During a fire flow test, which hydrant is used to read static and residual pressures?

• A. Test hydrant
• B. Fire hydrant
• C. Service hydrant
• D. Relief hydrant

Answer: (A)

In a fire flow test, you need to measure two pressures at the same point in the distribution system: the static pressure when no water is flowing, and the residual pressure while water is being drawn at the test flow. The hydrant chosen for this measurement is the designated test hydrant. It is set up specifically for the test, isolated from normal firefighting and service use, and equipped with gauges to read both pressures accurately. Using this hydrant ensures the readings reflect the actual system pressure at that point without interference from other flows.

Other hydrants aren’t appropriate for these readings because active firefighting hydrants or service hydrants can alter the pressure in the area being tested and won’t provide a controlled, repeatable measurement point. The test hydrant provides a stable, known location and setup for obtaining reliable static and residual pressures.