Whirlpool Natural Gas water heater Model #: FG1F4034T3NOV

[pigsooie96]

I have two water heaters that ran fine for a couple of years. Then one day, when the "good" water heater (Hotpoint Model#: HG40t1A) would kick on, it would blow the Whirlpool water heater completely out.  And not just the pilot light.  The Whirlpool could be on "full burn" and when the Hotpoint would kick on, the whirlpool would blow out.

The heaters are set up side-by-side and run off of one gas line.  The gas line comes down and branches off to each heater.  The flues tie together and then go out of the house.  There is a separate hot and cold water line for each heater.  I have checked the flues and all is clear.  I lit a match over each one and the smoke from the match seemed to be getting sucked up fine over each heater.

Any suggestions as to what the problem might be?

Thanks-

 

[RegUS_PatOff]

I'm no expert, but I would think it's a partially blocked flue..

bird's nest, etc ..