I have to say I really enjoyed this myth, thanks again guys for a great program.

As many have said this is a very serious and real threat but the the reality is it doesn't take an incorrect installation to have this happen. My parents home had this issue and only by luck am I alive.

When I was younger lad I was sleeping in the late afternoon, when my mother came home, I awoke to "whats on fire". After few tense quick thinking minutes we switched off the power to the house, dialed 911 and waited. Not knowing what the problem was the fire department arrived in sub 5 min (Thank you to all firefighters). They determined that the water heaters insulation was the problem that the thermostat failed in the on position and the heat was cooking off the dust in the insulation. They left and we went back to survey the problem. No one, neither us nor the firefighters had any idea just how dangerous the situation was. We approached the failed tank and after a few moments realized the hissing sound we could faintly hear was coming from a join on one of the cold water pipes. I told my mom to get out now! She was clueless as to the danger but did go upstairs. Knowing the dangers of having 40+ gallons of water flash to steam I felt I had to do something. I turned on the water on at the tap upstairs, instantly steam shot out everywhere, filled the house with a thick cloud of vapor. After 45 minuets of rain inside the house caused by the steam. Water finally came out of the tap.

It took a few days to get the house re plumbed and clean up from the adventure.
The pipes needed replacement because of stress, all of the fixtures even the toilet and any part attached to the plumbing had to be replaced. The funny thing is that the toilets innards were plastic and rubber, they melted but no steam came out of them. Even the water meeter to the house had to be replaced because the plastic gears inside had melted. (for use for cold water only, go figure)

We contacted the fire department and alert them to what happened. They requested we send off the pressure release valve for analysis. The cause was neglect, apparently your suppose to test the valve on occasion. It was determined that because the sacrificial anode had been depleted it allowed a chemical reaction that could have sealed the valve, or from mineral buildup inside the tank to flake off and sealed the valve shut rendering it useless. When the thermostat failed due to years of use it failed stuck in the on position. It was primed to do exactly what you saw on this myth.

It turned out the only pressure release in the system was the old water meeter, it didn't have a check valve and allowed the pressure to force all the cold water back into the city water main and made our neighbors water funky.

Note: new meters have check valves and wont allow this type of pressure release happen. The lesson learned, check your heater, make sure the valve works or get a point of use heater and get a new set of problems.

O ya, I almost forgot, my bed, it was directly above the tank.

Sorry for the lengthy post but to be honest this is the SHORT version. You might want to perform the necessary maintenance on this often neglected device.

Awesome shot guys, Very fun. Bigr, I don't think a rusted bottom would create a bigger explosion. Mainly because if the bottom is rusted, it will exploded at a lower pressure because the bottom is weaken. Using a new water heater can most likely hold a higher pressure before the bottom collapses making a bigger explosion. I love the slowmo btw.

i noticed that there was no foam insulation in the roof, i doubt it would actually matter with an explosion that size but they were testing an average house. if i were to try to improve this i would have a 2 story house and have the water heater in a basement of some kind, which would mean it would have a lot more resistance of actually getting out of the house.

I just caught the end of the show....I absolutely loved the water heater rocket. Great shot!

It's kind of scary for me though as I had an incident a couple of weeks ago.

We had an expansion tank blow on a secondary water heater in my house. My room in the basement is heated by tubing run through the concrete floor. This tubing is hooked up to a second smaller water heater separate from the main water system (it has a link but the valves are turned off unless we need to add water). Now my dad decided to turn on the water heater and get the system going since it's starting to get a bit cold here in Chicago. He turned up the water heater, then proceeded to add some water. 2 hours later I hear a large boom in the utility room. Turns out the expansion tank sitting on top of the water heater exploded because of the increased pressure. Yeah...the system didn't need any additional water...so when my dad added it plus turned on the water heater...the water warmed up...expanded...and boom!

