Red Seal Gasfitter — Class A Practice Exam

The component that regulates gas pressure in a residential system is the service regulator. This device is specifically designed to reduce the high pressure of gas coming from the supply line to a lower, more manageable pressure suitable for residential appliances. The service regulator ensures that the gas is delivered at a consistent and safe pressure, which is critical for the safe operation of gas appliances such as furnaces, water heaters, and stoves. In contrast, the other options serve different functions. A flow meter measures the volume of gas flowing through a system but does not control or regulate pressure. A backflow preventer is designed to stop the reverse flow of gas or liquids, protecting the supply system from contamination, but it does not regulate pressure. An expansion valve is typically used in refrigeration and air conditioning systems to control the flow of refrigerants and is not applicable to gas systems. Thus, the service regulator is the correct choice for regulating gas pressure in a residential setting.