Metal content: A water heater

This site has a downloadable video of an exploding water heater shooting
out of a hole in a field. Powered by a deliberately caused boiling water
eplosion:

http://www.waterheaterblast.com/

It was only a little 12 gallon job, but the tank landed 400 feet away.

It provides a good graphic demonstration for any fool who wonders why
water heaters have to have T&P valves on them and is tempted to replace
a dripping T&P valve with a pipe plug.

Imagine what the explosion of a six times larger 80 gallon water heater
would have looked like.

Enjoy,

Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
"What do you expect from a pig but a grunt?"

"Jeff Wisnia" wrote in message
...
Metal content: A water heater

This site has a downloadable video of an exploding water heater shooting
out of a hole in a field. Powered by a deliberately caused boiling water
eplosion:

Why would you install your water heater in hole?

Simon wrote:

"Jeff Wisnia" wrote in message
...

Metal content: A water heater

This site has a downloadable video of an exploding water heater shooting
out of a hole in a field. Powered by a deliberately caused boiling water
eplosion:


Why would you install your water heater in hole?


Well....Maybe if your home was in a cave?

There once was a hermit named Dave,
Who kept a dead whore in his cave.
He said, "I'll admit,
She smells quite a bit,
But look at the money I save!"

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
"What do you expect from a pig but a grunt?"

Simon wrote:
"Jeff Wisnia" wrote in message
...
Metal content: A water heater

This site has a downloadable video of an exploding water heater
shooting out of a hole in a field. Powered by a deliberately caused
boiling water eplosion:

Why would you install your water heater in hole?

After watching that - you bet! In a very deep hole - far removed from me!

I wonder if your 'average' terrorist is aware of this?

KNOCK KNOCK!!
"yes'
HOMELAND SECURITY!
"and?"
.....WATER HEATER............NO FLY LIST............

Ken.

--
Volunteer your idle computer time for cancer research
http//www.grid.org/download/gold/download.htm
R
My return address is courtesy of Spammotel http://www.spammotel.com/

Ken Davey wrote:

Simon wrote:
"Jeff Wisnia" wrote in message
...
Metal content: A water heater

This site has a downloadable video of an exploding water heater
shooting out of a hole in a field. Powered by a deliberately caused
boiling water eplosion:

Why would you install your water heater in hole?

After watching that - you bet! In a very deep hole - far removed from me!

I wonder if your 'average' terrorist is aware of this?

KNOCK KNOCK!!
"yes'
HOMELAND SECURITY!
"and?"
....WATER HEATER............NO FLY LIST............

Ken.

--
Volunteer your idle computer time for cancer research
http//www.grid.org/download/gold/download.htm
R
My return address is courtesy of Spammotel http://www.spammotel.com/

Fortunately I'm not a terrorist since I though of the hot water as IED
idea a long time ago.

Pete C.

"Jeff Wisnia" wrote in message
...
Metal content: A water heater

This site has a downloadable video of an exploding water heater shooting
out of a hole in a field. Powered by a deliberately caused boiling water
eplosion:

http://www.waterheaterblast.com/

It was only a little 12 gallon job, but the tank landed 400 feet away.

It provides a good graphic demonstration for any fool who wonders why
water heaters have to have T&P valves on them and is tempted to replace a
dripping T&P valve with a pipe plug.

Imagine what the explosion of a six times larger 80 gallon water heater
would have looked like.

Enjoy,

Jeff
I'm trying to imagine. For the sake of argument, would it really be any
greater. The steam is what causes the heater to explode, right? It seems
the heater would explode when a certain pressure was achieved, regardless of
the amount of water heated to begin with. Wouldn't the 80 gallons of water
tend to hold down the remainder of the heater, thus you might get a greater
"flight" from the 12 gallon. I don't believe the entire water contents
would "instantly" become steam and rupture the tank. Now, as I said, I'm
just trying to imagine what would happen...I don't really know and have no
intention of experimenting to find out.

Tom G.

"Tom G" wrote in message
news:VPhug.3599$A8.1918@trnddc02...

"Jeff Wisnia" wrote in message
...
Metal content: A water heater

This site has a downloadable video of an exploding water heater shooting
out of a hole in a field. Powered by a deliberately caused boiling water
eplosion:

http://www.waterheaterblast.com/

It was only a little 12 gallon job, but the tank landed 400 feet away.

It provides a good graphic demonstration for any fool who wonders why
water heaters have to have T&P valves on them and is tempted to replace a
dripping T&P valve with a pipe plug.

Imagine what the explosion of a six times larger 80 gallon water heater
would have looked like.

Enjoy,

Jeff
I'm trying to imagine. For the sake of argument, would it really be any
greater. The steam is what causes the heater to explode, right? It seems
the heater would explode when a certain pressure was achieved, regardless
of the amount of water heated to begin with. Wouldn't the 80 gallons of
water tend to hold down the remainder of the heater, thus you might get a
greater "flight" from the 12 gallon. I don't believe the entire water
contents would "instantly" become steam and rupture the tank. Now, as I
said, I'm just trying to imagine what would happen...I don't really know
and have no intention of experimenting to find out.

Tom G.


I don't know either. I wish I had the info, but I saw where a commercial
water heater blew. It was a larger one, 125-250 gallons, but I don't
remember, but it about destroyed the building it was in and the heater
landed several hundred feet out in the parking lot!
Greg

Tom G wrote:

"Jeff Wisnia" wrote in message
...
Metal content: A water heater

This site has a downloadable video of an exploding water heater shooting
out of a hole in a field. Powered by a deliberately caused boiling water
eplosion:

http://www.waterheaterblast.com/

It was only a little 12 gallon job, but the tank landed 400 feet away.

It provides a good graphic demonstration for any fool who wonders why
water heaters have to have T&P valves on them and is tempted to replace a
dripping T&P valve with a pipe plug.

Imagine what the explosion of a six times larger 80 gallon water heater
would have looked like.

Enjoy,

Jeff
I'm trying to imagine. For the sake of argument, would it really be any
greater. The steam is what causes the heater to explode, right? It seems
the heater would explode when a certain pressure was achieved, regardless of
the amount of water heated to begin with. Wouldn't the 80 gallons of water
tend to hold down the remainder of the heater, thus you might get a greater
"flight" from the 12 gallon. I don't believe the entire water contents
would "instantly" become steam and rupture the tank. Now, as I said, I'm
just trying to imagine what would happen...I don't really know and have no
intention of experimenting to find out.

Tom G.

