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Junior Member
Registered: 11-08-07
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The one thing that did surprise me was that the little water heater didn't fly into the wild blue yonder. Must have been because the fittings were too weak so they blew off instead of the bottom of the water heater? Maybe there wasn't enough water? Any thoughts on why this might be?
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Junior Member
Registered: 11-09-07
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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
Good job! Your the voice of reason here. The gas co. concurs in that its all about the boiling point of water UNDER PRESSURE, which by the way expands 1600 times. They detonate their experimental water heater explosions by creating a cold water "hammer" and throwing it into the super heated water in the tank suddenly. Cudos! |
Junior Member
Registered: 11-09-07
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I cant believe what i saw on tv. The exploding water heater episode was exactly what happened at my house a few years ago, almost killing 5 people. It was a saturday, march 8, 2003. I was doing laundry all day, and aroung 3pm i put my last load in, and left for the mall. when i was still in the driveway, the water heater exploided. it was old, and the pressure valve wasnt working. it went through the kitchen, master bedroom, out the roof and 250ft into the woods. The house was condemded within an hour, and we were out of our house for a year while they rebuilt. 80% damage to a 4,000 square foot home. All the windows were blown out, there were no more stairs on either floor. 5 people were in the house, and just happened to be in the 20% that was not totalled. The fire dept was stunned. My brothers friend was thrown from the house. If you dont believe me check for your self. It was on the news, in the paper, and the fire dept has record of it. It happened in Munson Township, Ohio 44026 on Butternut Rd.
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Senior Member
Registered: 11-04-07
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quote: Originally posted by jlg3280:
I cant believe what i saw on tv. The exploding water heater episode was exactly what happened at my house a few years ago, almost killing 5 people. It was a saturday, march 8, 2003. I was doing laundry all day, and aroung 3pm i put my last load in, and left for the mall. when i was still in the driveway, the water heater exploided. it was old, and the pressure valve wasnt working. it went through the kitchen, master bedroom, out the roof and 250ft into the woods. The house was condemded within an hour, and we were out of our house for a year while they rebuilt. 80% damage to a 4,000 square foot home. All the windows were blown out, there were no more stairs on either floor. 5 people were in the house, and just happened to be in the 20% that was not totalled. The fire dept was stunned. My brothers friend was thrown from the house. If you dont believe me check for your self. It was on the news, in the paper, and the fire dept has record of it. It happened in Munson Township, Ohio 44026 on Butternut Rd.
I certainly can believe it happened, after seing the same result both on the Mythbusters-episode and the result with the bigger tank on the Discovery-site.. |
Senior Member
Registered: 09-28-06
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Being as old as I am, I remember having water heaters that had NO safety devices whatever. Essentially, these had a gas burner that had to be lit by hand and shut off when the water was hot.
Other than that, just a big steel container. No insulation, either; you'd just put your hand on the tank to see how much hot water you had!
Ah, the 50s...
Everyone was always paranoid about these things. If you went out for even a short trip, it was always, "did you turn off the water heater?"
As I recall, they were equipped with a sort of blow-out plug which was supposed to go before the whole thing exploded, but then you'd come home to a flooded basement.
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Junior Member
Registered: 10-17-07
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I've been waiting for the new episodes for weeks like a kid counting down to Christmas and this episode was exactly what I was hoping for. That moment just before the final heater shoots into the air and Jamie is totally caught by surprise? Classic.
I never had an interest in science prior to this show. My father was totally floored when I knew what 'psi' stood for.
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Junior Member
Registered: 11-09-07
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Water utilities all over the country are installing backflow prevention devices in customer's services without telling them that they must install safety equipment to prevent their water heaters from exploding. The backflow valves seal off the customer's plumbing and thermal expansion can cause pressure to rise to dangerous levels. When you read about water heaters exploding, this is probably the cause. I took the backflow valve out of our meter.
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Junior Member
Registered: 11-09-07
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quote: Originally posted by Redhoss:
Water utilities all over the country are installing backflow prevention devices in customer's services without telling them that they must install safety equipment to prevent their water heaters from exploding. The backflow valves seal off the customer's plumbing and thermal expansion can cause pressure to rise to dangerous levels. When you read about water heaters exploding, this is probably the cause. I took the backflow valve out of our meter.
