MythBusters just did a water heater explosion. They did a great job I think. Here is a link to part that did not make it on the show Video - Discovery Channel Videos Online - News, Science, Space, History, Engineering just click expoding water heaters under the video window. Also their is a discusion on their forums. I think if some of you old timers can help set some of the posters on their forums straight it would be great. Many are saying that since the Mythbusters had all ports closed it will explode. But one in a normal plumbing system could never explode. I know that is false. I have seen many homes that where damaged due to water heaters that let loose with defective T & P valves. I just ran into a heater that was bulging. Thank god the home owner called me in time. here is the forums link Exploding Water Heater - Water Heater Rocket - Discuss It Here! - Topic Powered by eve community

Oh to keep this on topic the oldest water heater I came across was 1972 Rheem heater that had many boiler drain repair plugs in it.