The steam occurs *after* the tank ruptures, not before. The water under
greater than atmospheric pressure has a higher boiling temperature than
at atmospheric pressure. As the water is heated it expands increasing
the pressure in the sealed tank and further raising it's boiling point.
At some point when the water is well above it's atmospheric boiling
point the pressure is too great for the tank and it ruptures. As soon as
the tank ruptures the pressure returns to atmospheric at which point
*all* of the super heated water instantly flashes into steam with the
resulting massive increase in volume producing the explosive shock wave
similar to chemical explosives. The bigger the tank the more volume of
super heated water to flash into steam.

Pete C.

Tom G wrote:
"Jeff Wisnia" wrote in message
...
Metal content: A water heater

This site has a downloadable video of an exploding water heater shooting
out of a hole in a field. Powered by a deliberately caused boiling water
eplosion:

http://www.waterheaterblast.com/

It was only a little 12 gallon job, but the tank landed 400 feet away.

It provides a good graphic demonstration for any fool who wonders why
water heaters have to have T&P valves on them and is tempted to replace a
dripping T&P valve with a pipe plug.

Imagine what the explosion of a six times larger 80 gallon water heater
would have looked like.

Enjoy,

Jeff
I'm trying to imagine. For the sake of argument, would it really be any
greater. The steam is what causes the heater to explode, right? It seems
the heater would explode when a certain pressure was achieved, regardless of
the amount of water heated to begin with. Wouldn't the 80 gallons of water
tend to hold down the remainder of the heater, thus you might get a greater
"flight" from the 12 gallon. I don't believe the entire water contents
would "instantly" become steam and rupture the tank. Now, as I said, I'm
just trying to imagine what would happen...I don't really know and have no
intention of experimenting to find out.

Tom G.


You'd have 80 gallons of water at, say, 290° and 100 psi pressure (I
haven't looked this up in a steam table, I just guessed.) The water is
still liquid because it's held under pressure*. When the tank blows, it
releases the pressure and all that water turns to steam and expands
rapidly. [That should absorb a lot of energy due to the latent heat of
vaporization, but there must be a huge amount of energy stored in the
superheated water.]

*(the critical temperature of water is about 700°F, above this
temperature water is always a gas regardless of the pressure.)

Bob

Try again...

Your physics is right, but your numbers are wrong. The heat of vaporization
of water is 965 BTU/lb (British Engineering System) or 540 cal/g (cgs
system...). (For sake of completeness, the figure is 2260 kJ/kg).

Jerry


"RoyJ" wrote in message
nk.net...
All of what Pete said except not ALL the water flashes to steam, just a
lot of it. Water holds 1 BTU per pound per degree F, heat of
vaporization is 540 BTU's per pound. So if the unit gets to say 100 psi,
it will be at 338 degrees, and you have 126 BTU's to flash into steam,
or merely 20% of the water goes to steam. But that is more than enough
for serious havoc.

Pete C. wrote:
Tom G wrote:

"Jeff Wisnia" wrote in message
...

Metal content: A water heater

This site has a downloadable video of an exploding water heater
shooting
out of a hole in a field. Powered by a deliberately caused boiling
water
eplosion:

http://www.waterheaterblast.com/

It was only a little 12 gallon job, but the tank landed 400 feet away.

It provides a good graphic demonstration for any fool who wonders why
water heaters have to have T&P valves on them and is tempted to replace
a
dripping T&P valve with a pipe plug.

Imagine what the explosion of a six times larger 80 gallon water heater
would have looked like.

Enjoy,

Jeff

I'm trying to imagine. For the sake of argument, would it really be any
greater. The steam is what causes the heater to explode, right? It
seems
the heater would explode when a certain pressure was achieved,
regardless of
the amount of water heated to begin with. Wouldn't the 80 gallons of
water
tend to hold down the remainder of the heater, thus you might get a
greater
"flight" from the 12 gallon. I don't believe the entire water contents
would "instantly" become steam and rupture the tank. Now, as I said,
I'm
just trying to imagine what would happen...I don't really know and have
no
intention of experimenting to find out.

Tom G.


The steam occurs *after* the tank ruptures, not before. The water under
greater than atmospheric pressure has a higher boiling temperature than
at atmospheric pressure. As the water is heated it expands increasing
the pressure in the sealed tank and further raising it's boiling point.
At some point when the water is well above it's atmospheric boiling
point the pressure is too great for the tank and it ruptures. As soon as
the tank ruptures the pressure returns to atmospheric at which point
*all* of the super heated water instantly flashes into steam with the
resulting massive increase in volume producing the explosive shock wave
similar to chemical explosives. The bigger the tank the more volume of
super heated water to flash into steam.

Pete C.

steamer wrote:
--FWIW the fact that many of these things seem to blow *up* and
land a fair distance from where they started out makes me think the rupture
is beginning at the bottom of the pressure vessel. This might mean the
thing's filled up with crud and has never been drained properly, thus there
is a weak band around the bottom, yes?

The pressure is highest at the bottom.

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

On Sat, 15 Jul 2006 22:07:08 -0500, "Greg O"
wrote:

"Tom G" wrote in message
news:VPhug.3599$A8.1918@trnddc02...

"Jeff Wisnia" wrote in message
...
Metal content: A water heater

This site has a downloadable video of an exploding water heater shooting
out of a hole in a field. Powered by a deliberately caused boiling water
eplosion:

http://www.waterheaterblast.com/

It was only a little 12 gallon job, but the tank landed 400 feet away.

It provides a good graphic demonstration for any fool who wonders why
water heaters have to have T&P valves on them and is tempted to replace a
dripping T&P valve with a pipe plug.

Imagine what the explosion of a six times larger 80 gallon water heater
would have looked like.

Enjoy,

Jeff
I'm trying to imagine. For the sake of argument, would it really be any
greater. The steam is what causes the heater to explode, right? It seems
the heater would explode when a certain pressure was achieved, regardless
of the amount of water heated to begin with. Wouldn't the 80 gallons of
water tend to hold down the remainder of the heater, thus you might get a
greater "flight" from the 12 gallon. I don't believe the entire water
contents would "instantly" become steam and rupture the tank. Now, as I
said, I'm just trying to imagine what would happen...I don't really know
and have no intention of experimenting to find out.

Tom G.


I don't know either. I wish I had the info, but I saw where a commercial
water heater blew. It was a larger one, 125-250 gallons, but I don't
remember, but it about destroyed the building it was in and the heater
landed several hundred feet out in the parking lot!
Greg

In a closed system without pressure relief, the water can get quite a
bit / a lot hotter than 212 without boiling. When the thing does
burst, there would be a lot of pressure released from throughout the
water, I think.

