Last month we looked at the domino effect of problems that can be created when improperly advancing a hoseline. This month we will look at the issue of selecting the correct size hoseline.
There are three standard-sized hoselines that the fire service uses as a front line attack line: 1½, 1¾ and 2½ inch. The remaining situations might involve large master streams or deck guns.
The key with selecting the correct size line is quite simply getting the right amount of water on the fire. Select the wrong size from the outset, and the operation will not go as planned.
The problem with Doing what’s familiar
Firefighters tend to fall back upon habits that they may have developed over time due to repetition and familiarity. One habit that most firefighters fall back on is with the 1½- or 1¾-inch hoseline.
These sizes always seem to be the first hoselines pulled for any offensive fire attack. While the 1½- or 1¾-inch hoseline does provide ample water delivery for most of our everyday fires, it falls short when it comes to large fires that require large volumes of water.
The hose coupling diameter of a 1½- and a 1¾-inch are the same, they only differ with the diameter of the hose jacket. So when there is water flowing through a 1¾-inch hoseline, it still has to travel through a 1½-inch coupling at every 50 or 100 feet.
This small reduction in the hose coupling diameter adds some friction loss overall, but the amount is inconsequential in comparison to the amount of water that can be delivered at a lower operating pressure with a 1¾-inch hoseline.
Water to match the fire
The size of the structure, the fire and fuel load being dealt with and the size of the fire, will dictate what size hoseline to be pulled off first and used for effective water delivery. The general rule that most firefighters can remember is small fire equals small water and big fire equals big water.
Small water refers to your basic 1½- or 1¾-inch hoselines; the big water refers to the 2½-inch hoseline.
With a 1½-inch nozzle, the average water delivery rate can be between 150 to 200 gpm. With a 2½-inch nozzle, the water delivery rates can be increased with minimal increase in pump pressure. The average water delivery rates are between 200 and 325 gpm.
This increase in water delivery may be what is needed to achieve a quick and effective knockdown of a large fire. In the accompanying video, you will see examples of where the first hoseline pulled off is the wrong size based upon the size of structure and the fuel load present.
Make sure to not handicap yourself by pulling off the wrong size line.