The relief valves were still intact as the pressure wasn't high enough to trigger them...the expansion tank was a cheap one that was just crimped together in the center, so when the bladder inside expanded the top just popped off. We replaced it with a welded one so next time I hope the relief valves work properly, otherwise we may be duplicating the myth.

Funny thing is...my dad is the last person you would expect to make that mistake...he is an HVAC Expert...he deals with thermodynamics and hydrodynamics ALL the time in his job. He has a degree in Chemical Engineering. He just had a lot on his mind and wasn't thinking a lot about it.

Ok who is volontiering their full 2 story house with a basment out in the country? Also I would like to see them test water heaters that have glass cores in them. The ones they did had metal. If you noticed the old clip of a water heater they had, wich was solid metal. I belive them would be nice to test on the revist. They are far more ridged than new ones. They had to be no safty stuff back then. We had one as a mail box holder, a man drunk in an old buick faild to take it out. Only denting the old heater and totaling his car. In a house built to code… wouldn’t they have pvc piping in the building? Doesn’t pvc rupture around 180psi at 70*f? Thus realiving the presure before tank would rocket off to the moon?
Also test to see if a gas water heater reacts the same as the electric heater did. They have different methods to introduce heat into the water.

edit: Eric...their testing of the myth would be spot on in my case.

The system that exploded on us includes the following:

-45 Gallon Water Heater (currently in good condition)
-Copper Piping with soldered joints, limited Brass Piping with teflon taped screw joints.
-Several Heavy Duty Brass Valves (including one connected to a cold water line from the main water system)(the only one that really makes a difference is the one connected to the main water system, the rest are internal to the closed system)
-2 heavy duty brass faucets
-1 Pressure Relief Valve
-1 Pump
-1 Pressure Tank (two halves joined at the middle with a weld) (this is what exploded on us)
-1 Air Bleed Valve
-1 Pressure Gauge (up to 60 psi)

When functioning it is a a closed system maintained at about 35 psi when the pump is on, about 20 psi with the pump off.

Here's a diagram of the system:
http://img211.imageshack.us/my.php?image=underfloorheatingsystemsd4.jpg

Now I don't believe that this system could ever reach a point where the myth might happen...I just feel there are too many points of failure. I do believe that some of those points of failure could be removed without changing the functioning of the system though. The two faucets could be removed as well as the air bleed valve. Of course the internal ball valves could be removed also leaving only the gauge (which would be replaced by the gauge used in the show), pump, external valve for cold water supply (needed for separation from the other system), pressure tank, the copper/brass piping, and the water heater itself. If a system like that were under ideal conditions I believe it would still act the same way as the final two water heater rockets.

I'm a little bit surprised that the science behind the water heater wasn't covered. It actually doesn't have much to do with pressure. As a steamfitter we are taught much about steam. Everybody knows that water boils at 214 degrees at sea level. However water that is put under pressure boils at a higher temperature, conversely, water put under a vacuum boils at a lower temperature (which is why cooking in Denver takes different instructions). City water is around 60psi and I can't find my steamfitter instruction manual but the boiling point of water at 60psi is well over 300 degrees fahrenheit. If you take out the pressure relief valve and put a pipe plug in it and cause the heating element to malfunction so it never shuts off, you too can watch your house explode (don't really try this). If they had wanted a bigger explosion, just put more water in the water heater, because 1 cubic foot of water when turned to steam becomes 1200 cubic feet. Sooooo.......when the water is heated to over 300 degrees and then pressure reaches the bursting pressure of the water heater and the water heater opens up and is released to atmospheric pressure, all that water instantly flashes to steam creating a violent explosion. People have been killed by their water heaters exploding. This expansion of steam is also why an overheating car should never have it's radiator cap removed, the radiator cap keeps the coolant under pressure so that it boils at a higher temperature. Otherwise our cars would overheat all the time. But it's also why you should never remove the cap, because if the coolant is over 214 degrees, your going to get a lot of steam fast. Interestingly, these principles are also why bacon sizzles, the tiny droplets of water are flashing to steam! Cheers all, and everyone please check your water heaters to make sure that somebody didn't replace a leaking pressure relief valve with a pipe plug, it's probably the most common reason for exploding water heaters. Right on , later