Water utilities are installing backflow devices at the meter or meter yokes. But they do inform the homeowners that a thermal expansion tank must be installed. If not every time the water heater cooks the water the T&P Valve will spit a little due to pressure build up. As an Illinois licensed plumber I have ran into this many times when a home owner replaces their water heater and removes the expansion tank. Now can a water heater blow up without a backflow device or even with an expansion tank? YES it can. Think about it a brand new water heater would be hard pressed to see one fail. Don’t get me wrong they do some times. But most water heater failures are on 10+ year old heaters. The welded joints on the tank are not as strong as the used to be. So the likely hood of the heater rupturing and letting loose super heated water which will flash to steam is very possible and has happened. Don’t you people read the first two posts in this thread? There are two people there showing you pictures and news articles showing the damage of a water heater exploding. I could go on with all the physics involved in how a water heater works and pressure vessels. But I would have to make at least a 10 page post just to cover the basics. Just learn one thing from this show. Test your T&P valve yearly. That is what the little lever on the end if it is for. If it’s dripping replace it. DO NOT EVER CAP IT. Also make sure there is a pipe attached to the valve that leads down to no less than 6 inches to the floor. This is in case it does work it won’t scald a child in the face or chest. If you have any questions feel free to contact me at my e-mail. RonH@A-Archer.comOh if anyone out there has a video that Rheem made I think it was back in the 70's of a water heater expoding. It was in a normal plumbing system. May even be older than that. If so please post a link here. I think it would help explain things a bit more. |
Junior Member
Registered: 06-11-07
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I remember the explosion in Burien, they were doing some plumbing work and someone had partially drained the hot water heater IIRC.
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Junior Member
Registered: 11-09-07
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I stand corrected, it was not Rheem that put out the video. It was Watts. It is called "Explosion - Danger Lurks! " here is a link to a preview I found Explosion - Danger lurks |
Junior Member
Registered: 11-10-07
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quote: Originally posted by SewerRatz:It was Watts. It is called "Explosion - Danger Lurks! " here is a link to a preview I found Explosion - Danger lurks
That was produced by Watts back in 1948. I have the video tape of the full version, but it is too large to put on You Tube. Water heaters exploding is no "myth", it is real and it happens 30-40 times a year across the country. If there was a way to post the entire video, it explains the science and reason for this danger. The danger is not "pressure", the danger is the "heat energy" stored in that pressurized water. When water is pressurized, the boiling point rises, thus pressurized water can be heated to a much greater temperature than water at atmospheric pressure. When heated pressurized water is released to atmospheric pressure, the boiling point drops to 212 degrees. The water may have been heated to over 400 degrees when pressurized and still not have reached its boiling point, but, when that water is released at atmospheric pressure, that water is instantaneously turned into steam - which is the explosive force creating the shock wave which blows structures apart. |
Junior Member
Registered: 09-05-07
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PSA - Public Service Announcement
If you guys are going to test your T&P valve, don’t do it on Friday night, Saturday or Sunday. Test the valve when the stores are open and you can get a replacement. Even if you can get a replacement, plumbing can be a messy and inexact science. If the treads have rotted to the point where you need the services of a plumber, it is always better to just pay him straight time rather than over time.
It was mentioned once, earlier, about a T&P valve failing closed. Most times they fail open (thankfully) most especially when you test them after they have remained untested for many years. An old plumber I knew said he’d take a ten dollar bet against a T&P valve failing (leaking) every time it was sitting there for ten, fifteen or more years unused and untested.
The stuff about the one way valve on the water meter causing the T&P valve to spit (no place for the expanding water to go - that is expansion below the boiling point) was covered on a recent episode of This Old House. They added an expansion tank to solve the problem.
