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Master Stream Operations: Bringing In the Big Guns

Fixed Master Stream Operations, Give Me Volume or Give Me Velocity

The fixed master stream is a master stream appliance mounted via discharge plumbing to the top of the fire apparatus. It can be either permanently secured with bolts or removable so that it can be placed in the portable mode.

There are several makes of fixed master stream appliances used in the municipal fire service that use both combination and smooth bore nozzles and have flow capabilities ranging from 50 GPM to 2000 GPM at nozzle pressures more commonly ranging from 80 to 100 PSI. There are two basic types of fixed master stream appliances. The first one, which is the smaller of the two, is rated to flow up to 1250 GPM and works best when supplied with 3" discharge plumbing.

Most makes of the 1250 GPM monitor can be moved and placed into the portable mode. The second and larger master stream appliance is rated to go to 2000 GPM. This appliance is permanently fixed to the discharge plumbing, which is 4" in diameter.

Now that the basics has been covered, new and more progressive information not found in the standard fire stream books will be introduced. Keep in mind that everything that is going to be read has been deemed safe by the manufacturers of the equipment being used. There are two basic rules that need to be followed during fixed master stream operations. They are: “Be Safe” and “Produce the Required Stream.”


Let’s talk about safety first. If the fixed gun being used is the type that can be detached and placed on the ground as a portable, remember to check the attachment device from the appliance to the discharging plumbing flange from the pump to be sure that the monitor appliance is in fact attached properly. There have been accidents that have resulted from improper connections at this point. The master stream appliance should be installed in accordance with the manufacturer’s specifications.

A regular maintenance check should be done on the discharge plumbing leading to the appliance as well as the brackets holding the plumbing in place. Corrosion can weaken and cause the plumbing and brackets to fail during the master stream operation, which will most likely be catastrophic. The operator of the fixed master stream appliance should never stand above it in case of failure. Always stand to the side reaching out to direct the appliance as needed.

The firefighter stands on the back side keeping him away from the appliance should it fail.

Finally, never exceed the maximum operating flow, nozzle reaction, and pressure of the appliance being used. More will be said about this later in this section.

Producing the Best Possible Stream

Producing the best possible stream for the job at hand can require several things. The first thing that needs to be known is the type of job the stream is going to be required to handle. Is the fire problem a high volume defensive-type fire? Or is it a quick attack offensive fire (Blitz attack)?

Is the water supply going to be coming from a hydrant system or will the booster tank be used? Are operations limited to large volume streams when using a master stream appliance? What about a low volume stream used for overhaul purposes or possibly a brush fire scenario where large volumes of water are not required for extinguishment? The list goes on and on.

The defensive high volume master stream operations are pretty basic. The goal is to lob as much water as possible onto the fire. Smooth bore tips as well as combination nozzles are well suited for the job. When using smooth bore tips, it is important to remember to choose the proper tip size to match the available water supply.

Just to refresh the memory, these tips have rated flows based on 80 PSI nozzle pressure. The same holds true for the selectable gallonage and fixed gallonage nozzles within their pressure range. The automatic nozzles will be able to adjust their stream quality to match the corresponding water supply availability based on a near constant nozzle pressure.

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