Little more about steam. Some of the fast frigates the navy uses have large steam systems. Steam that is superheated (heated beyond it's boiling point) cannot be seen when theres a leak, you can hear it, but you can't see it. Interestingly, when there's a leak they used to (maybe they still do it this way) take a broom handle and wave it in front of them. When they would find the leak the broom handle would be cut off. In the past there were navy personnel cut in half by steam leaks. Steam is an extemely powerful force and can be very deadly when not respected

quote:

Originally posted by gearby:
I'm a little bit surprised that the science behind the water heater wasn't covered. It actually doesn't have much to do with pressure. As a steamfitter we are taught much about steam. Everybody knows that water boils at 214 degrees at sea level. However water that is put under pressure boils at a higher temperature, conversely, water put under a vacuum boils at a lower temperature (which is why cooking in Denver takes different instructions). City water is around 60psi and I can't find my steamfitter instruction manual but the boiling point of water at 60psi is well over 300 degrees fahrenheit. If you take out the pressure relief valve and put a pipe plug in it and cause the heating element to malfunction so it never shuts off, you too can watch your house explode (don't really try this). If they had wanted a bigger explosion, just put more water in the water heater, because 1 cubic foot of water when turned to steam becomes 1200 cubic feet. Sooooo.......when the water is heated to over 300 degrees and then pressure reaches the bursting pressure of the water heater and the water heater opens up and is released to atmospheric pressure, all that water instantly flashes to steam creating a violent explosion. People have been killed by their water heaters exploding. This expansion of steam is also why an overheating car should never have it's radiator cap removed, the radiator cap keeps the coolant under pressure so that it boils at a higher temperature. Otherwise our cars would overheat all the time. But it's also why you should never remove the cap, because if the coolant is over 214 degrees, your going to get a lot of steam fast. Interestingly, these principles are also why bacon sizzles, the tiny droplets of water are flashing to steam! Cheers all, and everyone please check your water heaters to make sure that somebody didn't replace a leaking pressure relief valve with a pipe plug, it's probably the most common reason for exploding water heaters. Right on , later

interesting...

by that reasoning I don't think it would matter what is connected to the water heater...the bulk of the hot water would remain in the water heater and once any portion of the system bursts that water would flash to steam...resulting in (I bet) a similar explosion.

I'd like to see a revisit on that...put the water heater in real world conditions but with the ideal conditions forced onto it (thermostat disabled, relief valve disabled)...let the entire system rise to bursting pressure and see what happens.

It's just a matter of whether or not you can bring the system above the boiling point without it failing prematurely. If you can then I would think it would flash to steam like you say.

A safe controlled way to test it would be to setup a system and have a controlled fail point in the system besides the water heater...say a remotely controlled faucet (or multiple faucets and increasing distances from the water heater). Let it come up to temperature throughout the system then make it fail and see if the water heater takes off. That kind of testing would most easily be done on a recycling water system such as an underfloor heating system like we have since it would bring the entire system up to temperature faster and easier.

interesting...

whatever happens I'd love to see a revisit...those were awesome shots of those water heaters going up.

I would think that a water heater connected to a city water system wouldn't get much above 60 psi. Unless you close the inlet valve the pressure should force the water and steam back into the city system. On a well system I believe there is a check valve for the pump. I would guess that exploding water heaters occur more often in houses with well water.

Also I would love to see a revisit, not because I think they are wrong but just as an excuse to blow up more water heaters.

My aunt was almost killed by an exploding hot water heater. She had just gone outside to hang laundry on the line. The trailer blew up behind her.