Something sort of like opening a warm 2-liter bottle of soda after
shaking it up

On Sun, 16 Jul 2006 02:50:29 GMT, "Tom G"
wrote:

I'm trying to imagine. For the sake of argument, would it really be any
greater. The steam is what causes the heater to explode, right? It seems
the heater would explode when a certain pressure was achieved, regardless of
the amount of water heated to begin with. Wouldn't the 80 gallons of water
tend to hold down the remainder of the heater, thus you might get a greater
"flight" from the 12 gallon. I don't believe the entire water contents
would "instantly" become steam and rupture the tank. Now, as I said, I'm
just trying to imagine what would happen...I don't really know and have no
intention of experimenting to find out.

If you have the water in the tank under pressure and superheated, as
long as you can maintain the system pressure you are fine. You can
draw off the steam slowly for use. But if the tank ruptures or the
safety valve pops off and the pressure drops a bit, all the water will
try to flash into steam at once - the ratio is 1600 gallons of steam
from one gallon of water.

It WILL turn that tiny rupture into a big one, fast. And if the
safety valve opens but is not big enough to vent the volume of steam
that is developed and wants out (they are rated) the pressure can
quickly spike past the vessel limits and blow the vessel.

You want to see real messes, look back in the history books for
boiler explosions on railroad engines and marine boilers. They can
launch the boiler hundreds of feet up, and level large structures.
This is why boilers and water heaters are not toys.

-- Bruce --

--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545
Spamtrapped address: Remove the python and the invalid, and use a net.

On Sun, 16 Jul 2006 04:54:01 GMT, CJT wrote:

steamer wrote:
--FWIW the fact that many of these things seem to blow *up* and
land a fair distance from where they started out makes me think the rupture
is beginning at the bottom of the pressure vessel. This might mean the
thing's filled up with crud and has never been drained properly, thus there
is a weak band around the bottom, yes?

The pressure is highest at the bottom.

I thought pressure was lighter than air and always rose upwards. Which
is why airplanes fly and blimps float.


Gunner

The aim of untold millions is to be free to do exactly as they choose
and for someone else to pay when things go wrong.

In the past few decades, a peculiar and distinctive psychology
has emerged in England. Gone are the civility, sturdy independence,
and admirable stoicism that carried the English through the war years
.. It has been replaced by a constant whine of excuses, complaints,
and special pleading. The collapse of the British character has been
as swift and complete as the collapse of British power.

Theodore Dalrymple,

In article , "Pete C."
wrote:

Ken Davey wrote:

Simon wrote:
"Jeff Wisnia" wrote in message
...
Metal content: A water heater

This site has a downloadable video of an exploding water heater
shooting out of a hole in a field. Powered by a deliberately caused
boiling water eplosion:

Why would you install your water heater in hole?

After watching that - you bet! In a very deep hole - far removed from me!

I wonder if your 'average' terrorist is aware of this?

KNOCK KNOCK!!
"yes'
HOMELAND SECURITY!
"and?"
....WATER HEATER............NO FLY LIST............

Ken.

--
Volunteer your idle computer time for cancer research
http//www.grid.org/download/gold/download.htm
R
My return address is courtesy of Spammotel http://www.spammotel.com/

Fortunately I'm not a terrorist since I though of the hot water as IED
idea a long time ago.

Pete C.

I'm surprised that in 14 posts, nobody has yet brought up the explosion
vs. BLEVE* distinction.

*Boiling Liquid Expanding Vapor Event

--
Bring back, Oh bring back
Oh, bring back that old continuity.
Bring back, oh, bring back
Oh, bring back Clerk Maxwell to me.

"Gunner" wrote in message
...
On Sun, 16 Jul 2006 04:54:01 GMT, CJT wrote:

steamer wrote:
--FWIW the fact that many of these things seem to blow *up* and
land a fair distance from where they started out makes me think the
rupture
is beginning at the bottom of the pressure vessel. This might mean the
thing's filled up with crud and has never been drained properly, thus
there
is a weak band around the bottom, yes?

The pressure is highest at the bottom.

I thought pressure was lighter than air and always rose upwards. Which
is why airplanes fly and blimps float.


At last! A topic I can contribute to on this NG. First, the pressure is
higher in the bottom when the contents is all liquid. And yes, it is
possible that the crud has corroded a region around or near the bottom. But
the real interesting thing is that with a bigger tank you get a bigger
explosion. Here's why: The state of a gas is determined by pressure,
temperature, quantity of the gas, and the contained volume (remember high
school?). For most gasses, if you increase the pressure enough it will
liquify. Water, or more precisely water vapor, condenses to a liquid under
normal conditions. So the exploding water tank reverses the process. The
water is heated throughout so all the water is heated way above the boiling
point and most importantly, the pressure is not relieved (it builds up, as a
mater of fact). When the tank cracks, even a little, the pressure is
suddenly and dramatically reduced within the tank. ALL of the water flashes
to steam. Worse, now that the water is a gas it continues to expand and
release energy causing more damage (i.e.an explosion). This is why high
pressure systems (3000 psi) are tested with liquid and not air.
Hope this helps.

Tom G wrote:

I'm trying to imagine. For the sake of argument, would it really be any
greater. The steam is what causes the heater to explode, right? It seems
the heater would explode when a certain pressure was achieved, regardless of
the amount of water heated to begin with. Wouldn't the 80 gallons of water
tend to hold down the remainder of the heater, thus you might get a greater
"flight" from the 12 gallon. I don't believe the entire water contents
would "instantly" become steam and rupture the tank. Now, as I said, I'm
just trying to imagine what would happen...I don't really know and have no
intention of experimenting to find out.

Tom G.

The entire contents no. A good portion of it yes. The physics goes
something like this. The water boils producing steam until it begins
the tank rupture, pressure drops and thus more water turns to steam
(boiling point drops as pressure drops). It all happens in an instant
but that is the sequence. Thus the total steam is much more than the
amount present just before the rupture.

There is story about the Stanleyi Steamer and how the brothers tested a
new boiler type in the same way (burying it out in the open). The
design failed.

Harry K

"Gunner" wrote in message
...
On Sun, 16 Jul 2006 04:54:01 GMT, CJT wrote:

steamer wrote:
--FWIW the fact that many of these things seem to blow *up* and
land a fair distance from where they started out makes me think the
rupture
is beginning at the bottom of the pressure vessel. This might mean the
thing's filled up with crud and has never been drained properly, thus
there
is a weak band around the bottom, yes?

