The waistline of an automatic clothes washer shall discharge through a(n) _____.

The discharge from the waistline of an automatic clothes washer should go through an air break. An air break is a method designed to prevent backflow of wastewater into the clean water supply, ensuring that there is a physical separation between the outlet of the washer and the drainage system. This is crucial for maintaining sanitary conditions and preventing contamination.

In this scenario, the air break works by allowing air to enter the system, which effectively prevents siphoning and thus reduces the risk of wastewater from the drainage system being drawn back into the clothes washer. This is particularly important since washers discharge water that may contain detergents and other contaminants.

While backflow preventers and vacuum breakers are also devices intended to prevent backflow, they are typically used in different contexts or applications. Backflow preventers are often applied in more complex plumbing scenarios and are installed at the point of service, while vacuum breakers are usually used in situations involving hoses or valves to protect potable water from backflow.

In summary, the air break specifically provides an effective means of discharging the waistline from a clothes washer while ensuring safe and sanitary wastewater management.