It was a natural gas leak in the closet where the water heater was installed. Gas leaks are a much more likely threat then water pressure explosions.
S-puppet

I was a little surprised that the tanks launched straight upward. That would seem to indicate that the bottoms blew out perfectly evenly around the entire circumference at the same instant, rather than one side. Almost like a cork popping instead of a seam ripping at the weakest point. Also, why did they blow at the bottom? Isn't it equally likely that the top would pop?

The water heater rocket was great. I know a guy who launched his hot water heater through the roof of his house, although under different circumstances.

The water lines had frozen in his house and he was working to thaw them when he came up with the idea of blowing the ice out of the lines using air. He was a scuba diver and had high pressure scuba tanks, so he adapted the tank to hook into his water pipes and turned the tank on. The air from the tank aparently went to the hot water heater due the lines being frozen and the hot water heater lauched through the roof of the house and landed in the front yard. Everyone around nicknamed his place "Little NASA" for quite some time after that.

quote:

Originally posted by rageear:
This is a strange question, but I was hoping someone might be able to answer it.

Does anyone recognize the t-shirt that Tory was wearing during the last jean myth? It was black and had a white icon of what appeared to be a gas mask.

I believe I have seen it before, but can't seem to find it with some Google'ing.

Any clues?

Thanks and great episode!

I noticed it too and I think it might be a sign that the video game company Pandemic has but im not sure,its a cool sign anyways.

The house water pressure can increase above the city water pressure.

All construction is required to have a back flow prevent on the water main to prevent any house water from getting back into the city main.

As they said on the show this is NO MYTH and this has occurred and people have been injured or killed when water heaters have exploded.

One item that I stress is to make sure and check the T&P valve at least once a year. Pull open the valve and drain some of the water out and make sure the valve closes again.

Part of the failure can be due to dirt, rust etc getting caught in the T&P and then it will not work as designed.

I wonder what it would take to contain that exploding water heater.. The forces excerted when that water heater blew was beyond belief

Would be fun to really build like a 200 gallon water-heater and let that explode

Gearby, I need to make one small correction to your posts: water boils at 212 degrees F. not 214. I'd just like to add that this is the classic effect of steam engines bl0wing up for more than 150 years; water heated under pressure so that it is all hotter than 212 Degrees will all instantly change phase into steam if the pressure is suddenly released and expand 1600 times. Thus the rocket effect. The MBs experiments precisely agreed with predictions including failing at 350 psi since that is their required design pressure. I suspect that the construction of modern tanks with the tops and bottoms welded on results in the bottoms bl0wing off since metal structures often fail next to weld lines.

This was the single most awesome thing I've seen on MB in a while.

I'd love to see them revisit this one only this time get a house scheduled for demolition and do it to the home water-heater and blow it out of a real, full, home!

quote:

Originally posted by dickfez:
Gearby, I need to make one small correction to your posts: water boils at 212 degrees F. not 214. I'd just like to add that this is the classic effect of steam engines bl0wing up for more than 150 years; water heated under pressure so that it is all hotter than 212 Degrees will all instantly change phase into steam if the pressure is suddenly released and expand 1600 times. Thus the rocket effect. The MBs experiments precisely agreed with predictions including failing at 350 psi since that is their required design pressure. I suspect that the construction of modern tanks with the tops and bottoms welded on results in the bottoms bl0wing off since metal structures often fail next to weld lines.

Yes, my bad, 212 degrees at sea level, at our union hall they said that steam expands between 1200 and 1300 times, whichever number is right anywhere between 1200 and 1600 is a heck uva lot and I wouldn't want to be near it when it goes. I'm not a plumber and don't work with waterheaters but in the videos they showed us, they looked like they were made in the '60s, the water heaters went up exactly the same way, with the bottoms blowing out, so that must be the weak point in the heater. I'd love to see a thick walled steel water heater maybe a couple hundred gallons go up, that would be spectacular.