What is residual pressure in the context of firefighting?

Residual pressure in firefighting refers to the pressure that remains in a hose or piping system after water has been discharged and has overcome resistance caused by factors such as friction and gravity. It is a crucial concept because it helps fire personnel determine how effectively water can be delivered to the fire scene.

When fire hoses are used, the water flow encounters friction along the interior walls of the hose, which reduces the pressure. Additionally, gravity can impact the pressure in the system, particularly if the water is being pumped upward to a higher elevation. Therefore, the residual pressure is essentially what is left over after these challenges to water flow have been accounted for, ensuring that firefighters understand how much pressure is available for effective firefighting operations. This understanding helps in assessing whether the system can deliver adequate water at the required flow rates to combat a fire efficiently.