For pipe sizes 2 1/2 in. and larger, the minimum bend radius is which of the following?

For pipe sizes 2 1/2 in. and larger, the minimum bend radius is which of the following?

• A. Three pipe diameters
• B. Seven pipe diameters
• C. Ten pipe diameters
• D. Five pipe diameters

Answer: (D)

Bend radii tell you how gently the pipe is curved, and in standpipe systems that gentleness matters for both flow and durability. For pipes sized 2 1/2 in and larger, the standard requires a minimum bend radius of five times the pipe diameter. This keeps bends from getting too tight, which would risk kinking, placing excessive stress on fittings, and reducing the internal flow area, all of which can raise friction losses and limit discharge during a fire. Using three times the diameter would be too sharp for larger pipes, increasing the chance of damage and flow issues; seven or ten times the diameter would be unnecessarily large without added benefit in most layouts. Five times the diameter strikes a practical balance between safe, reliable flow and reasonable installation space.

Bend radii tell you how gently the pipe is curved, and in standpipe systems that gentleness matters for both flow and durability. For pipes sized 2 1/2 in and larger, the standard requires a minimum bend radius of five times the pipe diameter. This keeps bends from getting too tight, which would risk kinking, placing excessive stress on fittings, and reducing the internal flow area, all of which can raise friction losses and limit discharge during a fire. Using three times the diameter would be too sharp for larger pipes, increasing the chance of damage and flow issues; seven or ten times the diameter would be unnecessarily large without added benefit in most layouts. Five times the diameter strikes a practical balance between safe, reliable flow and reasonable installation space.