What type of valve must be installed at each building water supply line?

In plumbing systems, the requirement for a full open gate valve at each building water supply line is crucial for several reasons. A full open gate valve is designed to allow unrestricted flow of water when it is fully opened, making it ideal for use in supply lines. This type of valve provides a reliable way to isolate a section of the plumbing system for maintenance or in case of emergencies, like a leak.

Having a full open gate valve ensures that water can be quickly shut off without restricting flow, which is especially important for buildings where water supply management is critical for operation. Additionally, it meets building codes and standards that decree that each supply line should have an accessible means of control.

The other types of valves have different functions. Check valves are used to prevent backflow, while ball valves are useful for throttling flow but don't always provide the same level of isolation as a gate valve when fully opened. Pressure relief valves are specifically designed to release excess pressure to protect the plumbing system but don't serve the purpose of controlling the water supply line directly. Thus, the full open gate valve is the appropriate choice for this specific requirement.