filter, spray arm holes, or the drain pump — places where water sits between cycles. Bacteria and mold grow in that standing water and produce hydrogen sulfide gas, which smells exactly like sewage.
The second most common cause is a clogged drain hose or a backup in your home's main drain line. If water cannot flow out freely, it pools inside the tub and starts to decompose. A third possibility is a broken or missing air gap — a small device on your counter or sink that prevents dirty water from flowing backward into the dishwasher from the drain.
The good news is that most of these problems are fixable without calling a repair person, and the fix usually costs nothing or under twenty dollars.
Key Takeaways
- Clean the filter basket at the bottom of the tub first — this is where most food debris collects and begins to smell.
- Run a cleaning cycle with white vinegar or a commercial dishwasher cleaner to kill bacteria and break down buildup in the spray arms and drain pump.
- Check the drain hose under your sink for kinks, clogs, or improper installation; it should slope downward toward the drain.
- If the smell persists after cleaning, the clog may be in your home's main drain line, which requires a plumber.
Clean the filter basket and drain area
The filter basket sits at the bottom center of your dishwasher tub. Remove it by twisting or lifting — the method depends on your model, but the manual will show you. Rinse it under hot running water and scrub away any visible food, grease, or slime with an old toothbrush or soft cloth. This single step solves the problem in roughly half of all cases.
While the filter is out, look into the drain area below it. You may see a small drain pump with a rubber seal. Wipe around this area with a damp cloth to remove any debris or buildup. Do not force anything or take the pump apart unless your manual explicitly tells you how. Reassemble the filter and run an empty cycle to rinse.
Run a vinegar or cleaner cycle to kill bacteria
Pour two cups of white vinegar into a bowl and place it on the top rack of an empty dishwasher. Run a normal hot-water cycle. The vinegar will circulate through the spray arms, dissolve mineral deposits, and kill the bacteria producing the smell. This works best if you do it once a month as maintenance.
If vinegar alone does not work, use a commercial dishwasher cleaner like Affresh or Finish. Follow the package instructions — most require you to place the product in the tub and run a hot cycle with no dishes inside. These cleaners are stronger than vinegar and break down grease and biofilm more effectively. They cost between four and eight dollars per use.
Check the drain hose for kinks and clogs
Under your sink, locate the drain hose running from the dishwasher to either the garbage disposal or the main drain. Look for kinks, pinches, or places where the hose is bent sharply — these trap water and food. Straighten any kinks gently by hand.
If the hose is kinked or clogged, disconnect it at both ends (have a bucket ready for water spillage) and run hot water through it from a faucet. If water does not flow freely, use a plumbing snake or a straightened wire coat hanger to push the clog through. Reconnect the hose and make sure it slopes downward toward the drain — never upward, which allows water to pool.
Inspect the air gap if your sink has one
An air gap is a small cylindrical device mounted on the counter or sink rim, usually near the faucet. It has a cap on top and a hose running down into the drain. The air gap prevents dirty drain water from flowing backward into the dishwasher — a problem called backflow.
If your dishwasher smells like sewage and you have an air gap, unscrew the cap and look inside. You will likely see a buildup of slime, food, or mold. Rinse the cap under hot water and use a small brush or pipe cleaner to scrub the inside of the cylinder. Flush it with hot water from a cup. Reassemble and test. If the air gap is cracked or the hose is disconnected, it needs to be replaced — a plumber can do this in under an hour for a typical service call.
Check for a clogged main drain line
If you have cleaned the filter, run a vinegar cycle, straightened the hose, and the smell persists, the problem is likely in your home's main drain line, not the dishwasher itself. This happens when hair, grease, or other debris has built up in the pipes under your sink or in the wall, blocking water from flowing out of the dishwasher.
You can test this by running water in your sink while the dishwasher is draining. If the sink water backs up or drains slowly, the clog is in the main line. You can try using a plumbing snake in the sink drain, but if that does not work, you will need a plumber to clear the line. This typically costs between one hundred and three hundred dollars depending on the severity and location of the clog.
Prevent future sewer smells with monthly maintenance
Run a vinegar cycle once a month with no dishes inside. This keeps bacteria from building up and catches small clogs before they become problems. After each load, rinse large food scraps off plates before loading them — the dishwasher filter is not designed to handle chunks of food.
Check the drain hose twice a year to make sure it has not kinked or shifted. If you have an air gap, rinse the cap every few months. These small steps take five minutes total and will keep your dishwasher smelling fresh and working longer.
Frequently Asked Questions
Can I use bleach to clean the smell out of my dishwasher?
No. Bleach can damage the rubber seals and stainless steel interior of your dishwasher. Use white vinegar or a dishwasher-specific cleaner instead. Both are safe for all dishwasher materials and work just as well.
Should I run the garbage disposal before starting the dishwasher?
Yes, if your dishwasher drains into the garbage disposal. Run the disposal for a few seconds to clear any debris. This prevents the dishwasher drain from backing up into the disposal and creating a smell.
What if the smell comes back after I clean everything?
The clog is likely deeper in your home's drain line or the dishwasher has an internal leak allowing water to sit in a hidden area. Call a plumber to inspect the drain line and, if needed, the dishwasher itself. Do not ignore the smell — standing water can damage your dishwasher over time.
Is a sewer smell from the dishwasher dangerous?
The smell itself is not toxic, but it indicates bacteria and mold are present. This is unpleasant and can affect the cleanliness of your dishes. Clean the machine promptly to stop the smell and prevent mold from spreading.