What must be installed in equipment with a direct connection to the potable water supply?

In equipment that has a direct connection to the potable water supply, atmosphere vacuum breakers must be installed to prevent backflow. Backflow can occur when there's a drop in water pressure, which might allow potentially contaminated water to flow back into the clean water supply.

Atmosphere vacuum breakers create a physical barrier that prevents this backflow by allowing air to enter the system when there is a negative pressure, thus preventing any contaminate from siphoning back into the potable water line. This is crucial in safeguarding public health and ensuring that the drinking water remains uncontaminated.

Other options may serve important functions in plumbing systems, but they do not specifically address the need for preventing backflow in connection to potsable water supplies. For instance, while water filters can improve water quality by removing certain impurities, they do not protect against backflow. Pressure regulators control water pressure but do not prevent contamination. Air valves can serve a purpose in some systems but lack the specific function needed in this context.