The truth is that most departments still use the interior attack flows from 1 3/4-inch lines for the fully involved structures. Can you knock down the typical fully involved house fire with one of these lines? Yeah, probably in most cases, but how long do you think it will take--two, maybe three minutes or longer? You can add additional lines to the assault to speed up knockdown, but that takes more personnel, who may not be on scene yet, or in some cases, may not be coming at all.
Let’s ask the same question about the low-flow interior lines on the hot fire in a different manner. Why do we not use the big guns (250-, 1,000-gpm flows) on these small structure fires? Some say that an exterior attack with big water flow is the wimpy way to fight fire. Ah yes, prideit’s good to have, but it’s sometimes hazardous to your health. Or how about this one: “The guys don’t like to pull the big hose for the big flows because the lines are too tough to handle, especially with limited personnel.” 3
Well enough of the “why nots.” Let’s start looking to the future and think more progressively. Why should we be using the big flows?
- Protection of civilian life and property: This one is really simple: the faster we put the fire out, the less exposure the victims and property will have.
- Protection of the firefighter: Again, why expose firefighters to such harsh conditions for a prolonged time with inferior flows when a high-flow stream can knock the fire down in seconds?
- Limited personnel: You would think that developing large flow streams from big handlines or master streams would take at least a couple of companies to deploy. Not so! The fact is you can place a high-low handline in service with no more than two firefighters, obtaining flows of up to 600 gpm with a three-inch line. It only takes one firefighter to place a deck-mounted master stream into service.
Limited water supply: Have you ever been on the firelet’s say a fully involved mobile home where the initial attack was started from your 500-gallon booster tank? Now remember, the mobile home is fully involved, which means totally destroyed with no possibility of survival for any occupants who may have been inside. Now, let’s say that a water supply is coming. What is our initial plan of attack? Do we do nothing and wait for the water supply, or start a water-conserving fire attack? More than likely we start the attack using our water as sparingly as possible. This usually means small handlines with small flows. They can either go directly to the fire or be directed to any potential exposure problems.Now think about what usually happens in this type of situation. With the fire at this stage of involvement, the water usually runs out before the fire goes out since the rate of application does not equal the amount of fire involved. This is called “tinkling in the wind.”
Okay, let’s try a different booster tank operation. Let’s hit the fire with everything we possibly can in hopes of blowing the darn thing out. But let’s do it cautiously. One key point to remember is that the tank-to-pump plumbing in the standard fire truck, unless designed to flow more, will only give you 500 gpm. Five hundred gpm from a 500-gallon booster tank allows you one minute of water application before running out. Hit the fire for no more than 30 seconds with a 500-gpm blast. If after 30 seconds the fire has not been knocked down, you still have 250 gallons of water left to hold the fire in check until a water supply is established. You will be surprised at what a 500-gpm stream can do in five to 10 seconds on a well-involved structure fire the size of an average house.4
The moral: Don’t go elephant hunting with a BB gun. Big fires require as big a flow as you can produce to extinguish. The faster they go out, the better off you will be.
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 @aol.com.