The pressure is highest at the bottom.

I thought pressure was lighter than air and always rose upwards. Which
is why airplanes fly and blimps float.


Gunner

The aim of untold millions is to be free to do exactly as they choose
and for someone else to pay when things go wrong.

In the past few decades, a peculiar and distinctive psychology
has emerged in England. Gone are the civility, sturdy independence,
and admirable stoicism that carried the English through the war years
. It has been replaced by a constant whine of excuses, complaints,
and special pleading. The collapse of the British character has been
as swift and complete as the collapse of British power.

Theodore Dalrymple,
pressure is not a "thing" like air or water that can rise or fall.Pressure
is a measurement.
http://en.wikipedia.org/wiki/Pressure

John Husvar wrote:
In article , "Pete C."
wrote:


Ken Davey wrote:

Simon wrote:

"Jeff Wisnia" wrote in message
...

Metal content: A water heater

This site has a downloadable video of an exploding water heater
shooting out of a hole in a field. Powered by a deliberately caused
boiling water eplosion:

Why would you install your water heater in hole?

After watching that - you bet! In a very deep hole - far removed from me!

I wonder if your 'average' terrorist is aware of this?

KNOCK KNOCK!!
"yes'
HOMELAND SECURITY!
"and?"
....WATER HEATER............NO FLY LIST............

Ken.

--
Volunteer your idle computer time for cancer research
http//www.grid.org/download/gold/download.htm
R
My return address is courtesy of Spammotel http://www.spammotel.com/

Fortunately I'm not a terrorist since I though of the hot water as IED
idea a long time ago.

Pete C.


I'm surprised that in 14 posts, nobody has yet brought up the explosion
vs. BLEVE* distinction.

*Boiling Liquid Expanding Vapor Event


Plug "ohio steam engine explosion" into Google for info on a October
2001 accident involving a Case 110 steam tractor boiler failure.

Reportedly only operating in the 50 - 70 PSI range.

Old pictures of steam locomatives having 300 PSI boiler failures are
impressive. Usually caused by someone not paying attention to the water
gauge as I understand it.


Hugh

"Harry K" wrote in message
ups.com...

Tom G wrote:

I'm trying to imagine. For the sake of argument, would it really be any
greater. The steam is what causes the heater to explode, right? It
seems
the heater would explode when a certain pressure was achieved, regardless
of
the amount of water heated to begin with. Wouldn't the 80 gallons of
water
tend to hold down the remainder of the heater, thus you might get a
greater
"flight" from the 12 gallon. I don't believe the entire water contents
would "instantly" become steam and rupture the tank. Now, as I said,
I'm
just trying to imagine what would happen...I don't really know and have
no
intention of experimenting to find out.

Tom G.

The entire contents no. A good portion of it yes. The physics goes
something like this. The water boils producing steam until it begins
the tank rupture, pressure drops and thus more water turns to steam
(boiling point drops as pressure drops). It all happens in an instant
but that is the sequence. Thus the total steam is much more than the
amount present just before the rupture.
Harry K

Now, I have learned something. Saw a story on TV the other day about the
Mississippi Riverboat explosion at the end of the Civil War that killed
about 2500 returning Civil War soldiers and former P.O.Ws. It was
supposedly the worst maritime accident ever but we've forgotten it because
it's importance was lost to the story of the assassination of President
Lincoln. Only a small paragraph or two was reported in the newspapers of
the time.

Tom G.

On Sun, 16 Jul 2006 11:26:52 -0400, "digitalmaster"
wrote:


"Gunner" wrote in message
.. .
On Sun, 16 Jul 2006 04:54:01 GMT, CJT wrote:

steamer wrote:
--FWIW the fact that many of these things seem to blow *up* and
land a fair distance from where they started out makes me think the
rupture
is beginning at the bottom of the pressure vessel. This might mean the
thing's filled up with crud and has never been drained properly, thus
there
is a weak band around the bottom, yes?

The pressure is highest at the bottom.

I thought pressure was lighter than air and always rose upwards. Which
is why airplanes fly and blimps float.


Gunner

The aim of untold millions is to be free to do exactly as they choose
and for someone else to pay when things go wrong.

In the past few decades, a peculiar and distinctive psychology
has emerged in England. Gone are the civility, sturdy independence,
and admirable stoicism that carried the English through the war years
. It has been replaced by a constant whine of excuses, complaints,
and special pleading. The collapse of the British character has been
as swift and complete as the collapse of British power.

Theodore Dalrymple,
pressure is not a "thing" like air or water that can rise or fall.Pressure
is a measurement.
http://en.wikipedia.org/wiki/Pressure


Sigh..I knew I should have added the smilies...but I figured with the
blimp comment...

G

Gunner

The aim of untold millions is to be free to do exactly as they choose
and for someone else to pay when things go wrong.

In the past few decades, a peculiar and distinctive psychology
has emerged in England. Gone are the civility, sturdy independence,
and admirable stoicism that carried the English through the war years
.. It has been replaced by a constant whine of excuses, complaints,
and special pleading. The collapse of the British character has been
as swift and complete as the collapse of British power.

Theodore Dalrymple,

Tom G wrote:
I'm trying to imagine. For the sake of argument, would it really be
any greater. The steam is what causes the heater to explode, right? It
seems the heater would explode when a certain pressure was
achieved, regardless of the amount of water heated to begin with. Wouldn't
the 80 gallons of water tend to hold down the remainder of
the heater, thus you might get a greater "flight" from the 12 gallon.
I don't believe the entire water contents would "instantly" become
steam and rupture the tank. Now, as I said, I'm just trying to
imagine what would happen...I don't really know and have no
intention of experimenting to find out.

It would be much greater.

80 gallons of super-heated water (say 400 degrees) turns to much more steam
(at 212 degrees) than 12 gallons of water when the pressure is relieved.

Yeah! And it was completely blank out on the TV.

Bob Swinney
"Tom G" wrote in message
news:y_tug.1769$RV.1237@trnddc08...

"Harry K" wrote in message
ups.com...

Tom G wrote:

I'm trying to imagine. For the sake of argument, would it really be any
greater. The steam is what causes the heater to explode, right? It
seems
the heater would explode when a certain pressure was achieved,
regardless of
the amount of water heated to begin with. Wouldn't the 80 gallons of
water
tend to hold down the remainder of the heater, thus you might get a
greater
"flight" from the 12 gallon. I don't believe the entire water contents
would "instantly" become steam and rupture the tank. Now, as I said,
I'm
just trying to imagine what would happen...I don't really know and have
no
intention of experimenting to find out.

