Condensation on pipe.

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Old 02-09-14, 06:08 PM
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Condensation on pipe.

Hello everyone!

I'm remodeling my basement and I ran into a little problem, that hopefully someone can give me an easy fix!
I'll try and give all the information I can give for everyone to understand what is happening, here goes!

When I was tearing out the wall in the basement, I found my 1"1/2 PVC pipe that comes from the sink to a T- fitting, out of the T fitting straight up to the roof, then reduces to a 2" pipe to the septic tank the other direction.

Ok, were the pipe comes from the roof, inside the house, through the kitchen, into the basement, to the T- fitting, I have some condensation, several water bubbles on the bottom of the fitting, like on a glass of water on a hot day!
I'm assuming cold air is traveling down that vent pipe and meeting up with warm water from my sink/dishwasher at the T-fitting and creating condensation!
Is there anyway to fix this problem, because I'm going to put up a wall to cover all the pipes and I don't want mold accumulating behind the wall!

I have a picture of the condensation fitting uploaded!

Thanks for reading!
 
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Old 02-09-14, 07:28 PM
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Cold air obviously has something to do with it, but the warm water inside the pipe probably does not. Cold air would cause water to condense anywhere on the outside of the pipe if the dewpoint in your basement is that high. I suppose if there is hot pipe right next to cold pipe, the dewpoint on the surfaces of the pipe would vary dramatically within close proximity of one another. But IMO, it probably has more to do with the humidity level in the basement than anything. In reality, that pipe should be sweating all the way up through the walls until it reaches the attic. But it's probably not, since the vapor barrier behind your drywall and the insulation in the walls probably combine to prevent the dewpoint from crossing the temperature of the pipe. In the basement, though, it's exposed to warm moist air, its uninsulated and there is no vapor barrier keeping moisture away from it.

Hopefully the pipe penetrations are air sealed where the pipe passes through the framing. If not, close any gaps with spray foam. IMO, once the pipe is enclosed in an insulated wall it will be the end of the problem. But I would also question whether that pipe is fully insulated between the basement and the attic.
 
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Old 02-09-14, 08:06 PM
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I read what you posted and went and looked at the problem again.
I could see about 12" in. up the pipe from the T-fitting before it penetrates the floor to the kitchen, which I can't see until I go outside and look at the roof at the end of the pipe!

At the T-fitting in the basement is the only thing that is sweating and the 12"in. above the T-fitting isn't, so I'm assuming all I need to do is insulate all the pipe below the kitchen, then I can build my wall with insulation? Or would I be ok if I just built the insulated wall and then the pipes won't condensate?
 
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Old 02-10-14, 02:33 PM
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I asked 3 plummers and they gave 3 different answers, did I find a anonymous answer!
 
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Old 02-11-14, 11:39 AM
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Since the plumbers cannot give you logical answers, I'll pose questions have popped in my head, but have no logical reason to be there.

Can you feel if the fitting a different temperature from the pipes?
Is the condensation only on the fitting?
Does this get better/worse/same if the water is draining through it?
Does it get better/worse with hot vs. cold water running through it?
The shape of the fitting looks to me (in no way would I be called a plumber) that there is standing water in it. Can you tell if that's the case?

Note: I have no idea what any answer to any of those questions would mean. My uneducated guess is that the fitting causes standing water that allows the fitting to hold onto heat longer than the rest of the pipes. That allows condensation to happen. Some insulation around it could make it stop (but be sure of that before wrapping it up and hiding it behind a wall).
 

Last edited by Michael Rivers; 02-11-14 at 12:09 PM.
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Old 02-11-14, 12:07 PM
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Gosh, if 3 plumbers don't even agree, that would be scary. Then again, there could well possibly be different methods to correcting something.

In any case, I'd be weary of you insulating anything, without the certainty that it will stop, then you could quickly have a much bigger problem on your hands. I'm no expert of course, I'm just being as cautions as I would be, if it were my house.

Yikes, good luck... I will stick by to read up on the outcome... the knowledge just might help me down the road!
 
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Old 02-11-14, 12:11 PM
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I'd be weary of you insulating anything, without the certainty that is will stop, because then you will quickly get a much bigger problem on your hands...
Excellent point. I edited my earlier post to point out that insulation should be used only if that was proven to solve the problem.
 
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Old 02-11-14, 12:23 PM
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;P Great, and I just edited my post because I hate seeing my silly typo's! Big time OCD, I know. Oh well! 'ciao
 
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Old 02-12-14, 06:01 AM
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Hello all and thanks for your help, but I'll try and give my best answers to your questions!
When i tore down the wall to put new insulation and build a new wall, i noticed this drain pipe was condensating at the same fitting, but not the same spot, so i cut that fitting out and replaced it out with a new fitting, thinking it might stop.
When I had the pipe open ( no fitting ) I could feel cold air pushing out the pipe that
comes from the roof down to the basement to where I replaced the fitting!
I haven't noticed a difference of cold water or hot running through the pipe that makes it condensate, but ya never know!
The condensation is only at the fitting! Weird!
 
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Old 02-12-14, 06:11 AM
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Then there must be something different about the fitting.

Just thinking out loud;
Different material
Different thickness of material
Possibly standing water
The fact that it bends there and changes diameter might cause the cold air to transfer more thermal energy than elsewhere.
The FM* Principle.

That's all I can come up with.

*F-ing Magic.
 
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Old 02-12-14, 09:55 AM
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The thing with water is that is has to come from somewhere. It sounds like you've ruled out a leak (and it doesn't look like a leak anyway), so it has to be condensing from the air. Warm, moist interior air will condense on cold surfaces, which this pipe may be.

Insulating the pipe will help, but what's more important is to create a vapor barrier between the warm interior air and the cold surface. You can do this with some pipe-wrap insulation followed by plastic, or the closed-cell foam pipe wrap insulation (which both insulates and works as a vapor barrier).

Alternatively, when you close up the wall including insulation and a vapor barrier, the warm humid air won't be able to get to the pipe, thus eliminating condensation.


If you want some more ideas, take a picture of the whole wall from a few feet back. Maybe there's something around that you're not noticing - a heating vent, etc. that could be promoting condensation in that general location.

-Mike
 
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