What device is used to protect traps from siphonage?

Air-admittance valves play a crucial role in plumbing systems by allowing air to enter the drainage system while preventing sewer gases from escaping into the home. When a fixture is drained, a vacuum can be created within the drain lines, which can potentially siphon water out of the traps. This loss of trap water can lead to sewer gases entering the living space, posing health hazards.

By utilizing air-admittance valves, these devices help maintain a proper air balance in the plumbing system. When a trap experiences a drop in pressure due to draining, the air-admittance valve opens to equalize the pressure and allows air to enter the system, preventing siphonage and ensuring that the trap remains filled with water. This design feature is essential for the effective functioning of drainage systems, as it helps maintain the integrity of the trap seal.

Other options, such as backflow preventers, force balance valves, and pressure regulators, serve different purposes in plumbing systems. Backflow preventers are designed to protect potable water supplies from contamination, while force balance valves are typically used in heating systems. Pressure regulators manage water pressure within plumbing fixtures, but none of these specifically address preventing siphonage in traps like air-admittance valves do.