Which statement correctly expresses air gap installation requirements?

Which statement correctly expresses air gap installation requirements?

• A. The air gap must be two times the diameter of the pipe, never less than one inch
• B. The air gap must be three times the diameter of the pipe, never less than two inches
• C. The air gap must be equal to the pipe diameter in inches
• D. The air gap has no minimum size

Answer: (B)

An air gap protects the potable supply by providing a physical separation large enough to prevent backflow or back-siphonage into the system. The correct requirement states the gap must be three times the diameter of the supply pipe, never less than two inches. This sizing scales with pipe size to maintain a reliable barrier, while the minimum of two inches ensures a practical clearance for small pipes. For example, a 1/2-inch pipe would need at least 1.5 inches by ratio, but the minimum makes it 2 inches; a 2-inch pipe would require a 6-inch gap. The other options either set too small a gap for larger pipes or fail to establish a minimum, which could allow backflow to occur.

An air gap protects the potable supply by providing a physical separation large enough to prevent backflow or back-siphonage into the system. The correct requirement states the gap must be three times the diameter of the supply pipe, never less than two inches. This sizing scales with pipe size to maintain a reliable barrier, while the minimum of two inches ensures a practical clearance for small pipes. For example, a 1/2-inch pipe would need at least 1.5 inches by ratio, but the minimum makes it 2 inches; a 2-inch pipe would require a 6-inch gap. The other options either set too small a gap for larger pipes or fail to establish a minimum, which could allow backflow to occur.