Large Diameter Hose is designed to move big volumes of water over distance. It’s used in water supply operations, especially in relay setups and long lays, because the larger diameter allows more flow with less friction loss, making it possible to push water from the source to the fire scene efficiently. This makes it ideal for supplying pumpers and handling long runs. It isn’t used for interior attack work, like attic fires, where smaller, more portable handlines are preferred for maneuverability and rapid application. LDH is typically a larger-diameter supply hose (commonly in the 3–6 inch range) used specifically for delivering high water volumes rather than for direct fire attack.

When you’re deciding whether to raise nozzle pressure, watch how the fire responds to the water you’re delivering. If you’re not getting enough extinguishing effect and flames keep growing even though you’re already applying water, that’s a sign the current pressure isn’t enough to penetrate and cool the fuel and heat enough to stop the fire. Increasing nozzle pressure boosts the water’s velocity and reach, improves penetration into the flames, and enhances cooling by producing more steam and a stronger, more effective knockdown. This helps push back the heat and deny the fire the energy it needs to continue burning. The other scenarios don’t directly indicate the need to increase nozzle pressure. A drop in engine RPM typically lowers pump discharge pressure, which could reduce the effectiveness rather than signal the correct response. A constant water flow doesn’t tell you how well that flow is doing its job at the nozzle—you assess performance rather than flow rate alone. A nozzle spraying a fine mist can mean a fog pattern or low pressure, but it isn’t in itself a reliable indicator that you should increase pressure; it could be a chosen fog setting or another condition.

Accessing the intake is where you check the suction screen or basket for debris. The intake port is the point where the pump connects to the water source, and it has a screen to keep rocks, leaves, and other debris from entering the pump. When you inspect this screen, you remove the screen or access the basket to look for obstructions and clean out any rocks or debris, ensuring the pump can prime and draw water smoothly. The other ports are for delivering water (master stream, booster line, or preconnect) and aren’t used to inspect or service the suction screen.

The main idea is to confirm what the nozzle is actually seeing by measuring it, not guessing from someone’s word. To verify the correct nozzle pressure, use the nozzle’s own gauge or display and compare it to the pump’s discharge gauge after accounting for friction losses along the hose run (and any elevation changes). In other words, nozzle pressure equals the pump discharge pressure minus the friction losses along the line. This direct measurement tells you the true pressure at the nozzle, which is what affects stream shape and reach. Relying on the pump operator’s word isn’t reliable, and measuring water temperature or color doesn’t tell you about pressure.