What type of valve is required immediately ahead of each water-supplied appliance?

The requirement for a control valve to be installed immediately ahead of each water-supplied appliance relates to the functionality and specific applications that these valves serve. A control valve allows for the regulation of water flow to the appliance, enabling adjustments for operation and maintenance purposes. By having a control valve directly before the appliance, it provides the ability to shut off water easily for repairs or service without affecting the water service to other fixtures, offering convenience and safety.

Additionally, control valves are often designed to manage not only the flow but can also facilitate temperature adjustments and pressure stabilization, which can be critical for the efficient operation of various appliances, such as dishwashers or water heaters. This makes control valves an essential component in plumbing systems that ensure both operational efficiency and user safety when dealing with water-supplied appliances.

In contrast, while shut-off valves can also serve a similar purpose of stopping the flow of water, they do not offer the same level of control and adjustments as control valves do. Pressure relief valves are mainly utilized to protect against excessive pressure buildup, and backflow prevention valves are designed to stop contamination from entering the water supply, thus having different functions that are not focused on regulating flow directly to appliances.