If you have a home inspection conducted, chances are good that you will be informed about a problem with the home’s dishwasher air gap. Installers can’t seem to get the installation right and the area is often out-of-sight … out-of-mind. A good home inspector will be able to identify the problem and call for correction.

Most dishwashers do not have built-in backflow prevention on the drain hose side. This is where the drain air gap device functions; to prevent contamination of the inside of the dishwasher. This type of contamination would occur if there was a kitchen sink drain backup. The Uniform Plumbing Code requires that an air gap device be installed at the countertop level to prevent backflow into the dishwasher. This device prevents backflow by keeping the connection above the fixture flood level rim and having an opening to atmosphere (preventing a siphon affect). The device looks like a small chrome canister usually just to the right of the sink basin. The air gap device has a vertical slot that should be directed to face the sink. At times the air gap device will fail causing discharge water to exit through the slot in the air gap device. In this case the air gap device will need to be replaced by a qualified plumber.

Some building codes allow the high loop method (fasten drain hose high at underside of countertop). This installation will work in most cases, unless a siphon occurs. Attending to the need for an air gap at the dishwasher can prevent a rather disgusting and unsanitary event should a backup occur.