Which is a common size of hydrant outlet?

The most common size of hydrant outlet is 2½ inches (65 mm). This size is widely used in the fire service for a number of reasons, primarily related to the flow capacity required to effectively combat structure fires and the compatibility with firefighting equipment.

2½-inch outlets are large enough to deliver a sufficient volume of water while remaining manageable for firefighters to connect hoses and maneuver during firefighting operations. This size is a standard for many fire departments, allowing for uniformity in equipment and ease of access across different systems.

Choosing the right outlet size is crucial for operational efficiency. While other outlet sizes do exist, such as the 1½-inch outlet which is used primarily for smaller flow applications or sprinkled system connections, the 2½-inch outlet strikes a balance between sufficient flow and ease of handling, making it the most common choice for hydrant design.