Standard pumper-connection fire hydrants should not be installed on water mains smaller than ______ inches in diameter.

Standard pumper-connection fire hydrants are designed to provide adequate flow and pressure for firefighting purposes. The critical factor in their installation is the diameter of the water main to which they are connected.

A minimum diameter of 6 inches is recommended for water mains to ensure that there is sufficient water flow and pressure available when the hydrant is activated. Larger mains support greater water volumes and can handle the surge of water required during fire emergency situations without causing significant drops in pressure. If hydrants are installed on smaller mains, such as those that are 4 inches in diameter, the flow may be insufficient, leading to inadequate firefighting capacity.

The 6-inch minimum diameter standard is typically established based on fire flow requirements outlined in fire codes and standards across the United States, ensuring that the system can deliver enough water to aid firefighting efforts effectively. This standard helps ensure that fire hydrants operate efficiently and reliably during critical emergencies.