billtex wrote:
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Wondering if the loud bang and frequent (hourly?) cycling of water heater = burst tank.
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I don't buy it. Sure, a closed tank could be overheated to the point of bursting. However, this is not a closed tank. Rather it is an open tank attached to a closed system. So any excess pressure in the tank would also put pressure on every water fitting and check valve in the system. I have got to believe a water line, fitting, or sink faucet would be a weaker point of failure than the hot water tank itself.
My bet is on a propane build-up that ignited. Look up 'propane cannon' on Google. I remember picking berries as a kid and hearing those go off to scare the birds. Sounded just like a shotgun, but was actually a propane charge popping off.
Just my $.02!
-Eric