Nozzle Pressure

What Is Nozzle Pressure?

Nozzle pressure is the pressure measured at the nozzle inlet that allows a fire nozzle to produce its intended flow and stream characteristics. Common fire-service reference values include about 50 PSI for many smooth-bore handlines and various fixed or combination fog nozzles designed for 50, 75, or 100 PSI. The correct target pressure is the rated operating pressure of the specific nozzle, not one universal value based only on nozzle type.

Why Nozzle Pressure Matters on the Fireground

Incorrect nozzle pressure ruins stream quality. Too little pressure produces a weak, sagging stream that fails to reach the fire seat, while excessive pressure causes extreme nozzle reaction that exhausts the nozzle operator and reduces stream effectiveness.

Relevant NFPA Standards

• NFPA 1960: Standard for Fire Hose Connections, Spray Nozzles, Manufacturer's Design of Fire Department Ground Ladders, Fire Hose, and Powered Rescue Tools
• NFPA 1930: Standard on Fire and Emergency Service Use of Thermal Imagers, Two-Way Portable RF Voice Communication Devices, Ground Ladders, Rescue Tools, Fire Hose, and Fire Hose Appliances

Field Procedures & Tactical Steps

1. Verify the type of nozzle attached (smooth-bore, automatic fog, or fixed-gallonage fog).
2. Calculate engine discharge pressure (EDP = Nozzle Pressure + Friction Loss + Appliance Loss ± Elevation Loss).
3. Set pump throttle to deliver correct NP (50 PSI for smooth-bore, 75/100 PSI for fog).
4. Bleed air from the line and inspect stream reach and shape before entry.
5. Adjust pump pressure if additional hose lengths are added to the stretch.

Common Context & Application

Maintained by the apparatus pump operator and monitored by interior hose teams during fire suppression operations.

Frequently Asked Questions about Nozzle Pressure