When do you stretch Multiple Attack Lines off the First Due Engine on arrival? What is the consumption or cost of charging those lines off tank water? How many Firefighters are needed to operate these lines? Do your firefighters understand when to SHUT down, even if the fire has not been knocked down? We need to THINK in terms of Gallons Per Second when operating off TANK WATER!!
Many organizations do not have good hydrants, large hydrant spacing or no hydrants at all in parts of their jurisdictions. As a matter of fact tank attacks are not even questioned in these circumstances. These organizations usually have 750 gallon and up tanks on their first due engines and commonly quickly provided tank pumped supplies between the first alarm units. I believe it is important to think in gallons per second at all fires, but especially when one must overwhelm the fire rapidly and use as little water as possible.
William E. Clark (Firefighting Principles and Practice) stated “When a fire continues to burn after water has been applied, it is for one of two reasons. Either the water is not reaching the burning material, or it is not being applied at a sufficient rate of flow, The critical flow rate is the minimum flow in gallons per minute needed to extinguish a given fire. A flow greater than the critical rate will extinguish the fire, but a flow less than the critical rate will not. ………… If that rate is not reached or exceeded, the fire will continue to burn.”
The hose lay out above, will provided an overwhelming sufficient flow rate with the 2 1/2 inch line for the fire showing in the picture. The 2 1/2 inch line will provide the critical initial knock out punch for the fire it can reach by rapidly stopping further fire development. The 2 1/2 inch line may only need to be operated for less than a minute. The 2 1/2 inch 250ish GPM line will knock the bulk of the fire and greatly exceed the sufficient flow rate for the fire in the picture above. One must exercise the discipline to shut the nozzle down after the initial knock to conserve water during tank operations. The 2 1/2 inch 250ish GPM line has done it’s job reaching the fire it can. In a 750 gallon tanked pumper this would leave 500 gallons for an interior fire clean up and overhaul push using the 1 3/4 inch line or 150ish GPM attack line.
If at the above fire a crew just stretched a 1 3/4 inch 150ish GPM attack line, it probably would not overwhelm the fire rapidly causing a longer operation time and more water expenditure based on the fact it may not be providing a overwhelmingly sufficient flow rate for rapid fire knock down. In this scenario it may take a few minutes of operation or 450 plus gallons just to achieve the initial knock leaving only 300 gallons in a 750 gallon tank pumper. In my opinion probably not a enough reserve to make a safe attempt at an interior fire clean up and overhaul push.
Applying water that is reaching the burning material from an overwhelming critical rate of flow line, is a vastly superior way to use water. It leads to a more rapid fire knock down and less use of water as long as nozzle discipline is maintained. This is not an opinion piece it is based in the laws of physics. Rapid tank attacks are an efficient way to deal with room and content fires and more in most residential dwellings, the picture above is a good example in my opinion where a rapid knock and interior advance is achievable off the tank supplies of the initial alarm. The key is to rapidly overwhelm the fire with a large GPM line.
Dennis LeGear
PS
Hindsight is 20/20 of course and I know firefighting is dangerous and done in a time compressed task saturated environment, always watch for overhead lines. Perfection is rarely achieved, but should be strived for through knowledge and training on a regular basis.
GPM being flown and tank size are the key considerations. Pulling a second line and depleating the first line is an UP but not back up.
I agree that the initial attack should be done with the Gpm’s overwhelming the Btu’s. As long as you have the manpower to manuver the hose in an efficient way as not to tire your guys before they make the interior push. I also agree that if you can direct the 2 1/2 nozzle stream directly into whats burning or at the main body of fire, then that to me make alot of sense.Nozzle settings and patterns will make all the difference, hopefully the crew is up to date with fire behavior and knowlegable in the dynamics of water applications. Good story, very educational.