Symptoms
- Water bubbles up and overflows from the small cap near the faucet
- Happens during or after the dishwasher's drain cycle
- Dishwasher may also seem to drain poorly or not at all
- Countertop around the air gap gets wet
Likely causes
- CommonClogged dishwasher drain hoseFood debris or a kink can restrict how fast water leaves the dishwasher.
- CommonClogged garbage disposal or its dishwasher inletIf the dishwasher drains through the disposal, a clog there backs up into the air gap.
- PossibleDebris built up inside the air gap fitting itselfFood particles can accumulate in the small chamber over time.
- PossibleKnockout plug not removed on a newly installed disposalA common oversight that fully blocks the dishwasher connection.
What to do
- Twist off and remove the air gap cap and clean out any visible debris inside.
- Check the dishwasher's drain hose under the sink for kinks and straighten if needed.
- If the dishwasher drains through a garbage disposal, run the disposal briefly to clear any debris, or check that the knockout plug was removed if the disposal is new.
- Disconnect the dishwasher drain hose at the disposal or drain connection and check for clogs, clearing any debris found.
- Reconnect everything securely and run the dishwasher's drain cycle to confirm water flows without backing up into the air gap.
- If the air gap continues to overflow, check further along the drain line for a deeper clog.
Tools and parts
- Screwdriver
- Pliers
When to call a pro
Call an appliance repair tech or plumber if clearing the hose and disposal connection doesn't stop the overflow.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.