Ive heard people say water heater tanks that have blockage or suddenly let cold water into hot tanks will"flash" and explode, causing severe, if not total structural damage -
Has anyone ever seen this firsthand?

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Originally Posted by dayslug24

Ive heard people say water heater tanks that have blockage or suddenly let cold water into hot tanks will"flash" and explode, causing severe, if not total structural damage -
has anyone ever seen this firsthand?

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I've seen a number of hot water tank incidents, but none that were a result of a sudden infusion of cold water.

As for blockages, the result of this type of scenario is that the T&P valve will pop-off.

Although I have seen instances where the T&P failed to pop-off -- In one instance the welded female orifice in the top of the tank blew up a 2-1/2" oak stair tread and turned the basement into a swimming pool -- In the other instance the pressure bulged out the side of an older hot water tank and blew apart the braided supply, turning yet another basement into a swimming pool.

We had an incident in Burien a few years ago where a hot water tank literally exploded from a build up of pressure, but that was because some idiot replaced the T&P valve with a plug.

I saw the results of a water heater that exploded some 55 years ago up in Wisconsin. It went up like a skyrocket. Blew through the first story and out the roof. It lit in a vacant field a half a block away and was flat as a pancake when it did.