Originally Posted by LuciferMutt
My gas water heater is on borrowed time. Banging noises every night and the thing is 17 years old. Gonna replace it pretty soon! In my experience though, you can have one make the banging/rumbling noise for YEARS before they give out. This one's only been makin' noise for a year now.
The banging noise is the water in the bottom of the heater boiling due to the sediment floating around. It's your tank telling you it needs a flush.
Another tip is to remove the plastic drain valve and install a metal one before installing the new tank. It makes draining it much easier. The plastic ones fail and leak quite often.