I been working on water heaters for a lot of years but only as a sorta secondary thing. Recently an absolute certainty of whether a tank was leaking or if it was condensation dripping needed to be made. I know that it is very common for condensation to build up and drip onto the burner. And I know that sometimes it can be bad enough to put out the flame of the burner and or pilot. I also know that the position of the flue baffle can make a difference as to where the water drips. I've read that the burning process of natural gas has a moisture by-product that along with a cold portion of a tank can cause condensation and can add to the natural condensing of moisture from the combustion air in the flue.
Sometimes a leak is obvious - IE: Leaks on or off. Sometimes condensation is obvious - IE: Drips for awhile when a lot of cold water is in the tank, tapers off as the water heats up and eventually stops all together.
In the case I witnessed the dripping from was from between the portion of the flue pipe that protrudes below the tank bottom and the tank it's self in the combustion chamber. In my experience dripping from the inside of the flue pipe is condensation.
It is my theory that a fracture / hairline crack can retain water until heated up then expand and allow noticeable leakage. The Whirpool agent disagreed. ( It was an extended warranty job ).
Can anybody add their experience?