Quick answer
To fix a dishwasher air gap cap issue, first confirm the cap is loose or clogged. Turn off the dishwasher power and water supply. Clean the cap with warm water and a brush, then reseal it. If it still leaks, replace the gasket or the entire air gap unit.
Confirm the symptom
- Water pooling around the air gap cap
- Foul odors coming from the air gap
- Dishwasher leaks near the sink or countertop
- Dishes not draining properly
- Standing water in the sink
Tools and prep
- Screwdriver (flathead or Phillips, depending on your model)
- Plumber's putty or silicone sealant
- Soft brush or toothbrush
- Warm water and mild detergent
- Rag or towel
- Turn off the dishwasher power at the circuit breaker
- Shut off the water supply to the dishwasher
Step-by-step troubleshooting
- Inspect the Air Gap CapDo: Visually check the air gap cap for cracks, looseness, or debris.Observe: Cracks or looseness may indicate a faulty seal.Means: The cap may need tightening or replacement.Next: If the cap is loose, proceed to tighten it. If it's damaged, replace it.
- Clean the Air Gap CapDo: Remove the cap and clean it with warm water and a soft brush. Rinse thoroughly.Observe: Debris or buildup inside the cap can block drainage.Means: A clogged cap can cause water to back up into the sink.Next: Reinstall the cap after cleaning. Check for leaks.
- Tighten the Air Gap CapDo: If the cap is loose, apply plumber's putty around the base and press it firmly into place.Observe: The cap should sit flush against the countertop without gaps.Means: A secure seal prevents leaks and odors.Next: Test the dishwasher to see if the issue is resolved.
- Replace the Air Gap CapDo: Remove the old cap and install a new one, ensuring it matches your model.Observe: The new cap should fit snugly and align with the drain hose.Means: A damaged cap cannot be repaired and must be replaced.Next: Reconnect the dishwasher and test for leaks.
- Check the Drain Hose ConnectionDo: Inspect the hose connected to the air gap for kinks or disconnections.Observe: A disconnected or kinked hose can cause drainage issues.Means: The hose must be properly attached for the air gap to function.Next: Reattach or replace the hose if necessary.
- Test the DishwasherDo: Run a short cycle with the dishwasher empty to check for leaks or odors.Observe: No water should leak from the air gap, and no foul smells should be present.Means: The repair was successful if the system works without issues.Next: If problems persist, consider replacing the entire air gap unit.
Common causes
| Cause | Likelihood | Difficulty | Part often needed |
|---|---|---|---|
| Loose or Damaged Cap A loose or cracked cap allows water and odors to escape. | Common | Easy | Air gap cap or gasket |
| Clogged Cap or Hose Food particles or debris block the air gap, causing water to back up. | Common | Easy | None (cleaning only) |
| Faulty Seal The gasket under the cap may degrade over time, leading to leaks. | Sometimes | Easy | Air gap gasket |
| Improper Installation The cap may not have been installed correctly during initial setup. | Rare | Medium | Air gap unit |
| Corroded or Broken Air Gap Unit Over time, the metal parts of the air gap can corrode or break. | Rare | Hard | Air gap unit |
| Incorrect Water Pressure High water pressure can force water past the air gap seal. | Rare | Hard | Pressure regulator |
Parts matching
Replace the air gap cap or gasket with parts compatible with your dishwasher model. Check the manufacturer’s website or user manual for the exact part number.
- Air gap cap (often labeled as 'air gap cover')
- Air gap gasket or seal
- Plumber's putty or silicone sealant
- Air gap unit (if full replacement is needed)
Measure the diameter of the existing cap before purchasing a replacement to ensure a proper fit.
When to call a professional
- The air gap cap continues to leak after replacement
- You notice a strong sewage odor coming from the air gap
- The dishwasher still doesn't drain properly after cleaning and tightening the cap
- You're unsure about the correct part number or installation process
- There are signs of water damage under the sink or countertop
FAQ
What is a dishwasher air gap cap?
The air gap cap is a small, round cover on the countertop near the sink that prevents water and odors from backing up into the sink from the dishwasher. It allows air to enter the drain system to maintain proper drainage.
Can I use regular sealant instead of plumber's putty?
Plumber's putty is preferred because it's flexible and won't harden, which helps maintain a good seal. Regular sealant may harden over time and crack, leading to leaks.
How often should I clean the air gap cap?
It's a good idea to clean the air gap cap every 3–6 months to prevent buildup and ensure proper function. More frequent cleaning may be needed in areas with hard water or heavy use.
Why is my air gap cap making a bubbling sound?
A bubbling sound usually indicates a clogged air gap or drain hose. Clean the cap and hose to clear any blockages and restore normal function.
Is the air gap cap required by code?
In many regions, building codes require an air gap for dishwashers to prevent backflow contamination. Check your local plumbing codes to confirm requirements.