Is it safe to drain my 40 gallon water heater, fill with a few gallons of white vinegar, and then let it sit overnight? It is 8 years old (2004 model), and every day I hear explosions in it (scale breaking up?).

I assume that this would help clean dissolve all of the sediment which doesn't seem to come out by draining the tank alone. Vinegar seems to work well for cleaning shower heads?