Step 4 · Check and Clean the Drain Hose
If the top of the air gap is clean, the clog is likely in the drain hose leading from the air gap to the garbage disposal. Under the sink, locate the larger of the two hoses connected to the bottom of the air gap. Place a bucket underneath it. Loosen the hose clamp holding it to the garbage disposal inlet or sink drain tee and pull the hose off. Check the hose and the inlet port for blockages. Use a small brush or a blunt object like a screwdriver to clear any gunk. Reconnect the hose and tighten the clamp.