Tom G.

The entire contents no. A good portion of it yes. The physics goes
something like this. The water boils producing steam until it begins
the tank rupture, pressure drops and thus more water turns to steam
(boiling point drops as pressure drops). It all happens in an instant
but that is the sequence. Thus the total steam is much more than the
amount present just before the rupture.
Harry K

Now, I have learned something. Saw a story on TV the other day about the
Mississippi Riverboat explosion at the end of the Civil War that killed
about 2500 returning Civil War soldiers and former P.O.Ws. It was
supposedly the worst maritime accident ever but we've forgotten it because
it's importance was lost to the story of the assassination of President
Lincoln. Only a small paragraph or two was reported in the newspapers of
the time.

Tom G.

In rec.crafts.metalworking sky wrote:

John Husvar wrote:
In article , "Pete C."
wrote:

Ken Davey wrote:

Simon wrote:
"Jeff Wisnia" wrote in message
...
Metal content: A water heater

This site has a downloadable video of an exploding water heater
shooting out of a hole in a field. Powered by a deliberately caused
boiling water eplosion:

Why would you install your water heater in hole?

After watching that - you bet! In a very deep hole - far removed from me!

I wonder if your 'average' terrorist is aware of this?

KNOCK KNOCK!!
"yes'
HOMELAND SECURITY!
"and?"
....WATER HEATER............NO FLY LIST............

Ken.

--
Volunteer your idle computer time for cancer research
http//www.grid.org/download/gold/download.htm
R
My return address is courtesy of Spammotel http://www.spammotel.com/

Fortunately I'm not a terrorist since I though of the hot water as IED
idea a long time ago.

Pete C.

I'm surprised that in 14 posts, nobody has yet brought up the explosion
vs. BLEVE* distinction.

*Boiling Liquid Expanding Vapor Event

--
Bring back, Oh bring back
Oh, bring back that old continuity.
Bring back, oh, bring back
Oh, bring back Clerk Maxwell to me.


John Husvar....... or is that John Henry?........ You beat me to
it.........

Following courtesy of Peter van der Linden:

You'd better "BLEVE" it
Water turning to steam expands 1600 times in volume -- so 2000 gallons
of water instantly vaporises to 3 million gallons of steam! It's
confined in a metal tube which bursts explosively. The vast majority of
boiler explosions are actually firebox failures caused by too little
water. These often happen when crossing the summit of a hill. As the
grade changes, water surges away from the crown sheet.

See.......... http://afu.com/steam/ ........ for
picture..............

A boiler explosion broke this locomotive into small pieces
and sprayed them, and the crew, over a wide area of Florida.

The process of hot pressurized water turning into steam can be seen on
any car. It's the reason radiators have the warning "don't unscrew this
cap while the engine is hot". If you ignore the warning, and unscrew
the cap, the pressurized water inside will vaporize and steam up in
your face. Casualty departments, police charge sheets, and physics
professors refer to this as a BLEVE - Boiling-Liquid Expanding-Vapor
Explosion. It also happens when students try to sneak some dry ice out
of the lab in a screw-top soda bottle.

An exploding pop bottle is just gas pressure. At no point is a pop bottle
going to reach over 800PSI inside to liquify CO2.

Jeff Wisnia wrote:
Metal content: A water heater

This site has a downloadable video of an exploding water heater shooting
out of a hole in a field. Powered by a deliberately caused boiling water
eplosion:

http://www.waterheaterblast.com/

It was only a little 12 gallon job, but the tank landed 400 feet away.

It provides a good graphic demonstration for any fool who wonders why
water heaters have to have T&P valves on them and is tempted to replace
a dripping T&P valve with a pipe plug.

Imagine what the explosion of a six times larger 80 gallon water heater
would have looked like.

Enjoy,

Jeff

Isn't it wonderful that I live in a place where
they don't put all sorts of safety stuff in the
lines. If my water heater overheats, the pressure
just equalizes with the incoming cold water line
since there are no restriction between the water
tank to the street water supply.

First the water tank would boil and the pressure
would push the water back in the cold water line.
When the boiling water level dropped to the
upper electrode, the electrode would burn out,
possibly turning the power off, but if not, the
water would continue to boil until the lower
electrode was uncovered which at that time the
electrode would burn out and coldwater would fill
the tank.

Of course if I had a gas heater (which I do now),
it would just boil dry and then the bottom would
burn out and cold water would poor in.

I wouldn't notice anything until the water flooded.

I'll bet way more people are killed by lightening
each year than by an exploding water tank.
Probably about 10,000 to 1 more by lightening.

George E. Cawthon wrote:
Jeff Wisnia wrote:
Metal content: A water heater

This site has a downloadable video of an exploding water heater
shooting out of a hole in a field. Powered by a deliberately caused
boiling water eplosion:

http://www.waterheaterblast.com/

It was only a little 12 gallon job, but the tank landed 400 feet away.

It provides a good graphic demonstration for any fool who wonders why
water heaters have to have T&P valves on them and is tempted to
replace a dripping T&P valve with a pipe plug.

Imagine what the explosion of a six times larger 80 gallon water
heater would have looked like.

Enjoy,

Jeff

Isn't it wonderful that I live in a place where they don't put all sorts
of safety stuff in the lines. If my water heater overheats, the
pressure just equalizes with the incoming cold water line since there
are no restriction between the water tank to the street water supply.

First the water tank would boil and the pressure would push the water
back in the cold water line. When the boiling water level dropped to
the upper electrode, the electrode would burn out, possibly turning the
power off, but if not, the water would continue to boil until the lower
electrode was uncovered which at that time the electrode would burn out
and coldwater would fill the tank.

Of course if I had a gas heater (which I do now), it would just boil dry
and then the bottom would burn out and cold water would poor in.

I wouldn't notice anything until the water flooded.

I'll bet way more people are killed by lightening each year than by an
exploding water tank. Probably about 10,000 to 1 more by lightening.



I've wondered the same thing. You'd have to have a closed valve (or a
check valve) before the water heater tank and all the hot water faucets
closed to get in trouble. But if it ever did BLEVE, there's a *lot* of
energy released.

Bob

Tom G wrote:



I'm trying to imagine. For the sake of argument, would it really be any
greater. The steam is what causes the heater to explode, right? It seems
the heater would explode when a certain pressure was achieved, regardless of
the amount of water heated to begin with. Wouldn't the 80 gallons of water
tend to hold down the remainder of the heater, thus you might get a greater
"flight" from the 12 gallon. I don't believe the entire water contents
would "instantly" become steam and rupture the tank. Now, as I said, I'm
just trying to imagine what would happen...I don't really know and have no
intention of experimenting to find out.

