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I was doing some household cleanup in the storage room where my heat tank is located when I noticed a burn mark on the wall frame near the pipe that goes from the heat tank to the shower next room.

I'm of course not thinking that this is due to the hot water itself, so I can only believe that this happened during an electric short to the ground.

I have some questions about this:

  • How can I know if this is a recent burn mark or not?

  • Is this a sign that something is not grounded properly somewhere and that during a thunderstorm, similar burn mark may appear again?

  • How can I prevent that from happening again?

  • Should I call a plumber or an electrician?

Niall C.
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Pierre-Alain Vigeant
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2 Answers2

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I'd say it's a mark left by the plumber's torch while soldering the copper pipes rather than an electrical problem.

Danny T.
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  • +1, saw the same thing in my home when I bought it. So far, nothing has burned down, but it was a sign of poor construction. – BMitch Oct 03 '11 at 20:08
  • Yeah that is probably it. That remove the fear my wife and I had when we saw this. – Pierre-Alain Vigeant Oct 03 '11 at 20:53
  • 100% it was the plumber, being just a little sloppy. Some heat (even a wee bit of flame) blew around the pipe, thereby scorching the wood. –  Feb 15 '12 at 15:30
  • Saw similar after ripping out my bathroom ceiling. I originally thought maybe my (max)HOT water did it through the pipe. But after testing there's no way. It was 100% the torch from plumber repair before I bought the place. +1 – akahunahi Jun 02 '19 at 19:54
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What Danny said - someone didn't use a flame shield while soldering the pipe.

The soldering process involves blasting the copper pipe with a hot flame until the lead solder melts:

enter image description here

A RESPONSIBLE plumber will use a flame retardant barrier while soldering. Whoever did your pipes just chose not to and nearly burned down your house.

Sorry, so to answer your questions:

  • How can I know if this is a recent burn mark or not?

Water pipes don't get hot enough to scorch wood. If they got that hot, your hot water fixtures would have started venting steam.

*      Is this a sign that something is not grounded properly somewhere and that during a thunderstorm, similar burn mark may appear again?

No, it's a sign you had an idiot working on your house.

*      How can I prevent that from happening again?

Don't hire that idiot plumber again (assuming you hired him to begin with).

*      Should I call a plumber or an electrician?

No - and its just a surface scorch so your wood is ok too.

The Evil Greebo
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  • I did not hire any idiot plumber, or any plumber at all, we brought the house 4 months ago. I just noticed this burn mark. Now that I think about it, the previous owner must have been that idiot guy. I have found a bunch of place where there was soldering that shouldn't be there (like below the faucet in the bathroom). I can't even change the faucet without breaking the soldering, somehow. – Pierre-Alain Vigeant Oct 03 '11 at 19:06
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    Did this seriously risk burning down the house? No. As long as the plumber was there watching, it would not have done so. In fact, a quick spritz from a water bottle on any scorched area will put any problem quickly to rest. It takes a few seconds playing a flame on wood to send it up in flames, but only a second to create a scorch mark. Yes, it is best to do your work cleanly. Heat shields are always a good idea, but no professional plumber I've watched has used one, nor did they come even close to needing one. I'd bet this mark was left by a previous homeowner DIY attempt. –  Feb 15 '12 at 15:38