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Junior Member
Registered: 07-12-07
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Junior Member
Registered: 11-09-07
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Back in October of this year I had gotten an e-mail with the following pictures attached. I called the home owner told her to get out of her home call the gas co. to turn the gas off to the house. I did not want her near that thing anymore. http://i7.photobucket.com/albums/y292/SewerRatz/Water%20Heater/IMG_1959.jpghttp://i7.photobucket.com/albums/y292/SewerRatz/Water%20Heater/IMG_1958.jpghttp://i7.photobucket.com/albums/y292/SewerRatz/Water%20Heater/IMG_1957.jpgThe T & P was frozen shut and the thermostat had failed. She heard a loud popping noise from the basement. She looked around and found the tank was bulging. There was no backflow device at the water service and no other ways of making it a closed system. This was a real danger of happening. There is another danger that can happen with water heaters which is just the opposite of what we are discussing here. More and more I am seeing water heaters on the first and second floors of homes. If for some reason if someone shuts off the water and drains down the plumbing system from a sink or such it can cause a vacuum in the tank and cause it to implode on itself like a crushed pop can. To prevent this, plumbers should install a vacuum relief valve on the cold side of the tank after the shut off valve. |
Junior Member
Registered: 11-10-07
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I would guess the botton tends to come out of the water heaters, especially older ones, due to the accumulation of rust and scale causing it to corrode more. A rupturing pressure vessel tends to un-zip at the seams, much like a rubber baloon pops. You do not tend to just get a hole you often get two or more pieces. The welded bottom may just be the weak point. it would have bee interesting if they had spent 10 second of the show on a little failure analysis.
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Junior Member
Registered: 12-01-03
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In Sept., we had an incident at our county fair, with a home-made air tank. The bottom half was buried in the ground, with a yard of concrete around it. Mounted on top, was a 20' pipe with a old factory steam whistle at the top. They had a construction site air compressor attached, by a hose, to pressurize the tank. Every night, they would blow the whistle to call people over for the night's cash drawing. Everything worked fine fro the first 3 nights. On the fourth night, they were pressurizing the tank and the bottom blew out. The tank launched out of the ground and went 25 or 39 feet into the air, before the hose stopped it. It blew a crater in the ground that was about 6 ft. across and 3 ft. deep. The concrete apron was blown into the air and fell back into the hole. One guy got a broken nose, another got a fractured bone in his ankle. Others got minor cuts and bruises. here are a couple of pics. http://i135.photobucket.com/albums/q122/olesniper/100_0221a.jpghttp://i135.photobucket.com/albums/q122/olesniper/100_0216a.jpghttp://i135.photobucket.com/albums/q122/olesniper/100_0223.jpg |
Junior Member
Registered: 11-09-07
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quote: Originally posted by JerryPeck: quote: Originally posted by SewerRatz:It was Watts. It is called "Explosion - Danger Lurks! " here is a link to a preview I found Explosion - Danger lurks
That was produced by Watts back in 1948. I have the video tape of the full version, but it is too large to put on You Tube. Water heaters exploding is no "myth", it is real and it happens 30-40 times a year across the country. If there was a way to post the entire video, it explains the science and reason for this danger. The danger is not "pressure", the danger is the "heat energy" stored in that pressurized water. When water is pressurized, the boiling point rises, thus pressurized water can be heated to a much greater temperature than water at atmospheric pressure. When heated pressurized water is released to atmospheric pressure, the boiling point drops to 212 degrees. The water may have been heated to over 400 degrees when pressurized and still not have reached its boiling point, but, when that water is released at atmospheric pressure, that water is instantaneously turned into steam - which is the explosive force creating the shock wave which blows structures apart.
Hi Jerry, thank you very much for your input. I went to Watts website and ordered the DVDs they have about scalding and water heaters blowing up. I come across so many stuck closed T&P valves it is scary. Thank the lucky stars that the thermostats and other safty devices where in working order. |
Junior Member
Registered: 03-24-07
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quote: Originally posted by eric1:
I see a problem with this myth. ........ I would like to see the test run again connected to some plumbing fixtures using several different types of pipe, to see if houshold plumbing would even hold up to that kind of pressure. ...... Eric in Tallahssee
you may be right, that the plumbing would fail long before the pressure reached 350psi, but this happened just a couple of weeks ago near where I live. In short, the tank exploded, and was launched into the air, landing 70 feet away from the house, and blew parts of the house 300ft away! |
Junior Member
Registered: 11-12-07
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I actually knew someone who was working on a hot-water heater at a country club in Goderich, Ontario who was killed by the hot-water-heater when it exploded...
I don't remember the details, but if anyone cares to I'm sure there's an article about it somewhere.
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Junior Member
Registered: 05-10-07
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If you ever revisit this heater, step it up a notch and try a boiler. I use two 15 HP high pressure boiles on a daily basis to produce steam. I am aware of their danger and maintain them carefully, but I would love to see what one of those would do if the safety controls failed.
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