Identify a true statement about hydrant grid systems with large supply mains and looping secondary mains.

• A. Higher friction loss
• B. Less friction loss and deterioration
• C. No impact on performance
• D. Increased maintenance requirements

Answer: (B)

In a hydrant grid with large supply mains and looping secondary mains, the network is designed to carry fire flows through multiple broad paths. Larger supply mains reduce velocity for a given discharge, which lowers friction losses along those main routes. The looping secondary mains provide several parallel paths to reach hydrants, so when multiple hydrants are in use, the flow splits and each path carries less water at a lower velocity. That combination reduces overall friction losses and tends to stabilize pressure throughout the system.

Looping also minimizes stagnation by avoiding long dead-end runs, which helps keep water fresher and reduces wear and deterioration that can come from high-velocity surges and poor water quality. So, this setup tends to produce less friction loss and less deterioration compared with non-looped, smaller-diameter networks.