Nozzle Reaction

Smoothbore Nozzle Reaction

Estimate the pushback force created by a smoothbore stream.

What It Tells You

The approximate reaction force firefighters must control.

Formula

NR = 1.57 × d² × NP

What the Variables Mean

NR
nozzle reaction pounds
d
tip diameter inches
NP
nozzle pressure PSI

Plain-Language Explanation

Water leaving the tip pushes back on the nozzle. A larger tip or higher pressure increases that force.

Worked Example

Use a ⅞-inch tip at 50 PSI.

  1. NR = 1.57 × 0.875² × 50
NR ≈ 60 lb

Fireground Takeaway

A stream can be hydraulically correct and still be difficult to handle. Reaction matters to crew control and placement.

Practice This Formula

Open Reverse Flow and start a Practice Quiz filtered to this topic.

Browse more formulas