Don't know if was any cause of the electric water heater missile. However, electric water heaters, for some reason tend to create hydrogen gas, moreso than other heaters. Yes, did actually read it from a reputable source. Don't know why, but I can only surmise that maybe it is some type of minute steam bubble reformation occuring at the heating elements. Gotta admit for those 2 elements, considering for heat recovery, to bring a 60 gallon tank up to x-number of degrees, they gotta get pretty hot. But with daily usage, the small amts of hydrogen gas get flushed out with use. I guess the problem occurs when those 60 gallons become continually heated with no relief. ie vacation or the snow birds heading to FL for their annual 4 month solistic. Guess that is the reason why in at least my owner's manual, they tell ya to shut-off supply and drain tank for an extended absence.