Water Heater Rescue: Know-How, Troubleshooting, Anodes graphic

Lingo > Soot

The roof of a commercial water heater combustion chamber is black with soot

Soot defines itself. The reason it's included here is because it's sometimes and under certain conditions found in the combustion chambers and flues of water heaters -- and it's a bad sign.

If you didn't know that, you might not recognize it when you saw it -- or worry. One telltale is black stuff on the cover of a tank around the draft diverter, below right. Another is a blackened combustion chamber, as above right.

The reason to worry is that soot means a fouled combustion chamber and flues. Gas is not being completely burned. It's a downward spiral that can result in flames billowing out of the bottom of the tank, potentially setting anything nearby on fire.

Soot blown out of the flue accumulates on top of a water heater


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