What is the minimum static pressure drop required when flow testing fire hydrants?

What is the minimum static pressure drop required when flow testing fire hydrants?
A . 5 percent
B . 10 percent
C . 15 percent
D . 20 percent

View Answer

Answer: B

Explanation:

When performing a fire hydrant flow test, a minimum static pressure drop is required to ensure that the test provides accurate and meaningful results. According to NFPA 291, Recommended Practice for Fire Flow Testing and Marking of Hydrants:

A 10 percent pressure drop is the minimum acceptable difference between the static pressure (no flow) and residual pressure (while flowing).

This drop ensures that water flow is sufficient for an accurate test and reflects the system’s capacity under actual fire conditions.

5 percent (A): Too low to provide reliable results.

15 percent (C) and 20 percent (D): Higher drops are acceptable but not the minimum requirement.

Reference: NFPA 291, Section 4.9: Static pressure drop requirements during flow testing.