This device prevents the unwanted backflow of contaminated water from a washing machine’s drain hose back into the clean water supply. It functions as a one-way valve, allowing wastewater to exit but blocking any potential reverse flow. A common example is an air gap, a small vertical pipe installed above the highest possible water level of the washing machine’s standpipe or laundry tub. Alternative designs might involve integrated check valves within the drain hose connection.
Preventing backflow safeguards public health by eliminating the risk of cross-contamination between wastewater and potable water sources. Historically, the absence of such protective measures led to instances of contaminated water entering the drinking water supply, posing significant health hazards. These devices are now mandated by most plumbing codes to ensure the safety and integrity of domestic water systems.