Tom G.


Similar to the dynamics of a locomotive boiler going. The initial
rupture is of enough violence to releive the pressure on the remainder
of the superheated water in the boiler. When it all goes to steam at the
same time, it becomes something that one would rather read about than
experience.
Part of the design of safety valves looks at limiting the rate that
pressure is releived for that purpose.

Cheers
Trevor Jones

"zxcvbob" wrote in message
...
George E. Cawthon wrote:
Jeff Wisnia wrote:
Metal content: A water heater

This site has a downloadable video of an exploding water heater shooting
out of a hole in a field. Powered by a deliberately caused boiling water
eplosion:

http://www.waterheaterblast.com/

It was only a little 12 gallon job, but the tank landed 400 feet away.

It provides a good graphic demonstration for any fool who wonders why
water heaters have to have T&P valves on them and is tempted to replace
a dripping T&P valve with a pipe plug.

Imagine what the explosion of a six times larger 80 gallon water heater
would have looked like.

Enjoy,

Jeff

Isn't it wonderful that I live in a place where they don't put all sorts
of safety stuff in the lines. If my water heater overheats, the pressure
just equalizes with the incoming cold water line since there are no
restriction between the water tank to the street water supply.

First the water tank would boil and the pressure would push the water
back in the cold water line. When the boiling water level dropped to
the upper electrode, the electrode would burn out, possibly turning the
power off, but if not, the water would continue to boil until the lower
electrode was uncovered which at that time the electrode would burn out
and coldwater would fill the tank.

Of course if I had a gas heater (which I do now), it would just boil dry
and then the bottom would burn out and cold water would poor in.

I wouldn't notice anything until the water flooded.

I'll bet way more people are killed by lightening each year than by an
exploding water tank. Probably about 10,000 to 1 more by lightening.



I've wondered the same thing. You'd have to have a closed valve (or a
check valve) before the water heater tank and all the hot water faucets
closed to get in trouble. But if it ever did BLEVE, there's a *lot* of
energy released.

Bob


So you could trigger the explosion opening any faucet, hot or cold?

I do not know about check valves but most utility have a antysiphoning
valve, should not that vent as the pressure rise above the main?

Not trying to imply the T&P is not necessary, just want to understand all
the physic involved.

Mauro

"zxcvbob" wrote in message
...
George E. Cawthon wrote:
Jeff Wisnia wrote:
Metal content: A water heater

This site has a downloadable video of an exploding water heater shooting
out of a hole in a field. Powered by a deliberately caused boiling water
eplosion:

http://www.waterheaterblast.com/

It was only a little 12 gallon job, but the tank landed 400 feet away.

It provides a good graphic demonstration for any fool who wonders why
water heaters have to have T&P valves on them and is tempted to replace
a dripping T&P valve with a pipe plug.

Imagine what the explosion of a six times larger 80 gallon water heater
would have looked like.

Enjoy,

Jeff

Isn't it wonderful that I live in a place where they don't put all sorts
of safety stuff in the lines. If my water heater overheats, the pressure
just equalizes with the incoming cold water line since there are no
restriction between the water tank to the street water supply.

First the water tank would boil and the pressure would push the water
back in the cold water line. When the boiling water level dropped to
the upper electrode, the electrode would burn out, possibly turning the
power off, but if not, the water would continue to boil until the lower
electrode was uncovered which at that time the electrode would burn out
and coldwater would fill the tank.

Of course if I had a gas heater (which I do now), it would just boil dry
and then the bottom would burn out and cold water would poor in.

I wouldn't notice anything until the water flooded.

I'll bet way more people are killed by lightening each year than by an
exploding water tank. Probably about 10,000 to 1 more by lightening.



I've wondered the same thing. You'd have to have a closed valve (or a
check valve) before the water heater tank and all the hot water faucets
closed to get in trouble. But if it ever did BLEVE, there's a *lot* of
energy released.

Bob


Many municipal water suppliers run over 100 psi, thus requiring each home to
have a pressure reducer where the water line enters the home. The pressure
reducer would act as a closed valve to a higher downstream pressure.

Shawn

You assume electric. Ok - does the stove top or oven element burn out ?
It is the same material - cal rod.

Many places have anti-back flow devices at the street so some dufus doesn't
set up a sprayer of some agent orange class of material to spray bugs or
such - and siphon it into the water system. If the dufus doesn't have his
own on the hose line, he will do himself/themselves in.

Which then means another valve in the house must be open to take the expansion.

How about gas ?

Martin
Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH & Endowment Member
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member
http://lufkinced.com/



George E. Cawthon wrote:
Jeff Wisnia wrote:

Metal content: A water heater

This site has a downloadable video of an exploding water heater
shooting out of a hole in a field. Powered by a deliberately caused
boiling water eplosion:

http://www.waterheaterblast.com/

It was only a little 12 gallon job, but the tank landed 400 feet away.

It provides a good graphic demonstration for any fool who wonders why
water heaters have to have T&P valves on them and is tempted to
replace a dripping T&P valve with a pipe plug.

Imagine what the explosion of a six times larger 80 gallon water
heater would have looked like.

Enjoy,

Jeff


Isn't it wonderful that I live in a place where they don't put all sorts
of safety stuff in the lines. If my water heater overheats, the
pressure just equalizes with the incoming cold water line since there
are no restriction between the water tank to the street water supply.

First the water tank would boil and the pressure would push the water
back in the cold water line. When the boiling water level dropped to
the upper electrode, the electrode would burn out, possibly turning the
power off, but if not, the water would continue to boil until the lower
electrode was uncovered which at that time the electrode would burn out
and coldwater would fill the tank.

Of course if I had a gas heater (which I do now), it would just boil dry
and then the bottom would burn out and cold water would poor in.

I wouldn't notice anything until the water flooded.

I'll bet way more people are killed by lightening each year than by an
exploding water tank. Probably about 10,000 to 1 more by lightening.

----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

Martin H. Eastburn wrote:
...
Many places have anti-back flow devices at the street ...

I don't know how many "many" is but I would say that many do not. I say
this because heater installation instructions call for a vacuum breaker
on the supply line. This prevent tank collapse if water is sucked out
the supply line, as when a fire truck is pulling water from a hydrant.
In this case water is flowing "backwards" to the street.

