Originally Posted By: Dean Call
This post was automatically imported from our archived forum.
Interesting how different materials are used in different parts of the country.
Has anyone ever seen a house blown up from a
steam explosion?
A steam explosion is more violent than gas.
I have, back in about 1965 in Shawnee Kansas, it raised the whole house off the foundation, blew out walls and turned the water heater into a rocket when the bottom finally blew out when each gallon of water instantly flashed into ( I believe it's 30,000 gallons) of superheated steam.
The homeowners had just bought the house and had moved in a just few items.
The wife was there cleaning and getting ready to move in when she flushed the toilet and noticed steam coming into it.
She called he husband at work and he said "I don't know what is causing it but you better get out of there".
About an hour or so later the water heater's bottom blew out, rocketing it up through floor joists and rafters edgewise, through the roof and down the street a couple of blocks where it landed in a ball field.
On it's way through, it passed through a cast iron lavatory, breaking it in little pieces.
I've often wondered why they didn't call someone to come and shut the gas off in time. 
I got to help my boss at the time and the fire chief spend a couple of days finding all the pieces of pipe and putting them back together to find what caused the explosion.
The conclusion of the investigation was that the gas valve was held open by the black flakes from the soft copper gas line and caused a run away water heater condition.
As the water became super heated way above it's boiling point, the plastic dip tube became soft like spaghetti and forced it's way up into the cold water inlet causing a solid plug and a closed vessel when the toilet had been flushed.
Although the water heater did have a safety valve, it was very old and it too was a solid plug from age and corrosion.
Being under pressure, naturally the water didn't turn into steam until and hour or so later when the bottom blew and lowered the pressure, causing 40 gallons of water to instantly flash into steam.
After that happened, my boss held several slide show seminars educating firemen, plumbers, the gas company and inspectors about what can happen when copper is use for gas.
Believe it or not we still have some DIY folks that continue to use copper for gas on water heaters occasionally.
When I remove one, I can bend the soft copper back and forth and dump out a hand full of black flakes.
Several years ago I turned down a copper gas line on a home inspection, then the homeowner called the city and the city guy told them there was nothing wrong with it so I had to prove it to them too.
We are still passing the word, I guess until they start using some other odor-ant that doesn't attack copper.
Guess I walked right into that 