What size fire department connection should be provided for a standpipe system?

• A. 1 1/2 inch
• B. 3 inch
• C. 4 inch
• D. 2 1/2 inch

Answer: (D)

The size of the fire department connection is chosen to balance compatibility with standard firefighting equipment and the ability to deliver enough water without excessive pressure loss. For most standpipe systems, a 2 1/2 inch connection is used because it matches the common discharge outlets and hose sizes that engine companies carry, allowing quick, unobstructed access to the system and sufficient flow to meet typical demand. Larger sizes (such as 3 or 4 inches) are reserved for specialized, high-flow scenarios or very large-diameter mains; they aren’t needed for standard installations and can complicate connections. A smaller size would choke the flow and hinder firefighting operations, so the standard practice is to provide a 2 1/2 inch fire department connection.