What must be installed to protect the water supply when a dishwasher is used?

When a dishwasher is used, it is essential to protect the water supply from contamination, and the installation of an air gap or a device that prevents backflow serves this critical function. An air gap creates a physical separation between the water supply and the dishwasher's drain, ensuring that wastewater cannot siphon back into the potable water system. This is particularly important because dishwashers can discharge wastewater that may contain food particles, detergents, and other contaminants.

A device that prevents backflow, like a backflow preventer, also meets this requirement by allowing water to flow in one direction only, thus preventing any reverse flow of contaminated water back into the clean water supply. Therefore, having either an air gap or a backflow prevention device is mandated by plumbing codes to ensure safe and non-contaminated drinking water.

Other options, while they may serve important functions in plumbing systems, do not specifically address the protection of the water supply in the context of dishwasher usage. For example, a check valve primarily prevents backflow in systems where water needs to flow in one direction, but it does not provide the same effective protection against contamination as an air gap or approved backflow prevention device. A filtration system serves to clean water but does not address the issue of direct