My $.02,
Bob

MG wrote:
"zxcvbob" wrote in message
...
George E. Cawthon wrote:
snip

I've wondered the same thing. You'd have to have a closed valve (or a
check valve) before the water heater tank and all the hot water faucets
closed to get in trouble. But if it ever did BLEVE, there's a *lot* of
energy released.

Bob


So you could trigger the explosion opening any faucet, hot or cold?

--------------------------------
Not likely IMO as the explosion is caused by a sudden rupture of the
tank, If the rupture hasn't happened before you open the faucet,
opening it only reduces the pressure. Yes, more steam will be released
as the pressure drops but the pressure is coming down.
---------------------------------
I do not know about check valves but most utility have a antysiphoning
valve, should not that vent as the pressure rise above the main?

Not trying to imply the T&P is not necessary, just want to understand all
the physic involved.

Mauro

Any house sytem with a PRV (pressure reducing valve) or on a well
system will be a closed system with nowhere for excess pressure to
bleed off.

Anti siphoning vavles open when a pressure -drop- occurs. They
wouldn't open on a rise in pressure.

Harry K

In article ,
Hugh Prescott wrote:


Plug "ohio steam engine explosion" into Google for info on a October
2001 accident involving a Case 110 steam tractor boiler failure.

No need, thanks. I live nearby. (Akron)

Serious accident alright; five killed, many injuries.


Reportedly only operating in the 50 - 70 PSI range.

Old pictures of steam locomatives having 300 PSI boiler failures are
impressive. Usually caused by someone not paying attention to the water
gauge as I understand it.


Hugh

--
Bring back, Oh bring back
Oh, bring back that old continuity.
Bring back, oh, bring back
Oh, bring back Clerk Maxwell to me.

zxcvbob wrote:
George E. Cawthon wrote:
Jeff Wisnia wrote:
Metal content: A water heater

This site has a downloadable video of an exploding water heater
shooting out of a hole in a field. Powered by a deliberately caused
boiling water eplosion:

http://www.waterheaterblast.com/

It was only a little 12 gallon job, but the tank landed 400 feet away.

It provides a good graphic demonstration for any fool who wonders why
water heaters have to have T&P valves on them and is tempted to
replace a dripping T&P valve with a pipe plug.

Imagine what the explosion of a six times larger 80 gallon water
heater would have looked like.

Enjoy,

Jeff

Isn't it wonderful that I live in a place where they don't put all
sorts of safety stuff in the lines. If my water heater overheats, the
pressure just equalizes with the incoming cold water line since there
are no restriction between the water tank to the street water supply.

First the water tank would boil and the pressure would push the water
back in the cold water line. When the boiling water level dropped to
the upper electrode, the electrode would burn out, possibly turning
the power off, but if not, the water would continue to boil until the
lower electrode was uncovered which at that time the electrode would
burn out and coldwater would fill the tank.

Of course if I had a gas heater (which I do now), it would just boil
dry and then the bottom would burn out and cold water would poor in.

I wouldn't notice anything until the water flooded.

I'll bet way more people are killed by lightening each year than by an
exploding water tank. Probably about 10,000 to 1 more by lightening.



I've wondered the same thing. You'd have to have a closed valve (or a
check valve) before the water heater tank and all the hot water faucets
closed to get in trouble. But if it ever did BLEVE, there's a *lot* of
energy released.

Bob


I would bet that in most cases a hot water line
would fail before the tank, especially in the
supply line to faucets which are rubber hose,
skinny metal, or plastic.

MG wrote:
"zxcvbob" wrote in message
...
George E. Cawthon wrote:
Jeff Wisnia wrote:
Metal content: A water heater

This site has a downloadable video of an exploding water heater shooting
out of a hole in a field. Powered by a deliberately caused boiling water
eplosion:

http://www.waterheaterblast.com/

It was only a little 12 gallon job, but the tank landed 400 feet away.

It provides a good graphic demonstration for any fool who wonders why
water heaters have to have T&P valves on them and is tempted to replace
a dripping T&P valve with a pipe plug.

Imagine what the explosion of a six times larger 80 gallon water heater
would have looked like.

Enjoy,

Jeff
Isn't it wonderful that I live in a place where they don't put all sorts
of safety stuff in the lines. If my water heater overheats, the pressure
just equalizes with the incoming cold water line since there are no
restriction between the water tank to the street water supply.

First the water tank would boil and the pressure would push the water
back in the cold water line. When the boiling water level dropped to
the upper electrode, the electrode would burn out, possibly turning the
power off, but if not, the water would continue to boil until the lower
electrode was uncovered which at that time the electrode would burn out
and coldwater would fill the tank.

Of course if I had a gas heater (which I do now), it would just boil dry
and then the bottom would burn out and cold water would poor in.

I wouldn't notice anything until the water flooded.

I'll bet way more people are killed by lightening each year than by an
exploding water tank. Probably about 10,000 to 1 more by lightening.


I've wondered the same thing. You'd have to have a closed valve (or a
check valve) before the water heater tank and all the hot water faucets
closed to get in trouble. But if it ever did BLEVE, there's a *lot* of
energy released.

Bob


So you could trigger the explosion opening any faucet, hot or cold?

I do not know about check valves but most utility have a antysiphoning
valve, should not that vent as the pressure rise above the main?

Not trying to imply the T&P is not necessary, just want to understand all
the physic involved.

Mauro



I don't know that "most" utilities have an
antisiphon valve. I don't know that "most"
utilities have any restriction. In fact, I don't
know what "most" utilities do. But I know that
there are utilities in various places that have no
restriction in the incoming line. And if there
are no restriction then then a T&P valve is just
another possible failure point.

But obviously if there are backflow preventers of
any kind, you would be foolish to not have a T&P
valve.

Martin H. Eastburn wrote:
You assume electric. Ok - does the stove top or oven element burn out ?
It is the same material - cal rod.
I didn't assume electric, I specifically mentioned
what would happen with electric and what would
happen with gas.

Of course electric elements in water heaters burn
out. Why do you think the manufacturer's
instructions always caution you to fill the tank
with water before turning on the power?


Many places have anti-back flow devices at the street so some dufus doesn't
set up a sprayer of some agent orange class of material to spray bugs or
such - and siphon it into the water system. If the dufus doesn't have his
own on the hose line, he will do himself/themselves in.

Certainly some do, what is your point? No
backflow preventers in my lines, In fact, I don't
believe I have ever lived in a house that had a
backflow preventer at the city, county, or
whatever water line.


