Quick Answer:
Suds rising into the sink during a dishwasher cycle usually come from too much or the wrong type of detergent, or from a partial drain obstruction that lets suds back up. Pause the dishwasher, pour plain water down the sink to clear the trap, and confirm you’re using the correct amount and type of detergent before running the cycle again.
Why This Happens
Dishwashers and kitchen sinks share a drain path. If the dishwasher releases soapy water and the drain is slow or blocked, foam can be pushed into the sink instead of flowing away. Common causes:
- Using regular dish soap (not dishwasher detergent) or using too much powder/liquid detergent.
- Partially clogged drain lines, a full sink trap, or a recently changed disposal that wasn’t reconnected correctly.
- A dishwasher drain hose that’s kinked or not looped high enough to prevent backflow.
If you recently changed the garbage disposal, check the advice on Backup after replacing disposal. If the issue happens only during the dishwasher’s drain phase, see Backup only when dishwasher drains for related checks.
Step-by-Step What to Do
1. Pause the cycle and stop more suds
- Open the dishwasher and press the pause or cancel button to stop the current cycle. If the machine won’t pause, turn off its power at the control or the appliance breaker.
- Keep the dishwasher door slightly open to avoid pressure pushing more suds out into the sink.
2. Flush the sink trap with plain water
- Remove standing foam from the sink with a cup or small container.
- Boil or heat fresh water (not chemicals) and slowly pour a few liters down the sink to push suds and soapy water through the P-trap and into the drain line.
- If the sink still drains slowly after flushing, the trap may need to be removed and cleaned. Turn off the water and place a bucket under the trap before loosening it.
3. Confirm detergent type and amount
- Check the detergent label: dishwasher machines need low-sudsing dishwasher detergent, not hand dish soap.
- Measure carefully — follow the manufacturer’s dosing guidance for your water hardness and load size. Using more than recommended increases suds and the chance of backup.
4. Clear and inspect drain connections
- Check the dishwasher drain hose for kinks, sharp bends, or a missing high loop/air gap that prevents backflow.
- If you have a garbage disposal, ensure its knockout plug was removed when the disposal was installed and that connections are tight.
5. Run a rinse-only test
- After flushing and checking detergent, run a short rinse cycle with the dishwasher empty and no detergent. Watch the sink for any renewed foaming or backup.
- If the problem is gone, resume normal use with correct detergent and amounts.
What Not to Do
- Do not add extra detergent to test cleaning; excess suds can worsen backup behavior.
- Do not mix different drain-cleaning chemicals or pour caustic drain cleaners into the dishwasher or connected sink without professional advice—these can be hazardous and may damage plumbing or the dishwasher.
- Do not reach into the disposal or drain while the appliance or disposal is powered. Always disconnect power first.
When to Call a Professional
- Call a plumber if flushing the trap and checking the hose don’t stop the backup, or if the sink drains very slowly after clearing suds.
- Contact a technician if you suspect a disposal installation issue, a more serious clog deep in the building drain, or if you find leaks when inspecting connections.
- If the dishwasher repeatedly produces excess suds despite correct detergent and a clear drain, a service visit can check internal drain valves and pump function.
Safety Notes
- Turn off power at the breaker before working on the dishwasher or disposal electrical connections.
- Use gloves and eye protection when handling soapy water and when removing a trap; wastewater may contain food and debris.
- Avoid chemical drain cleaners with dishwashers and disposals; they can harm seals and create dangerous fumes if mixed with other cleaners.
Common Homeowner Questions
- Why did suds start appearing suddenly? A recent change in detergent type/amount or a developing clog is usually the cause.
- Can I just run more cycles to clear the suds? No. Running more cycles with suds can push more foam into the sink or dishwasher; pause and flush first.
- Is this likely to damage the dishwasher? Occasional suds won’t usually harm the machine, but repeated backups or water in the bottom of the dishwasher should be checked to avoid motor or pump damage.