From watching stuff on telly, it seems that what we call an unvented cylinder with immersion heater is common in the US. Mythbusters did a bit on what happens if they explode...
They had to defeat all the safety features (thermostats, over pressure & over temp valves), but they managed it. The bottom seam failed and cylinder launched upwards, punching through a floor and roof of the skeleton house they'd put together
They had to defeat all the safety features (thermostats, over pressure & over temp valves), but they managed it. The bottom seam failed and cylinder launched upwards, punching through a floor and roof of the skeleton house they'd put together