I come from a rural area where are infrastructures is a generation or two behind what other places 2 counties over have. The part of our infrastructure that affects us the most is water supply. Where some have 42inch mains we at most have 8s and often times all the plugs in a given city are fed by one of those 8 inch mains. In short we have very few hydrants and what hydrants we do have often are very weak, if not broken.
I often hear (as many of you readers likely do as well) about water conservation and the need to make every drop count. We need to make every drop work towards putting out the fire yes?
Than why are we still pulling two and three 1 ¾ inch hand lines when we could have been pulling one 2 ½ and done the same job only faster?
Let’s take a look at the math.
Small Town FD is at a house fire upon arrival the chief notices 50% involvement. The first in engine has 2 cross lays and 1 rear bed of 1 ¾ hose with 150gpm nozzles, and 1 bed of 2 ½ hose with a smoothbore 1 1/8. The engine has a 1500 gallon booster tank and the first in tender is 5 minutes out. What line would supply the biggest bang? Would they run out of water before the tender arrives?
A 1 ¾ line flowing 150GPM’s at 100psi so three of those is 450GPM’s (150gpm x 3 hand lines = 450gpm).
The 2 ½ with the 1 1/8th is flowing 266GPM’s at 50psi
With a 1500 gallon booster tank the chief would run out of water using the 1 ¾ lines in about 3 minutes (1500 gallon booster tank divided by 450gpm = 3.33333 so 3 minutes)
When using the 2 ½ you run out in 5 minutes (1500 divided by 266= 5.639 so 5)
Now some would say your flowing more water with smaller 1 ¾ lines and in total you are but this isn’t Ghostbusters we are not standing there with are “streams” crossing each other to take down the stay puff man. See below.
We always split them up one in the front yard one in the side yard one around back that is what I have always seen (by all means let me know if you do differently I’d like to hear from you) I always hear the “we cant pull the big line because we will run out of water” (we proved that wrong), or I hear the old “ we need more lines for exposure control” (put the fire out and the exposure threat goes away wouldn’t it)?
See the 150gpm steam is not able to penetrate thru the heat to actually reach what is burning it happens. What happens is the stream gets turned to steam and cannot cool the burning material to stop the off gassing which will stop the burning process. It just cools the gases.
Ever been in a flashover chamber?
Same thing you are cooling the gases not what is burning when we pencil the fire. See below
The same can be said for nozzles that are not designed for high flows I have seen nozzles on structure fire lines that are 100psi 125 GPM.
I also hear this “we never use a 2 ½ and we put our fires out”. My next series of questions is this.
*how much water did you go thru?
*how long did it take you?
*what is left standing?
On fires I have been on the answers are as follows
Usually 6 dumps so between 6 and 12,000 gallons at times usually depends.
Some times 30minutes to 1 hour to get it under control.
Again this is 50% involvement style fires.
The argument can be made till the cows come home on which line to pull but in closing think of this.
Wouldn’t more water be conserved if we done the attack correctly and with the right line instead of trying for garden hose flows to save water?And come join us at https://www.facebook.com/#!/groups/1408196186095594/