Final answer:
To prevent back-flow in a sink, a check valve or an air gap can be used. A check valve allows fluid to flow in one direction and prevents reverse flow. Air admittance valves or vent pipes help maintain proper water flow and prevent vacuum conditions.
Step-by-step explanation:
To prevent back-flow in a sink, the appropriate device would be a check valve. A check valve is a type of valve that allows fluids to flow in one direction but closes to prevent flow in the reverse direction. This is crucial for maintaining sanitary conditions, as it prevents contaminated water from flowing back into the clean water supply. An air gap is also a common method used, which is a physical separation between the end of a water supply outlet and the flood level of a fixture, ensuring no backflow into the potable water system. On the other hand, a pressure regulator is used to reduce the input pressure in a plumbing system to a safe level that the system can withstand.
Within a plumbing system, air-filled tubes, often referred to as air admittance valves or vent pipes, are included to help maintain the proper flow of water. These air-filled tubes prevent vacuum conditions that can slow down water flow and allow for the release of sewer gases to the outside. They are an essential part of maintaining the health and efficiency of the plumbing system.