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Old 03-13-2010, 07:47 PM   #1
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Water in conduit MYSTERY

Hi all,

For quite some time I've been noticing what appeared to be water marks around a switch box on a second floor interior hallway wall. At first they were fairly light, so much so I thought it might just be some strange drywall discoloring. Lately it has gotten much worse and I originally thought it might be some leakage from the attic fan on the roof but after going into the attic to investigate, there was no leakage coming from the roof. That was a week ago.

By chance, I happened to be installing a whole house fan this weekend and had to move the electrical in the attic so I had to cut into some conduit to relocate the wiring. When I cut into one of the conduits going to that switch box, I saw black/rust water come out onto the floor of the attic. The inside was all wet.

One end of this conduit terminates at that switch box and the other end at the opposite wall in an outlet. That wall has the garage on the other end.

I took out a 5-6 foot section between the wet part where the conduit turns to go down into the interior hall wall and the part that goes to the other wall. I didn't see any signs of water at the other end I cut closer to the other wall. This seems to be collecting toward the inside wall end.

That piece conduit has no openings or unions near that wall. The closest union was on the other end where I didn't see any water.

Does anyone have any ideas on how this is happening?

I'm including pictures for anyone willing to make a guess. I see a big rust spot on the floor of the box under the second to the right however, the conduit on the far left is the one with the water - you can even see water sitting on the wire nut (pictured).

By the way, there is no evidence of leakage from the roof anywhere. The water just seems to magically appear in that part of the conduit. What gives??

Water Spots:

Water in conduit:

Showing proximity to wall entry:

This is the other end closer to the other wall about 5 feet away from the water. This is the closest opening in the conduit until it gets to the switch box in the wall. If water was seeping in at this point I would think I would see some evidence here:

Here's a wide shot showing both ends:

The opened wall:

Water in the nut on the far left:


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Old 03-13-2010, 07:55 PM   #2
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It's called condensation.

What you have here is a cold area (attic) and a warm area (living space) with a continuous metal conduit running between them.

Warm, moist air is entering the conduit inside of your switch box, and then rises up to the cold attic where it condenses out as water. This water then drips back down the conduit, and settles in the junction box, fills up wirenuts, etc.

The cure here would be to clean out the ends of those conduits as best you can, and then seal them up with putty, caulk, or expanding spray foam. This will prevent the air flow and heat exchange from occurring -- and as a result -- the collection of moisture and water in your box.



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Old 03-13-2010, 09:23 PM   #3
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Originally Posted by kbsparky View Post

The cure here would be to clean out the ends of those conduits as best you can, and then seal them up with putty, caulk, or expanding spray foam. This will prevent the air flow and heat exchange from occurring -- and as a result -- the collection of moisture and water in your box.
and on top of this, it is required by code to seal a conduit that runs from different temperature areas just so as to prevent this.

I use duct seal. It is removable if needed and prevents the airflow that causes the problem you are experiencing.
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Old 03-13-2010, 10:45 PM   #4
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Both guys hit the nail.,,

C'est a condestaion and how thick the attic insluationg is on now and it should cover the conduits good otherwise get a duct seal to prevent air flowage that what happing with the conduit with diffince on tempture there.

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Old 03-14-2010, 08:17 AM   #5
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You will want to dry out the full length of the inside of that conduit before sealing it up. You'll have to rig up someting, for example let as much loose water drip out first and connect up a vacuum cleaner hose using duct tape. (Specifically a vacuum cleaner connection must have some air leaking in from the side as well to avoid overload. As it is uncertain how long it will take, you will have to err way on the long side (sev3eral hours). Feel at the other end of the conduit to be sure that air is flowing through.
The good conscientious technician or serviceperson will carry extra oils and lubricants in case the new pump did not come with oil or the oil was accidentally spilled, so the service call can be completed without an extra visit.
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conduit , water

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