Evolution 3 — Dual Handlines from Hydrant

Overview

The first multi-line evolution. Operators supply two attack lines simultaneously from a single hydrant source. This introduces the challenge that defines real-world pump operations: when one line opens or closes, every other line is affected. The pump is a shared resource — increasing flow on one discharge changes the pressure on all others. Flow management and throttle discipline become critical. Most fireground pump failures happen during multi-line operations because operators do not anticipate the pressure interaction between lines. This evolution builds that anticipation through repetition.

Training Objective

Supply two attack lines with different hose sizes and flow requirements from a single hydrant. Maintain correct nozzle pressure on both lines simultaneously. When the second line opens, the operator must compensate for the pressure drop on the first line without overshooting either.

Skills Practiced

• Multi-line pressure balancing and interaction awareness
• Independent PDP calculation per line with different hose sizes
• Throttle management under changing demand conditions
• Flow demand awareness — knowing total GPM vs supply capacity
• Sequential valve opening technique to minimise pressure transients
• Anticipating pressure changes before they happen
• Reading multiple discharge gauges simultaneously

Setup

Hydrant supply with two discharge lines: a 1¾" attack line (200 ft, 150 GPM) and a 2½" backup line (200 ft, 250 GPM). Different hose sizes mean different friction loss values and different target pressures. The operator must calculate PDP for each line independently and manage the throttle to satisfy both demands from a single pump.

Scenario

A working structure fire requiring both an interior attack line and a backup/exposure line. The interior crew is flowing on the first floor while a second crew stretches a backup line to protect the exposure. The operator must keep both lines at target pressure as crews open and close nozzles. When the backup crew opens their line, the attack line pressure will drop — the operator must be ready.

What to Expect

Opening the second line will cause the first line's pressure to drop by 15-30 PSI depending on flow demand. The operator must anticipate this and adjust the throttle before the interior crew notices a pressure change. The simulation scores pressure accuracy on both lines independently and penalises large pressure swings (more than ±10 PSI from target for more than 5 seconds). Intake pressure will also drop as total demand increases.

Tips

• Calculate PDP for each line before opening any valves — know your numbers cold
• Open the higher-flow line first to establish baseline throttle position
• Make small throttle adjustments of 3-5% — large moves cause pressure spikes on both lines
• Monitor total flow demand against your supply capacity — two lines at full flow may approach your hydrant limit
• When the second line opens, increase throttle immediately — do not wait for the pressure to stabilise on its own
• Keep one eye on intake at all times — multi-line operations stress the supply