Boiled in water tank

[snopes]

Comment: I have heard many times about a man/men being boiled alive in a
water tank where he/they took refuge against a bush fire. Although i have
read this there is never any solid evidence, eg no names no dates no
states where it happened.I find this hard to believe as i would have
thought if the fire was hot enough to boil the water, you would die from
radiation before boiling alive.

[Singing in the Drizzle]

I guess that would depend on the size of the water tank. If it a small storage residential storage tank of say 1,000 gallons there might be a chance of cooking a person in side during a fire. The water does not need to boil to kill a person. The tank would also need to be made of metal and have some way to easily get into it.

Lets see say water need to go from 65 degrees to about 140 degrees to make sure someone is dead on looks cooked (assuming the body is in the water a couple of hours before being found). One pound of water raised 1 degree is 1 BTU and 8.34 pounds of water to a gallon. So raising 1,000 gallons of water 75 degrees would take 625,500 BTUs. I would guess this is well with reason of a hot forest fire. If the tank were say 10,000 gallon I would see this as very unlikely and even more unlikely as the amount of water gets larger.

[Dropbear]

According to the Australian Federal Government's Emergency Management Australia disaster database during a bushfire in 1939:

One victim had climbed into an elevated water tank which, after the fire had passed, was found to have boiled dry.

Most of the material I saw suggested though that the risk was more from breathing in heated air or through overheating as the water got hotter and there was no cooling from the air above.

Dropbear

[Troberg]

I would say that you'd die from smoke inhalation and lack of oxygen before the heat gets you. All in all, I don't think a bush fire would boil a sizable water tank, there simply isn't enough material to burn to create enough heat.

Assuming you have some kind of breathing apparatus, I'd say it's probably one of the safest places to hide.

I also recommend peeing before you get in the tank, just in case.

[Singing in the Drizzle]

So how much water was in the tank?

It takes about 8106.5 BTUs to convert 1 gallon of water to steam once it reaches boiling. That is a lot of heat if the tank had very much water in it.

[Little Galaxy]

I'd agree that a firefront, though intense, would pass far too quickly to heat the volume of water in a tank to boiling point. I've always heard the main danger to be overheating - the water doesn't need to get near boiling point before your body would be unable to cool off.

Unfortunately that would mean that even if you had breathing apparatus it wouldn't help you much...

[DaGuyWitBluGlasses]

Originally Posted by Singing in the Drizzle

So how much water was in the tank?

It takes about 8106.5 BTUs to convert 1 gallon of water to steam once it reaches boiling. That is a lot of heat if the tank had very much water in it.

"The heat released by burning cellulose is approximately 8000 Btu/lb"
http://books.google.com/books?id=QrQ...esult&resnum=1

That's a lot of BTUs available.

This site used an average douglas fir tree to calculate an average mass of 1660 lbs.

I would imagine that a water tower out in the woods would be only a reserve for something small. (EG a national park centre). Thus it wouldn't hold that much water. The wikipedia article on water towers mentions some as small as 5500 imp gallons (6600 US gal)

So just 4 trees could provide enough heat to boil the tank.

[A Turtle Named Mack]

Originally Posted by DaGuyWitBluGlasses

"The heat released by burning cellulose is approximately 8000 Btu/lb"
http://books.google.com/books?id=QrQ...esult&resnum=1

That's a lot of BTUs available.

This site used an average douglas fir tree to calculate an average mass of 1660 lbs.

I would imagine that a water tower out in the woods would be only a reserve for something small. (EG a national park centre). Thus it wouldn't hold that much water. The wikipedia article on water towers mentions some as small as 5500 imp gallons (6600 US gal)

So just 4 trees could provide enough heat to boil the tank.

IF you could get all of that heat to go directly in the tank. However, the radiant heat will radiate all directions, most of the heat will rise by convection, and a tank like that should be placed with the trees cut back away somewhat to prevent damage by falling branches (even without considering fire).

[A Turtle Named Mack]

Originally Posted by Dropbear

Most of the material I saw suggested though that the risk was more from breathing in heated air or through overheating as the water got hotter and there was no cooling from the air above.

Dropbear

But with the air within a wildfire being so extremely dry, I would think the water tank would have very intense evaporation, keeping the heat lower than it might otherwise be, depending on the amount of radiant heat absorbed from the fires. The result of the trade-off would be based whether the fires were close enough to heat the water faster than the enhanced evaporation due to extreme dryness and updrafts would cool it.

So choose a water tank as far from nearby combustibles as possible. Keep your face as low as possible. And I think you would be better off keeping your body wet but out in the air, to take advantage of evaporative cooling. However, on that last point, let you comfort be your guide - if you are getting warmer above the water than in it, even with splashing water over yourself, get down in the tank, as the water will take a lot longer to heat than your exposed body will. As was said above, a wildfire usually passes a particular area relatively quickly, so the tank will probably not heat too awfully when the fire is THAT close to you.

Oh, and watch for falling debris - after inhalation, that may be the biggest hazard in a forest fire or structure fire.

Reminds me of a old version of Grimm's "Brother and Sister" I read in fourth grade when the evil stepmother disguised as a chambermaid boiled the Sister/The Queen alive when giving her a bath.