A mechanism preventing contaminated water from being drawn back into the potable water supply is crucial for washing machines. This device often involves an air gap or a non-return valve situated in the drain hose, ensuring a break in the continuous flow of water between the appliance and the drainage system. A typical example involves a raised loop in the drain hose, positioned higher than the highest possible water level in the washing machine.
This protective measure safeguards public health by preventing backflow, particularly when negative pressure develops in the drainage system. Such situations can occur during drain blockages or municipal pumping activities. Historically, concerns regarding potential cross-contamination between wastewater and clean water supplies led to the development of these safety features. Their implementation has drastically reduced the risk of waterborne illnesses associated with washing machine usage.
