How Does a Dishwasher Vacuum Breaker Work?

Positioning

• The vacuum breaker sits on the waste water drain line that runs from the dishwasher. It's typically shaped like a cylinder and made of metal with a chrome exterior. The vacuum breaker attaches to the underside of the kitchen sink, on the countertop next to the sink or elsewhere on the drain line. Some newer dishwashers have a built-in vacuum breaker that sits on the dishwasher’s connection to the drain line, instead of on the drain line itself.

Purpose

• The dishwasher’s drain line connects to the drain system on the kitchen sink, either to a drainpipe section or the waste disposal. The vacuum breaker’s valve opens whenever a vacuum begins to form in the drain line, which could result in back siphoning or back flow of waste water. When the vacuum breaker’s valve opens, the waste water in the dishwasher’s drain line flows out of the line through the vacuum breaker.

Back Flow Risks

• If the dishwasher’s drain line does not have a vacuum breaker or if the vacuum breaker is not working properly, the waste water can flow from the sink’s drainpipes or disposal and into the dishwasher. Back flow occurs when the water pressure inside the dishwasher’s drain line suddenly drops, creating a vacuum in the drain line. Food debris, bacteria and dirty water that washes down the sink’s drain or is in the drainpipes can then enter the dishwasher.

Malfunctioning Vacuum Breaker

• If your vacuum breaker is leaking water constantly, and you have just installed a new sink disposal, the problem may be with the disposal. The connection where the disposal attaches to the dishwasher’s drain line has a plug you must remove first. The hose that connects the vacuum breaker to the drainpipes or disposal may become clogged with debris, which you can remove by loosening the hose’s connections. If the vacuum breaker still leaks water constantly, it probably needs to be replaced.