The adjustable fog nozzle is a very popular type of nozzle seen on many apparatus. You will see this type of nozzle used in a wide variety of applications. The adjustable gallonage nozzle offers a lot of versatility because of it's ability to not only change patterns but also to increase and decrease the flow through the nozzle. However, it is very important for firefighters to understand that turning the gallonage adjustment does not necessarily equate to flowing what the actual setting is showing. As you turn the gallonage adjustment on this type of nozzle you are essentially making the orifice larger or smaller and as this adjustment is made the pump operator must compensate on the pump panel to deliver the appropriate nozzle pressure in order to flow the selected gallonage. This nozzle can offer advantages and disadvantages including the flexibility of adjusting the flow but disadvantages like the potential for accidental flow decrease if you bump the gallonage adjustment in the dark or smoke. Take a look at the video below covering Adjustable Gallonage Fog Nozzles:
https://www.youtube.com/watch?v=vS3m5B8Bh9E
