What is causing this soot

[Frank Bombardiere]

This is a 4 year old sealed burner gas water heater. There was soot above the T&P valve. Never seen this before. There was no soot on the vent hood or top of the tank, only above the T&P valve. What caused it?

[Scott Patterson]

This is a 4 year old sealed burner gas water heater. There was soot above the T&P valve. Never seen this before. There was no soot on the vent hood or top of the tank, only above the T&P valve. What caused it?

From what I have learned, it is normally caused by dust, soot, etc in the air. I have seen it with electric water heaters as well as gas. The heat escaping around the TP valve creates a chimney effect and the debris in the air collect. That might not be the best description but I think it is pretty close...

[Frank Bombardiere]

From what I have learned, it is normally caused by dust, soot, etc in the air. I have seen it with electric hate heaters as well as gas. The heat escaping around the TP valve creates a chimney effect and the debris in the air collect. That might not be the best description but I think it is pretty close...

Sounds plausible. I have seen that on other heat producing things around the house. Guess it did not cross my mind that this could be the same thing. Thanks

[Bob Harper]

Be careful labeling this 'soot'. It is technically "black particulate matter" until you have a qualified lab report that identifies exactly what it is. Yes, often 'soot' from combustion of NG or LPG can spill outside of the combustion chamber, get captured by the outer jacket and filtering its way up where it exists out the TPR port. Or, it can be household particulates from any of several sources that plate out here.

I would simply note that a qualified technician should inspect the appliance and perform combustion analysis to ensure proper combustion and venting.