The National Fire Protection Association (NFPA) outlines fire hydrant testing that measures real-world pressure and flow in the water distribution system.
A hydrant flow test measures the water flow capacity at the hydrant. This test is useful to determine the flow rate available from a hydrant for a fire emergency. This test also verifies the mechanical operation of the hydrant, as well as the piping and valves serving the hydrant.
Regular fire hydrant testing ensures the ability to provide water at an acceptable pressure and flow rate for public health and firefighting operations. Most jurisdictions also require hydrant flow tests to design fire sprinkler systems for commercial or residential structures.