Smoke stain on water heater

I’m calling this out all day long to have a plumber examine, but for my own curiosity why would there be smoke/soot stain above TPR valve on water heater. Its a gas fire unit and no other signs of anything wrong. No staining on floor from leaks.

Need to perform a combustion test on the unit, it may be running too rich. What did the flame look like do you have a pic of it?

It was a sealed unit and I couldn’t get the panel off as the the homeowners car was right next to it preventing much inspection.

Do you have a pic of the whole unit, what type of WH was this, exactly?

I dind’t take a pic of the whole thing however here is tag from the WH

That TPR valve also looks like it is too close to wall and unit may have to be repositioned.

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Had this issue once, and Charles Buell had a great explanation:

“The valve is hot, hot air moves upward carrying dirt in the air stream where it then deposits said dirt on the side of the tank. Source of dirt can be many.”


It’s just a theory. I don’t walk around wearing a tin foil hat on my head so what do I know?

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I call those ghost stains…I’ve seen them on electric water heaters and sheetrock walls. I believe differences in temperature, insulation causes it. Interesting phenomenon.


I concur, Ray. Ghosting. The soot particulate, smudging above the TPR valve is caused by the convective heat plume off.

If this was an electric water heater I would comment, suspect wiring conditions creating soot caused by the convective heat plume off.

The insulation captures atmospheric particulate from A: the indoor surface atmosphere at floor level and B: soot from burning NG, a fossil fuel energy and slows down convective heat plume off to escape at the largest opening at the water heater vesil case/cabinet.
Sorry for the edit members.

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Saw the same thing yesterday on an electric water heater. I noted it and recommended that the smudge be cleaned off and then to monitor for a return of the smudge. Should I have called it out as a safety concern or a need for as plumber to inspect further?

While we’re talking about ghost stains…I’d thought I’d share this one I saw yesterday…some ghosts are easier to see than others I guess…

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Further evaluation by a; ‘Licensed plumbing contractor.’ Could be poor drafting, inefficient combustion or more.
Best to protect your backside from litigation.

I would have preformed several equipment tests myself.

Ghostbuster - Ray Thornburg. He ain’t afraid of no ghosts!

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Electric heaters don’t have a drafting or combustion issue do they? Maybe I need to research this one a bit more!

Short circuits/circuiting in wiring create smoke/soot particulate from the jacket or other combustible materials, smudging appears above the TPR valve through the cabinet opening caused by the convective heat plume off.
Hope that helps.

That makes sense thanks for the clarification