What is the valve called that is placed in front of a Hydrant?

The valve that is placed in front of a hydrant is commonly known as the auxiliary valve. This valve serves an essential purpose in water distribution systems, allowing for the control of water flow to the hydrant itself. It enables operators to isolate the hydrant for maintenance or repairs without affecting the rest of the system or the hydrant's functionality.

In the context of water utility operations, knowing the correct naming and function of various valves is crucial. While the main valve is generally used to control the flow of water within a larger section of the pipeline system, and check valves are designed to prevent backflow, neither of these would be specifically designated for controlling access to a hydrant. Moreover, relief valves are typically used to relieve excess pressure in a system rather than control flow directly to specific devices like hydrants. Thus, the auxiliary valve is the appropriate designation for this specific installation.