What type of ball cock must be used for plumbing systems?

The anti-siphon type ball cock is essential for plumbing systems because it is specifically designed to prevent the backflow of contaminated water into the clean water supply. This is crucial in maintaining the integrity of potable water systems and adhering to health and safety codes. The anti-siphon mechanism works by creating a physical barrier that stops water from siphoning back into the tank when the water level drops, thus preventing potential contamination from occurring.

In general plumbing applications, it's important to prevent any situation where negative pressure could draw water backward into the supply line, especially from areas like toilets and tanks where wastewater is present. The anti-siphon design often includes features such as a vent to allow air intake that interrupts the siphoning action.

Other types, such as the standard, float, and pressure types, do not inherently include the backflow prevention features that the anti-siphon type offers. Thus, their use in systems where cross-contamination could occur does not comply with plumbing codes aimed at protecting public health.