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Old 12-19-2017, 04:16 PM   #1
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Sweating gas pipe on inside wall (anyway to stop it?)


Hello,

I'm currently having some annoying issues with my NG pipe sweating into a downstairs basement bedroom. It seems to only sweat once the temperature gets to about -7c (<20 degrees Fahrenheit). This became rusted enough that the inside joint eventually started leaking NG (small pin-hole leak) and I immediately called a plumber to replace the pipe and elbows.

I figured that since I was gutting the room anyway, I would pull the ceiling and drywall space around the pipe so that I could access the insulation where the pipe was sweating and make sure it wasn't all moldy and nasty and fortunately it wasn't as bad as I though it would be..

I did the following in order to put it all back together;
-Patched up the cracked concrete around the new pipe on 'both sides' of the wall and made sure it was sealed properly.
-I wrapped the inside of the pipe with some old insulation tape that i had and then replaced the old insulation with new ROKSUL exterior wall insulation, making sure to not fit it to tight.
-I also put insulation around the 4' of gas pipe inside the ceiling and wrapped it with vapour barrier to aid in insulating (don't think it was necessary as it never did sweat up there..).
-Finally, I re-sealed the vapour barrier with tuck tape, along with the upper elbow and it all seemed good.... UNTIL the temperature dropped to -7c and the sweating started again.

Not sure what to do now, especially since I have the drywall up, but I did leave some access due to building code and 'just in case' it started to sweat again. Although I would rather not have to open up the drywall again, I having no problem doing so if required.

Possible fixes?
Since I have enough access at the moment, would it be OK to put two small holes through the vapour barrier, fill all around the wall and pipe with expanding foam and then seal it back up (and of course, sealing the two holes in the VP as well)? I was thinking that sealing with expanding foam between the concrete wall and between the insulation and the gas pipe right up to the vapour barrier might aid in preventing the pipe from sweating 'inside' the wall.

Is there anything I can put around the 2 Pipe elbows and the length of pipe between them in order to keep it from sweating and subsequently rusting out again, while at the same time still staying within code?

I plan on putting a removable decorative box / covering over the top of the drywall (not completely airtight) so that it hides the ugly pipe and elbow.

Thanks for your help,
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Sweating gas pipe on inside wall (anyway to stop it?)-img_6694.jpg   Sweating gas pipe on inside wall (anyway to stop it?)-img_6711.jpg   Sweating gas pipe on inside wall (anyway to stop it?)-img_20171203_232739255.jpg   Sweating gas pipe on inside wall (anyway to stop it?)-img_20171204_134756898.jpg  
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Old 12-19-2017, 04:28 PM   #2
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Re: Sweating gas pipe on inside wall (anyway to stop it?)


The only reason it sweats is warm moist air from the house is condensing on it, So once it is sealed in a wall or ceiling the moisture is no longer a problem. Originally it could have been painted like the pipe outside to prevent rust.
Pay attention to how much moisture you have in the basement and solve that problem.
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Old 12-19-2017, 04:50 PM   #3
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Re: Sweating gas pipe on inside wall (anyway to stop it?)


Here are a few more photos...
(before..)
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Sweating gas pipe on inside wall (anyway to stop it?)-img_20171208_135209977.jpg   Sweating gas pipe on inside wall (anyway to stop it?)-img_20171208_135223162.jpg   Sweating gas pipe on inside wall (anyway to stop it?)-img_20171211_171733095.jpg  
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Old 12-19-2017, 05:12 PM   #4
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Re: Sweating gas pipe on inside wall (anyway to stop it?)


Clean the exposed pipe with a solvent and paint it with a metal paint. With a few 2x4s just box it out so you can drywall and tape it.
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Old 12-19-2017, 05:37 PM   #5
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Re: Sweating gas pipe on inside wall (anyway to stop it?)


The same rule applies to this pipe as it would to preventing a water pipe from freezing, insulate between the pipe and the cold but keep the pipe exposed to the heat. I couldn't follow all of your description, but wrapping the pipe in some areas may be helping it stay cold and a cold pipe is the other half of the condensation issue.

As for keeping the pipe warm I assume it is coming from underground. If all of the exposed pipe on the outside were protected from the cold air that might help, but codes might limit that, not my field.

