What is the best way to prevent backflow?

The best way to prevent backflow is through the use of an air gap. An air gap creates a physical separation between the source of contamination and the potable water supply. This separation is achieved by ensuring that there is an unobstructed vertical space between the highest point of the water supply and the potential source of contamination, such as a sink or other fixture.

An air gap is highly effective because it relies on gravity, which cannot be overcome by pressure changes in the water system, ensuring that contaminated water cannot flow back into the clean water supply. This method is particularly reliable and widely used in various applications, such as in residential plumbing systems for sinks and dishwashers.

Other options like check valves, pressure relief valves, and backflow preventers also serve important roles in preventing backflow but may not be as foolproof as an air gap. Check valves can provide some level of protection by preventing reverse flow when functioning properly, but they can fail due to wear, debris, or corrosion. Pressure relief valves are designed to protect a system from excessive pressure, and while they can assist in certain backflow scenarios, they do not provide the direct prevention that an air gap does. Backflow preventers are specifically intended to prevent backflow from specific sources