Firefighting Concepts and Techniques

Red Line

• The Red Line is reached when friction loss is approximately 36 psi/100 feet of hose, indicating the need for either a larger line or additional pump to deliver the desired gallons per minute (GPM).
• Reaching the Red Line triggers decisions about adding another line or increasing the line size, based on the desired GPM and friction loss of approximately 36 psi/100 feet of hose.

Residual Pressure

• Residual pressure is the portion of total pressure not used to overcome friction or gravity while delivering water through hoses, pipes, fittings, and adapters.
• Maintaining sufficient residual pressure is crucial for safe operation; it prevents injury and damage to equipment.

Tandem Pumping

• Tandem pumping involves connecting two pumpers in series to a fire hydrant.
• One pumper directly connects to the hydrant, and the second pumper uses the excess flow from the first pumper's intake as its water source.

Vacuum Primers

• Vacuum primers utilize the existing vacuum in a gasoline engine's intake manifold.

Incrustation

• Incrustation can be caused by tubercular corrosion, rust, water's chemical constituents, or the growth of biological organisms.

Pressure Governor

• Pressure governors regulate engine power output (RPM) to maintain a set pump discharge pressure.
• If excess pressure builds up, a tube connected to the pump discharge transmits the pressure increase to a governing device, reducing the throttle.

Bleeders

• Bleeders, located on gated intakes (5" intake relief valve), release air as a supply line is being filled before opening the gated intake.

Flowmeters

• Four basic types of flowmeters: Differential, Turbine, Paddlewheel, and Spring Probe.

Friction Loss

• Friction loss is the reduction in pressure caused by water turbulence against the hose or pipe walls.