Fire protection (NBC) — minimum spacing of external fire hydrants on water mains As per typical National Building Code practice, external fire hydrants along water mains are to be provided at minimum intervals of approximately:

Introduction / Context:
Fire-fighting infrastructure depends on ready access to hydrants with adequate pressure and flow. The spacing along roadways and around buildings ensures hose-reach coverage for fire appliances without excessive hose lengths or pressure losses.

Given Data / Assumptions:

• External (yard) hydrants serving building perimeters/streets.
• Typical NBC guidance for minimum spacing.
• Standard hose lengths and operational reach.

Concept / Approach:

Codes adopt hydrant spacing to balance coverage and cost. A commonly cited minimum interval is about 90 m, allowing overlapping coverage by adjacent hydrants and alignment with typical hose lengths on fire engines. Closer spacing may be required in high-hazard zones; wider spacing risks inadequate reach or delayed suppression.

Step-by-Step Solution:

Verification / Alternative check:

Fire safety planning handbooks and municipal standards frequently align with ~90 m spacing, subject to hazard category and local bylaws.

Why Other Options Are Wrong:

• 50–75 m are more stringent than the usual minimum baseline (sometimes used for special risks).
• 60 m is not a standard baseline figure in many NBC-derived schedules.

Common Pitfalls:

• Ignoring site obstructions that may necessitate closer spacing despite code minima.

Final Answer:

90 m.