Quick Answer:
A brief burst of odor right when the dishwasher drains often comes from the dishwasher discharge mixing with the sink branch or garbage disposal. Check that the drain hose has a proper high loop or air gap, run the dishwasher and sniff at the moment it drains to locate the source, and then run the sink faucet for about 30 seconds after the drain cycle to push the discharge past the sink trap.
Why This Happens
Dishwashers drain into the sink plumbing or a garbage disposal. If wastewater sits in the sink branch or disposal, smells can back up into the sink area when the dishwasher pushes its discharge through the line. A missing or low drain hose loop or a blocked sink trap makes it easier for those odors to escape. Other causes include food trapped in the disposal, a partially dry P-trap, or buildup inside the drain line.
If other recent events might explain odors, you may also want to check related issues like Food odor after city outage where spoiled food or standing water plays a role.
Step-by-Step What to Do
1. Confirm the dishwasher drain hose has a high loop or air gap
- Open the cabinet under the sink and look at the dishwasher drain hose. It should rise up and be secured to the underside of the countertop (a “high loop”) or connect to a visible air gap device on the sink before dropping to the disposal or drain.
- If the hose drops straight down from the dishwasher to the disposal, that low route can let sink odors travel back toward the dishwasher and sink.
2. Run the dishwasher and sniff at the moment it drains
- Run a normal cycle with the sink cabinet open so you can hear and smell the drain moment. The odor’s timing tells you whether it’s coming from the dishwasher hose, the disposal, or the sink trap.
- Stand near the sink and sniff around the drain and cabinet opening as the final drain happens. If the smell is strongest at the disposal or sink drain, the problem is in the sink branch; if it smells at the hose connection, the hose or air gap may be the issue.
3. Run the sink faucet for 30 seconds after the drain cycle
- As soon as the dishwasher finishes draining, run the kitchen sink faucet (hot or warm) for about 30 seconds. That flushes the dishwasher discharge past the sink branch and down the trap, reducing the chance of a short burst of odor.
- If you have a garbage disposal, run it briefly while the faucet is on to help clear solids.
4. Clean the disposal and trap if odors persist
- If the smell continues, clean food buildup from the disposal and run hot water down the drain to flush the trap. Use gloves and avoid mixing drain chemicals.
- For persistent buildup deeper in the line, a mechanical snake or a plumber may be needed.
What Not to Do
- Don’t remove the dishwasher high loop or lower the hose to “help it drain.” Lowering that hose removes the barrier that prevents sink odors from backing up and can make smells worse.
- Don’t pour strong chemicals into the disposal or drain without knowing the plumbing layout—mixing chemicals or using large amounts can be dangerous and may damage pipes.
- If dishwasher draining repeatedly stinks up the sink despite these checks, a plumber is appropriate—don’t keep trying risky fixes yourself.
When to Call a Professional
- Persistent sewer-like smells after flushing and cleaning.
- Repeated backing up, gurgling sounds, slow drains, or any leak you cannot fix.
- If you suspect a deeper trap problem or damaged plumbing. If your house was recently winterized or thawed and sinks now smell, see guidance like Sink smells after winterization or call a pro to inspect.
Safety Notes
- Turn off power at the breaker before working inside the disposal cabinet or touching electrical components.
- Wear gloves and eye protection when cleaning garbage disposals or traps. Be careful with sharp objects.
- Avoid mixing household chemicals. If you use drain cleaners, follow the label instructions and do not mix different types.
- Ventilate the area while sniffing for odors—do not inhale concentrated fumes.
Common Homeowner Questions
- Why does the smell only appear during the drain cycle? — The dishwasher pushes a slug of wastewater through the sink branch; it can stir up trapped odors that escape briefly at that moment.
- Will running the sink after each cycle permanently fix it? — Running the sink flushes the immediate discharge and often stops the short burst of odor, but it won’t fix underlying buildup or plumbing issues.
- Can I relocate a dishwasher hose myself to add a high loop? — You can reposition and secure the hose under the countertop if it’s accessible, but if routing is unclear or fittings are tight, a plumber is safer.