What That Chrome Cylinder on Your Countertop Actually Does
That 2-inch cylindrical fitting mounted into your kitchen sink deck is a physical backflow prevention air gap. Inside that chrome decorative hood is a dual-chambered plastic valve:
- A smaller 5/8-inch inlet hose brings pressurized dirty water up from the dishwasher pump.
- The water arcs over an open air gap and falls by gravity into a larger 7/8-inch hose connecting down to your garbage disposal or sink drain tailpiece.
Because there is a literal pocket of ambient air separating the two water streams, it is physically impossible for dirty sink water to ever siphon back into your dishwasher tub, even if the city sewer backs up.
Why Water Geysers Out of the Holes
When clean water sprays out the air gap slots onto your counter, your dishwasher pump is doing its job perfectly. The failure is completely on the downstream side:
The larger 7/8-inch rubber hose between the air gap and your garbage disposal has become choked with a plug of solidified cooking grease, dried pasta, or fibrous vegetable pulp. When the dishwasher pump pushes 20 gallons per minute up into the air gap, the water hits the grease obstruction in the larger hose, cannot fall into the disposal, and erupts out of the air relief holes onto your kitchen counter.
How to Clear the Air Gap in 5 Minutes (Without a Plumber)
You can usually clear this without tools:
- 1. Pull Off the Decorative Chrome Hood: Grab the metal cylinder and pull straight up. It simply friction-fits over the plastic inner housing.
- 2. Remove the Plastic Cap: Modern air gaps have a plastic diverter cap held by two snap clips. Squeeze the tabs and pop off the inner cap.
- 3. Clear the Upper Yoke: You will likely see a clump of hair, coffee grounds, and grease lodged in the top diverter channel. Pluck it out with needle-nose pliers or a cotton swab.
- 4. Clear the Downstream Hose: Place an empty paper towel tube over the larger 7/8-inch hole and blow firmly through it, or slide a flexible bottle brush down the line into the disposal. You will hear a distinctive "thump" as the grease plug dislodges into the disposal chamber.
- 5. Run the Disposal: Turn on your cold kitchen faucet and run the garbage disposal for 15 seconds to grind away the dislodged debris.
When to Call West Coast Wrench
If clearing the upper air gap does not stop the water overflow, you may have a sagging, kinked discharge hose under the sink, a crushed barb fitting on the garburator, or a dishwasher check valve failure causing excessive surging pressure. Our technicians service kitchen drainage and dishwashers across Greater Victoria.