Step-by-step fix
Step 1: Confirm the air gap assembly is the problem
- Look at the air gap on top of the sink or countertop and under the sink for cracks, a loose body, missing cap pieces, or water leaking from the assembly itself.
- Run a short drain cycle or cancel-drain cycle while watching the air gap area. A failed assembly usually leaks from the body, base, or hose connections.
- Remove the decorative cap and check for obvious debris at the top opening. If the top is just clogged, cleaning may solve the problem without replacement.
- Check the hoses under the sink. If the leak is actually coming from a split drain hose or a loose clamp, replacing the air gap will not fix it.
If it works: You have confirmed the air gap assembly is damaged, leaking at its body or seal, or too worn to reuse.
If it doesn’t: If the air gap is not damaged and the problem is only a blockage, clean the air gap and drain hose path first instead of replacing the assembly.
Stop if:- The sink deck or countertop around the air gap is cracked, badly corroded, or too damaged to hold a new assembly securely.
- The leak is coming from the dishwasher supply line, shutoff valve, or another plumbing connection unrelated to the air gap.
Step 2: Shut off power and set up the work area
- Turn off power to the dishwasher at the breaker or unplug it if the plug is accessible.
- Place towels and a small bucket under the sink below the air gap hoses.
- Take a quick photo of the hose routing before disconnecting anything. One hose runs from the dishwasher to the air gap, and the larger hose usually runs from the air gap to the sink drain or disposal.
- Remove the decorative cap from the top of the air gap so the body is easier to hold while you work underneath.
If it works: The dishwasher is safely off, the cabinet is protected, and you have a reference for hose placement.
If it doesn’t: If you cannot safely shut off power or access the air gap connections, pause and get help before continuing.
Stop if:- You find damaged wiring, standing water near electrical connections, or signs of overheating under the sink.
Step 3: Disconnect the old air gap assembly
- Under the sink, loosen the hose clamps on both air gap hoses.
- Twist each hose gently to break it free, then pull it off the air gap ports. Let any trapped water drain into the bucket.
- Loosen and remove the mounting nut that holds the air gap body to the sink or countertop.
- From above, lift the old air gap assembly out of the opening and remove any old gasket material or grime from the mounting surface.
If it works: The old air gap assembly is out and the opening is clean and ready for the new part.
If it doesn’t: If a hose is stuck, rotate it gently with pliers and work it loose without crushing the hose. If the hose tears, replace that hose before reassembly.
Stop if:- A drain hose is brittle, split, or too swollen to seal on the new air gap.
- The sink or countertop opening is damaged enough that the new air gap will not sit flat or tighten securely.
Step 4: Install the new air gap assembly
- Compare the new dishwasher air gap assembly to the old one so the inlet and outlet ports are oriented the same way.
- Set the new gasket or trim pieces in place as supplied with the replacement part.
- Insert the new air gap body through the sink or countertop opening from above.
- Thread the mounting nut on from below and tighten it until the air gap is snug and upright. Do not overtighten and risk cracking trim pieces or distorting the mounting surface.
- Reinstall the top trim or cap loosely for now if it was removed during setup.
If it works: The new air gap assembly is mounted straight, secure, and ready for the hoses.
If it doesn’t: If the body spins or sits crooked, loosen it, reseat the gasket, and tighten again until it sits flat.
Stop if:- The new part does not match the hose sizes or mounting style of the original assembly.
Step 5: Reconnect the hoses in the correct positions
- Reconnect the smaller dishwasher drain hose to the air gap inlet port and the larger outlet hose to the port leading to the sink drain or disposal.
- Push each hose fully onto its port so the connection covers the barb or fitting evenly.
- Position the clamps over the sealing area of each hose and tighten them firmly.
- Check that neither hose is kinked, pinched, or rubbing sharply against the cabinet or plumbing.
- Snap or thread the decorative cap fully into place on top of the air gap.
If it works: Both hoses are secure, routed cleanly, and attached to the correct ports.
If it doesn’t: If you are unsure which hose goes where, use your photo and trace each hose by hand before testing. The dishwasher hose and the drain-to-disposal hose should not be swapped.
Stop if:- A hose will not stay on the port, the clamp cannot tighten securely, or the hose size does not match the new air gap.
Step 6: Restore power and verify the repair during real draining
- Turn the breaker back on or plug the dishwasher back in.
- Run the dishwasher long enough to reach a drain cycle, or use a cancel-drain cycle if your machine has one.
- Watch the air gap from above and below the sink while it drains. Check the body, mounting area, and both hose connections for leaks.
- Listen for smooth draining into the sink drain or disposal without backing up at the air gap.
- Wipe the area dry and check again after a second drain cycle to make sure the repair holds under normal use.
If it works: The dishwasher drains normally and the new air gap assembly stays dry at the top, base, and hose connections.
If it doesn’t: If water still comes out of the air gap opening, the drain path to the sink drain or disposal is likely restricted and needs to be cleared. If the leak is at a hose connection, reseat the hose and clamp and test again.
Stop if:- Water leaks from a hidden connection you cannot reach safely.
- The dishwasher still backs up or overflows after the new air gap is installed, which points to a clog or drain problem elsewhere.
Replacement Parts
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FAQ
What does a dishwasher air gap do?
It helps prevent dirty sink or drain water from flowing back into the dishwasher drain line. It creates a physical break in the drain path above the sink level.
How do I know if I need to replace the air gap instead of cleaning it?
Replace it if the body is cracked, the mounting area leaks, the ports are damaged, or the assembly will not seal securely anymore. If it is only clogged with debris, cleaning is usually enough.
Why is water coming out of the top of the air gap?
That usually means the drain path after the air gap is restricted. The hose from the air gap to the sink drain or disposal may be clogged, kinked, or installed poorly.
Can I reuse the old hoses?
Usually yes, if they are still flexible, the ends are not split, and they fit the new air gap ports securely. Replace any hose that is brittle, swollen, or damaged.
Do I need sealant to install a new dishwasher air gap assembly?
Usually no. Most air gap assemblies use their own gasket and mounting hardware. Follow the replacement part's included pieces and avoid adding sealant unless the part instructions specifically call for it.