Dishwashers require a way to channel clean water and drain dirty water.
The dishwasher air vent is a component that is installed between the dishwasher drain hose and the sink or garbage disposal drain. These components can be mounted to a replacement sink receptacle or through a drilled hole in a countertop. There are a few different functions that a dishwasher air gap can perform, all related to how the dishwasher drains. One purpose an air gap can serve is to prevent water from running down a sink drain and accidentally drawing water from a dishwasher. The other purpose is to prevent wastewater from reaching a fresh water supply through a dishwasher, which is why some local jurisdictions have building codes that require the installation of dishwasher vents.
Dishwashers require a source of fresh water and a method of draining dirty water to work properly. They are normally connected to a fresh water supply for clean water and usually drain into the same pipe as the kitchen sink. Most garbage disposals also include a port that a dishwasher drain hose can be attached to. When a wash cycle is complete, most dishwashers have a pump that is used to direct all of the dirty water into the sink drainpipe or the trash.
In some cases, the dishwasher drain hose does not connect directly to a drain or disposal tube. Installations like these include an additional component known as a dishwasher air gap. These air gaps are usually just tubes that have protective or decorative hems covering them and a Y-connection at the bottom. One side of the Y-connection is hooked up to a dishwasher drain hose, while the other is connected to a drain or sink.
The main reason for using a dishwasher vent is to prevent siphoning, either to the outside or inside of the dishwasher. Without an air vent in the dishwasher, the dishwasher drain hose can act like a siphon under certain circumstances. Running water down the kitchen drain can accidentally drain water from the dishwasher, preventing it from working properly. There is also the possibility of sewage entering the dishwasher if it goes through a siphon and into the sink drain. If this were to happen, the wastewater could flow into the water intake and contaminate a community’s entire freshwater supply.
