Fixed Master Stream Operations Using Smooth Bore TIps

By Paul Shapiro

A master stream is basically defined as a heavy-caliber stream delivered through a master stream water delivery appliance. A master stream is used when flows surpass 350 gallons per minutes (gpm), becoming too difficult to be delivered from a handline operation because of nozzle reaction. The master stream, which is high in flow and usually a straight stream, is produced with a smooth bore tip or some type of combination nozzle.




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There are three types of master stream operations: the fixed master stream, the portable master stream, and the elevated master stream. The following information about master stream smooth bore tips can be found in most fire stream management books in circulation today. It’s information that needs to be understood to establish an information base from which to operate.
The stacked tip is the most common set of smooth bore tips that comes with a master stream. Its name derives from the fact that it consists of four tips connected into one stack, which is then attached to the master stream appliance. The tip sizes and the corresponding flows are based on an 80 pound-per-square inch (psi) nozzle pressure (np).
            1 ⅜-inch            502 gpm
            1 ½-inch            598 gpm
            1 ¾-inch            814 gpm
            2 inch              1,063 gpm
For master stream appliances capable of flows higher than 1,000 gpm, the following tip sizes with 80 psi np will apply. Again, these are the most common.
            2 ¼ inch           1,345 gpm
            2 ½ inch           1,661 gpm
            2 ¾-inch           2,010 gpm
Note that the standard rule is to use a pressure of 80 psi for a smooth bore tip nozzle in master stream operations. Higher pressures will create a broken and insufficient stream and an unstable operation in the elevated and portable modes, according to most fire stream books. Nozzle pressures up to 100 psi can be used only with fixed master stream operations. This column will explain how smooth bore tips can be taken to a much higher level and produce high-pressure streams never thought possible while remaining safe and efficient in all modes of operation.


The purpose of high-pressure smooth bore tip operations used in conjunction with a master stream is to provide the required gpm to extinguish the fire problem with a high-velocity stream that improves the reach and penetration capabilities of the firefighting stream while still maintaining efficient stream performance.

The maximum allowed nozzle pressure for this type of operation is based on the following rules.
Maximum allowed inlet pressure to the master stream appliance. The three master stream appliance most commonly used for the municipal fire service are Task Force Tips, Akron Brass, and Elkhart Brass. Listed below are the specs for each of the three brands of these appliances in the fixed mode.
Task Force Tips, 200 psi inlet pressure–1,250 gpm, 631 nr; 2,000 gpm, 1010 nr
Akron Brass 200 psi inlet pressure–1,250 gpm, 631 nr; 2,000 gpm, 1,010 nr
Elkhart Brass, 200 psi inlet pressure–1,250 gpm, 631 nr; 2,000 gpm, 1,010 nr
I think you will find that most of the other master stream manufacturers require the same 200 psi inlet pressure as well. Always make sure you do not exceed the inlet pressure when performing high-pressure operations.

2. Maximum allowed flow for the master stream appliance.

3. Maximum allowed nozzle reaction for the master stream appliance. This is based on a 100 psi combination nozzle at the rated flow of the appliance. For example, a 1,250 gpm master stream appliance using a 100 psi combination nozzle flowing 1,250 gpm has a nozzle reaction of 631 pounds.

4. Maximum allowed operating pressure for the discharge hose supplying the master stream appliance when applicable. This applies to elevated stream operations using a non-quint truck company and portable master stream operations.

5. Stream angle capabilities for the appliance/apparatus combination.

To provide the required pressure for the high-pressure operation, the pump operator needs to understand the limitations mentioned above and throttle up accordingly. Flow tests will determine what the maximum pressure can be, again based on the above mentioned criteria. A pump chart should then be designed showing all possible pump operations that can be used. The pump operator should plan on throttling up to the maximum allowed predetermined pressure unless something stops him. Does this mean that every time a deck gun operation is placed into service the pump discharge pressure needs to be maxed out? No. The predetermined pump discharge pressure is the number that the pump operator will try to reach unless something stops him.
Some of the things that may stop the operation from going to maximum pressure are the following:
  • Running out of water;
  • Running out of throttle;
  • Running out of revolutions per minute.
  • The stream’s accomplishing its goal;
  • Opposed by other rules set by the department
  • Opposed by orders from the company officer.
The following smooth bore tip sizes with their corresponding nozzle pressure and flows have successfully produced high-velocity/high-flow streams using a master stream. The maximum nozzle reaction for a 1,250 gpm appliance is 631 pounds and for a 2,000 gpm appliance, 1,010 pounds.
            1 ½-inch tip @ 150 psi np =   817 gpm,     530 nr
            1 ¾-inch tip @ 120 psi np =   996 gpm,     577 nr
            1 ¾-inch tip @ 150 psi np = 1,114 gpm,    721 nr
            2-inch tip    @ 100 psi np = 1,189 gpm,    628 nr
            2-inch tip    @ 110 psi np = 1,250 gpm,    691 nr
            2-inch tip    @ 120 psi np = 1,303 gpm,    754 nr
            2-inch tip    @ 140 psi np = 1,407 gpm,    879 nr
            2-inch tip    @ 150 psi np = 1,455 gpm,    942 nr
            2-inch tip    @ 160 psi np = 1,500 gpm, 1,005 nr
Note that the two-inch tip at 160 psi np produced a stream with a footprint reaching 360 feet.
Picture a large fire that has totally consumed the structure where you ended up with a large pile of burning rubble left to be overhauled. This is where the digging power of a high-velocity stream can really have a positive effect. The following smooth bore tip sizes and corresponding nozzle pressures and flows have been successfully used in this type of operation. One point to remember is that the goal in this type of operation is to produce velocity, not high flows.
            1 -inch tip up to 180 psi np = 504 gpm
            1 ¼-inch tip up to 180 psi np = 623 gpm
            1 -inch tip up to 180 psi np = 754 gpm

(2) This deck gun is using a 1¼-inch smooth bore tip flowing 623 gpm at 180 psi np.

Working a brush fire from a fixed master stream appliance is a heck of a lot easier than pulling hose. When possible, a fixed master stream can make very large sweeps in burn areas with the above mentioned high-pressure stream operations. In fact, the 1⅛-inch tip application will more than likely be the tip of choice for this operation.

Paul Shapiro is director of Fire Flow Technology. He is a nationally recognized instructor on large-flow water delivery. He is also a retired engineer from the City of Las Vegas (NV) Fire Department. He has authored numerous articles for fire trade magazines. He has been in the fire service since 1981 and is author of Layin’ the Big Lines and produced the first in a series of videos on large-flow water delivery. He is available to answer questions; he can be reached at (702) 293-5150 or Layinline

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