Which then means another valve in the house must be open to take the
expansion.

How about gas ?

I think I covered that!


Martin
Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH & Endowment Member
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member
http://lufkinced.com/



George E. Cawthon wrote:
Jeff Wisnia wrote:

Metal content: A water heater

This site has a downloadable video of an exploding water heater
shooting out of a hole in a field. Powered by a deliberately caused
boiling water eplosion:

http://www.waterheaterblast.com/

It was only a little 12 gallon job, but the tank landed 400 feet away.

It provides a good graphic demonstration for any fool who wonders why
water heaters have to have T&P valves on them and is tempted to
replace a dripping T&P valve with a pipe plug.

Imagine what the explosion of a six times larger 80 gallon water
heater would have looked like.

Enjoy,

Jeff


Isn't it wonderful that I live in a place where they don't put all
sorts of safety stuff in the lines. If my water heater overheats, the
pressure just equalizes with the incoming cold water line since there
are no restriction between the water tank to the street water supply.

First the water tank would boil and the pressure would push the water
back in the cold water line. When the boiling water level dropped to
the upper electrode, the electrode would burn out, possibly turning
the power off, but if not, the water would continue to boil until the
lower electrode was uncovered which at that time the electrode would
burn out and coldwater would fill the tank.

Of course if I had a gas heater (which I do now), it would just boil
dry and then the bottom would burn out and cold water would poor in.

I wouldn't notice anything until the water flooded.

I'll bet way more people are killed by lightening each year than by an
exploding water tank. Probably about 10,000 to 1 more by lightening.

----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet
News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+
Newsgroups
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Bob Engelhardt wrote:
Martin H. Eastburn wrote:
...
Many places have anti-back flow devices at the street ...

I don't know how many "many" is but I would say that many do not. I say
this because heater installation instructions call for a vacuum breaker
on the supply line. This prevent tank collapse if water is sucked out
the supply line, as when a fire truck is pulling water from a hydrant.
In this case water is flowing "backwards" to the street.

My $.02,
Bob

I have never seen a vacuum break on a water supply
line to a hot water tank, and it sounds completely
useless.

First if your fire truck scenario even worked, it
would be the responsibility of the water system to
install backflow preventers at the turnouts to the
houses. Second, collapse of a tank is virtually
impossible because I don't know how you would be
able to suck the water out through the supply
line. Water has a relatively low adhesion rate,
so a strong enough pull (vacuum) would break the
water column.

Second, if hot water tank lines did have vacuum
breaks and there were no back flow preventers and
the firetruck made the water flow "backwards,"
then the truck would soon be pumping water and air.

What would happen to the water if one end of a
tangled system of pipes filled with water is
closed and a strong vacuum is put on the other
end? Nothing significant. Yes if you got a low
enough pressure the water would boil and vapor
would be slowly drawn off.

You are not going to crush a water tank (or any
part of your water system) by putting a vacuum on
the system.

Bob Engelhardt wrote:
Martin H. Eastburn wrote:
...
Many places have anti-back flow devices at the street ...

I don't know how many "many" is but I would say that many do not. I say
this because heater installation instructions call for a vacuum breaker
on the supply line. This prevent tank collapse if water is sucked out
the supply line, as when a fire truck is pulling water from a hydrant.
In this case water is flowing "backwards" to the street.

My $.02,
Bob

Bob
Unless we are using hard suction hose we cannot draw the pressure down
below about five pounds before the hose will collapse and stop the flow.
Even with "Hard Sleeve" the maximum pressure reduction a modern fire
pumper in good condition can achieve is roughly two thirds of
atmospheric. Would negative ten pounds actually collapse a water heater
tank?
--
Tom Horne

Well we aren't no thin blue heroes and yet we aren't no blackguards to.
We're just working men and woman most remarkable like you.

George E. Cawthon wrote:
I have never seen a vacuum break on a water supply line to a hot water
tank, and it sounds completely useless.

I have seen plenty of them. As to "useless", I can't personally say.

First if your fire truck scenario even worked, it would be the
responsibility of the water system to install backflow preventers at the
turnouts to the houses.

Yeah, right.

Second, collapse of a tank is virtually
impossible because I don't know how you would be able to suck the water
out through the supply line. Water has a relatively low adhesion rate,
so a strong enough pull (vacuum) would break the water column.

Second, if hot water tank lines did have vacuum breaks and there were no
back flow preventers and the firetruck made the water flow "backwards,"
then the truck would soon be pumping water and air.

What would happen to the water if one end of a tangled system of pipes
filled with water is closed and a strong vacuum is put on the other
end? Nothing significant. Yes if you got a low enough pressure the
water would boil and vapor would be slowly drawn off.

Don't take "vacuum" too literally. They would more accurately be called
"negative pressure preventers". They let air in as soon as the water
pressure is less than atmospheric. So there is still absolute positive
pressure in the pipe and on the water.

You are not going to crush a water tank (or any part of your water
system) by putting a vacuum on the system.

Water heaters are designed to hold pressure. It is very easy for a thin
wall tank to hold pressure (e.g., soda bottle). A thin wall does not
hold negative pressure ("vacuum") at all. I don't have figures, but I
would guess that a couple of psi would crush a tank. For example, a
tank 50" high and 30" in circumference has an area of 1500 sq in. 1 psi
would exert 1500 pounds force on the tank.

Awaiting an experienced reply,
Bob

Water heaters are designed to hold pressure. It is very easy for a thin
wall tank to hold pressure (e.g., soda bottle). A thin wall does not hold
negative pressure ("vacuum") at all. I don't have figures, but I would
guess that a couple of psi would crush a tank. For example, a tank 50"
high and 30" in circumference has an area of 1500 sq in. 1 psi would
exert 1500 pounds force on the tank.

Awaiting an experienced reply,
Bob

Done it (intentionally).

My son and I cleared out an old shack of a house preparatory to salvaging
the ancient pine floors and joists.
Just for fun, (on the excuse it would make more room in the trailer on the
way to the scrap yard) we collapsed both a water heater and a water pressure
tank with a cheap 115v vane pump. The water heater was disappointing. We
_heard_ it collapse, and saw some distortions in the outer casing, but
didn't see the tank squinch down, because the inner tank wasn't hard-coupled
to the outer housing. The pressure tank almost didn't go with the limited
vacuum we could pull; but finally it caved -- rather suddenly. The water
tank was origianlly almost "square"; the heater tank had a very narrow
width-to-height profile.

I've used water heater tanks for building furnaces and barbeques. The metal
is quite thin.

LLoyd