Master streams typically flow at what minimum GPM?

Master streams are designed to deliver large volumes of water to effectively combat significant fires, typically in commercial or industrial settings. A minimum flow rate of 300 gallons per minute (GPM) is widely recognized as the standard for master streams due to the need to rapidly cool and suppress large fires. This flow rate ensures that the water can reach enough intensity to provide effective fire suppression, particularly in scenarios with high heat release rates or extensive burning surfaces.

In practice, using a master stream—such as a large-diameter hose, aerial device, or portable monitor—enables fire brigades to project water over greater distances and volumes compared to handline operations. Hence, a flow rate of 300 GPM is seen as the baseline for master streams to ensure operational effectiveness and safety for both firefighters and the public.

While other flow rates such as 150 GPM, 200 GPM, or 400 GPM are relevant in various firefighting applications, they do not meet the commonly accepted minimum threshold for master streams to achieve the desired fire control capabilities.