How much water might you need for an initial knockdown?

[CKirk922]

This question stems from the Hmmm... thread about a department running out of water.

Assume that a non-hydranted home is about 2,200 sq ft and 50-60 percent involved upon arrival...

I realize there are a ton of variables to factor in, but how much water do you reasonably think you will have to have on scene for a somewhat proficient FD to get a knock on this fire?

My FD brings a 1000 gal and 1800 gal engine for first alarm as well as an 1800 gal and 3000 gal tanker on that alarm. We start with 7,600 gallons of water before we need the first M/A tanker to arrive.

I'm looking for your experiences, opinions and typical response information to compare with FDs in my area.

[BKDRAFT]

800 gallons at the most for knockdown.

[The nots so new FNG]

Its hard to say for sure. The configuration of the house/fire as well as method attack (offensive vs defensive).

We bring 1000gal on the 1st CAFS pumper, for non-hydranted, a 3000 gal tanker and then another 1000gal CAFS pumper. If its a working fire, we call for another 3000 gal MA tanker immediately. That puts around 5000 gal on scene very quickly with another 3000 gal coming soon. (plus our tankers 2nd load is another 3000gal). Its always easier to call off the MA tanker than wish you had it.

[AC1503]

A 50-60% involved building will be torn down anyway. Few buildings escape demolition if the fire is not extinguished by the first line and within a couple of minutes.

[efd1524]

BK and AC are right on. <1000 and even that is alot, if the fire is not out in the first few minutes (ie 5min with a 200 GPM nozzle) then the house is a loss. Now don't get me wrong i want the rest of that water as a safety factor when (not if) something goes bad and to stop the big fire and hopefully have items to salvage for the family.

I can tell u from where i work that the last 2 stops we made used <500 and thats with 2 - 200ft. 1 3/4 lines charged.

[FWDbuff]

With CAFS, bulk of the fire knocked down, less than 750.

[Halligan84]

The book answer would be 2200/3 or roughly 750 GPM for fully involved. Take 60% of that number for 1 minute or so and you should have knock down. Again, that would be book answer and no void spaces, partitions, etc...

[CKirk922]

Ok, so far I'm right there with you opinion-wise of If the fire is not out in less than 1000 gallons and if 60% is already involved then it is for all practical senses not salvageable.

Our last two knockdowns took much less than 500 gallons.

Ok, I understand wanting the excess water because MURPHY IS A B**CH factor... But I have seen FDs that will SLOW their water application to the fire just so they don't run out of water.

I DONT BELIEVE that strategy can work... Simple GPMs overwhelming the fire wins the battle. If you slow the GPMs then the fire gains on you, right?

Yes, I know if you run out, it will gain on you anyway.

[Rescue101]

LxWxH divided by 100.Gives you a basic control formula. T.C.

[pvfd27]

But I have seen FDs that will SLOW their water application to the fire just so they don't run out of water.

I question that logic myself. I can see if you have adaquate flow to protect an exposure and not enough for a knock-down. But, that's a different scenerio.

[CKirk922]

I question that logic myself. I can see if you have adaquate flow to protect an exposure and not enough for a knock-down. But, that's a different scenerio.

You hit the nail smack dab on the head. Gotta overwhelm the main body of fire if expect to get anywhere. I think guys in the area are just tactically ignorant; no insult intended. Good fire strategies and solid tactics start with good fire training. Most of us in this county are 15 years behind the times.

Moth to the flame, baby.... Drag too small of a line (maybe two lines) and under pump the lines. Exposures and realistic outcomes are not given the fair consideration they are due. SO.... a lot of water is dribbled away to little effect. The fire continues to grow while they are flowing low gpms, the department cries NEED MORE WATER, and so on and so on. Ok, I'm done with my soapbox now.

[pvfd27]

Always remember, Grasshopper, as with bleeding, all fire stops eventually...

You will eventually have the correct flow for the size of the fire.

[kd7fds]

Rural departments in my area use selectable gallonage nozzles, specifically so they can reduce the flow rate and conserve water on fires.

When you try to talk to them about Fire flow, they uniformly say that only works for people that have hydrants.

Sigh

[CVFD9LT]

I live in a rural area where hydrants are few and far between we had a building off good on the 2nd floor last night 2 out of the 4 rooms completely involved we have a 1200gal cafs pumper first out and a 1,000 pumper 2nd out (if manpower allows it) we knocked both rooms plus the extension in the attic on 1/2 tank out of the cafs pumper in less than 10 minutes with one 2" attack line and a FIXED gallonage tft nozzle

IMO you should need no more than 600 gals of water for an itial knockdown

[DeputyChiefGonzo]

It depends what the contents are. A house with Collyer's mansion conditions will need a "lottah watah" vs. a house that is sparsely furnished.

Of course.. a Fit 5 will knock it down quickly and save the day ....

[Rescue101]

We had a "cottage" the other day,40+ years old on the lake,all matched and finished pine,well inwolved with intrusion into the voids,That took some wah-ta too. T.C.

[kd7fds]

Same rural department called us for mutual aid just this week.

We got on scene, they had used all the water on their first engine, all the water from the first tender and were out of water, about 3000 gallons. They went defensive from the start and were standing in the front yard with 2 1 3/4 lines.

House was maybe 1000 sq ft, 50% involved on arrival.

We had 1000 gallons on board, they wanted us to fill the dump tank with our crosslays, wouldn't really listen to alternative options. We only got about 300 gallons into their tank before the next tender arrived.

Should have used our deck gun to darken it down through the front windows, but they wouldn't allow us to do that.

After knockdown was finally accomplished I watched during overhaul. My guys would find a small spot of fire, hit it for 5 secs with solid stream, shut down, check it out, move to the next spot. In the part of the house they were working in, they used semi-fog, and kept dumping more and more water. One of their officers complained to me how we were wasting water.

Sigh.

[SoloBlitz]

It depends what the contents are. A house with Collyer's mansion conditions will need a "lottah watah" vs. a house that is sparsely furnished.

Of course.. a Fit 5 will knock it down quickly and save the day ....

LMAO!!!

[FyredUp]

Same rural department called us for mutual aid just this week.

We got on scene, they had used all the water on their first engine, all the water from the first tender and were out of water, about 3000 gallons. They went defensive from the start and were standing in the front yard with 2 1 3/4 lines.

House was maybe 1000 sq ft, 50% involved on arrival.

We had 1000 gallons on board, they wanted us to fill the dump tank with our crosslays, wouldn't really listen to alternative options. We only got about 300 gallons into their tank before the next tender arrived.

Should have used our deck gun to darken it down through the front windows, but they wouldn't allow us to do that.

After knockdown was finally accomplished I watched during overhaul. My guys would find a small spot of fire, hit it for 5 secs with solid stream, shut down, check it out, move to the next spot. In the part of the house they were working in, they used semi-fog, and kept dumping more and more water. One of their officers complained to me how we were wasting water.

Sigh.

Your post made the point I was going to make far better than I would have explained it. Tactics and skill level of the particular fire department have a bigger influence on how much water is used than what is burning.

To me this sounds like a fire that if the crews could have made entry with a 1 3/4 line (2 inch in our case) the fire could have rapidly been knocked down, half of this structure should have taken roughly 170 gpm to extinguish. But standing outside may have done little initially but push the fire OR create water damage if the water wasn't anywhere near the fire.

[rescuedawg]

Boiler room fire in private dwelling last week. Cooking upon arrival. One 1 3/4 line , one gallon class A foam, 275 gallons water through the CAFS. Worked perfect. Minimal water damage. Cieling, three engineered beams and some sheetrock walls and exterior siding to repair.