Symptoms
- Water sprays or bubbles out of the small cap next to the faucet
- Happens during or right after the dishwasher runs
- Dishwasher also seems to be draining slowly or not at all
- No leak when the dishwasher isn't running
Likely causes
- CommonClogged dishwasher drain hose or garbage disposal knockout plugIf drain water can't flow out fast enough, it backs up and out through the air gap by design, to protect against contamination.
- CommonKinked dishwasher drain hoseA pinched hose under the sink restricts drainage.
- PossibleClogged garbage disposal drain nippleOn a new disposal, the internal knockout plug for the dishwasher connection may not have been removed.
- PossibleDebris clogged inside the air gap itselfFood particles can build up inside the air gap cap over time.
What to do
- Remove the air gap cap and clean out any visible debris inside it.
- Check the dishwasher drain hose under the sink for kinks and straighten it if needed.
- If the garbage disposal was recently installed or replaced, confirm the knockout plug for the dishwasher connection was removed.
- Run the dishwasher's drain cycle and watch the air gap and the disposal or drain connection to see where water is backing up.
- Clear any clog found in the disposal's dishwasher inlet or the drain hose.
- Run the dishwasher again and confirm the air gap stays dry during the drain cycle.
Tools and parts
- Pliers
- Screwdriver
When to call a pro
Call an appliance repair tech or plumber if clearing the hose and disposal connection doesn't stop the air gap from overflowing.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.