When using a 1.

When the residual pressure at a 1.5 in. hose connection exceeds 100 psi, an approved pressure-regulating device is typically required to ensure user safety and to prevent damage to equipment connected to the hose outlet. This helps maintain manageable hose stream pressures for firefighting operations.

References: NFPA standards for the installation and use of hose connections in sprinkler systems, focusing on safety and operational effectiveness.