Andrew Taylor wrote:
Out gas fired hot water heater has started making loud popping noises
when the flame is on. It still seems to work fine otherwise. Does anyone
have experience with this. Is it anything to be concerned about? Thanks

It's just bubbles of hot water "exploding" into steam on the
bottom of the heater shell where the flame hits.
Occurs on heaters which have not been periodically drained/flushed
to prevent mineral buildup.

http://groups.google.com/
Do an Advanced search on this ng for " draining water heater" or
similar. Been discussed ad nauseum.

On an old heater, the minerals are solidified and won't drain out though.

Jim