Another aspect of foundation walls is they are in a pressure zone where air is flowing into the house. Any leaks would provide a path for that cold air.

Bud
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Old 12-19-2017, 05:46 PM   #6
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Re: Sweating gas pipe on inside wall (anyway to stop it?)


After Photos...
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Sweating gas pipe on inside wall (anyway to stop it?)-img_20171211_225114464.jpg   Sweating gas pipe on inside wall (anyway to stop it?)-img_20171211_225121796.jpg   Sweating gas pipe on inside wall (anyway to stop it?)-img_20171211_225139104.jpg   Sweating gas pipe on inside wall (anyway to stop it?)-img_20171219_163435628_hdr.jpg   Sweating gas pipe on inside wall (anyway to stop it?)-img_20171219_163421007.jpg  

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Old 12-19-2017, 07:17 PM   #7
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Re: Sweating gas pipe on inside wall (anyway to stop it?)


Quote:
Originally Posted by Nealtw View Post
The only reason it sweats is warm moist air from the house is condensing on it, So once it is sealed in a wall or ceiling the moisture is no longer a problem. Originally it could have been painted like the pipe outside to prevent rust.
Pay attention to how much moisture you have in the basement and solve that problem.
Yeah, it's REALLY dry here, but I think that room is fairly air tight and I believe a good amount of the moisture that I do get is staying in that room. I'll have to look into it to see how much humidity is in there.


Quote:
Originally Posted by Nealtw View Post
Clean the exposed pipe with a solvent and paint it with a metal paint. With a few 2x4s just box it out so you can drywall and tape it.
I'll clean it up well and paint over it. I did in fact pick up some heavy duty 'bed liner' spray from a Auto Body store (amazing stuff) and was thinking this might be the way to go in terms of helping to keep the pipe from surface rust, etc. I used a similar product on a older Dodge Durango hitch that was rusting and it still looks like I pretty much just painted it...(that stuff amazes me). I was thinking about adding some of that black foam insulation with the slit down the length or perhaps some smaller diameter plastic wrapped round pipe insulation (similar to that on a fresh air intake).

Quote:
Originally Posted by Bud9051 View Post
The same rule applies to this pipe as it would to preventing a water pipe from freezing, insulate between the pipe and the cold but keep the pipe exposed to the heat. I couldn't follow all of your description, but wrapping the pipe in some areas may be helping it stay cold and a cold pipe is the other half of the condensation issue.

As for keeping the pipe warm I assume it is coming from underground. If all of the exposed pipe on the outside were protected from the cold air that might help, but codes might limit that, not my field.

Another aspect of foundation walls is they are in a pressure zone where air is flowing into the house. Any leaks would provide a path for that cold air.

Bud
As in the photo above, the gas line comes in from the outside wall directly beside the meter and unfortunately there is no way to keep it insulated from the outside weather. I do think that part of the problem is that it is a very cold pipe and that adds to the issue. The pipe in the ceiling is cool to the touch but not cold, but the entire pipe (and elbows) from the inside wall to the ceiling seems to be much colder.
As for leaks in the foundation, it doesn't get wet enough here to notice and I've never had any 'wet issues', but having said that, this corner of the house always seems to be fairly cool when compared to the rest of the home so it may indeed be complicated by a foundation issue.
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Old 12-19-2017, 07:20 PM   #8
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Re: Sweating gas pipe on inside wall (anyway to stop it?)


I would box it in.
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Old 12-19-2017, 07:30 PM   #9
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Re: Sweating gas pipe on inside wall (anyway to stop it?)


To raise the pipe above dew point temperature cable heat trace the pipe and insulate it.
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Old 12-19-2017, 07:30 PM   #10
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Re: Sweating gas pipe on inside wall (anyway to stop it?)


The foundation leaks I was referring to are where the house rests on the foundation or any penetrations like the pipe you sealed. Also, the rim joist will have joints and is not glued to the sheathing. When I pressure test and inspect with an infrared camera the home owners often gasp. But any air leaks down there will be sending that cold air into the ceiling cavity keeping those pipes cold. It is a catch 22 because that outside air will also be dry. Have fun

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