Condensation Mystery!

Users who are viewing this thread

Shawn

New Member
Messages
5
Reaction score
0
Points
0
Location
Corpus Christi, TX
Here's the scoop and I'd appreciate your help!

Background: We have a 2 story house in S. Texas. Our home and A/C unit is 5 years old. We have Trane units w/a gas furnace. Our (2) units are inside our attic.

Intial problem: Our first floor ceiling I notice a stain and wet spot. It is the size of a dollar bill. The closest water source is our washing machine upstairs.

1st call for help: I call the plumber. He cuts a hole in the ceiling and find the horizontal drain pipe sweating or condensating. The drain pipe is cool. He then cuts a hole behind our washing machine. He says the washing machine and A/C drain are tied in together. He also goes into our attic to look at our units for anything unusual. He notes that everything looks fine and insulated where it needs to be. He then fills the drain, with water, to the top of the washing machine drain. He lets it sit and checks for leaks. No leaks.

2nd call for help: I call the HVAC. I have our units services twice a year. They blow out the drain and put bleach water during those times. My A/C guys checks out the regular stuff...clogs, temperatures at coil, water temp. Everything checks out.

Note: The A/C unit is approximately 20 feet away from the horizontal sweating pipe. Upstairs the vertical pipe before the sweating part, is completely dry.

This is our theory (tell me what you think). Some where after the point of the sweating drain....there is a clog that is slowing the draining process. Because the cold condensate, from the A/C, is allowed to stand a bit instead of flowing through like a normal drain....it begins to sweat due to the temperature differential.

Any ideas? Help me solve my mystery so I can fix the holes in my sheetrock.
 

Geniescience

Homeowner
Messages
2,137
Reaction score
4
Points
0
Location
humid summers hot, humid winters cold
insulate there too. Cold water in a metal pipe makes the pipe get cold. Same for plastic too, but slower to react.

Cold temperature makes condensation on the surface, because of high relative humidity in the air around the pipe. You know how condensation forms around a glass with ice in it? Same thing happens with cold water. Btw, does your toilet tank sweat? Do you have cold temperature ground water?

Why is cold water getting into that pipe in the first place?

David
 

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,770
Reaction score
1,190
Points
113
Location
New England
The thing that I would be more concerned with is to why there is enough moisture in the joist bay to allow it to condense in the first place? There should not be much of any air movement, and with the a/c on, the house (should be) sealed, there shouldn't be much moisture in there.

But, that being said, check the slope of the line to make sure there isn't a "belly" or dip which is holding the water, then, if you do, fix it, and insulate the pipes.
 

Verdeboy

In the Trades
Messages
2,041
Reaction score
6
Points
0
Have you turned off the A/C to really determine if it is the A/C condensate that is the problem?

There is so little A/C condensate, going through that large drain pipe that it is difficult to believe that it can cause the pipe to sweat so much.

Try using warmer water for your wash and rinse, and see if that gets rid of the condensation.

Also, if there was a clog, you'd have water backing up somewhere when you ran the washing machine.
 

Frenchie

Jack of all trades
Messages
1,239
Reaction score
0
Points
36
Location
Brooklyn, NY and Fire Island, NY
Insulate the pipe. I'm still tryin to understand why the 1st plumber didn't.

Also, what Jim said: there shouldn't be that much air getting into the space. Leaky house. I imagine your AC bill is higher than it ought to be...
 

Master Plumber Mark

Sensitivity trainer and plumber of mens souls
Messages
5,533
Reaction score
354
Points
83
Location
indianapolis indiana - land of the free, home of
Website
www.weilhammerplumbing.com
cleean out the drain

If you think that is what it is ,
simply clean out the drain line and see what happens.


but usually a laundry line has such a volume of wate r
passing through it that it never clogs up....

perhaps the cold drain line is going through a un-insulated
area of your house. something that never got sealed off good during construction.....heat from outside is getting into the joyst makeing the cold pipe condensate??


caluking on the outside of your house along the trim between the first floor and second could be someting to investigate.

I suppose this only happens in the summer time??
 

Shawn

New Member
Messages
5
Reaction score
0
Points
0
Location
Corpus Christi, TX
Here's a bit more info, that may help:

1) This horizontal drain pipe is PVC and about 20 feet away from the A/C. It in the 1st floor ceiling.

2) The washing machine is a front end loaded one which used a bit less water than the regular type.

3) These are the only things that are tied to this drain.

4) The home is on the coast of S. Texas and is very humid and hot. The A/C bills are pretty high this time of year. So there is a good amount of water that goes into the drain at this time of year.

Note: I wonder also, why it wouldn't back up, if it was a slow drain? Maybe because the washing machine used little water?

Hmmm. Shawn
 

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,770
Reaction score
1,190
Points
113
Location
New England
PVC will sag if not supported. As I said, have you checked to see if it runs at a constant slope and doesn't sag? Also, as several people have mentioned, inside the joist bay of an enclosed area, when you are running the a/c on a regular basis, there shouldn't be much air movement, and if well built, it should be as dry as the house if vapor barriers are intact. If it is leaky, and outside air gets into that space, then sure, it will condense, but it should be as dry as the house. Insulation around the pipe will likely raise the exterior temp above the dew point and would be the first line of defense.
 

Geniescience

Homeowner
Messages
2,137
Reaction score
4
Points
0
Location
humid summers hot, humid winters cold
is it in an unconditioned space? The pipe that is sweating, i.e. condensating moist air into surface water. Is that pipe at that location outside the area known as the building envelope, which defines the area where air is conditioned...

Shawn, your description repeats itself but doesn't add much.
-- The pipe is 20 feet away from your attic AC. I guess that means the pipe goes down one floor level, since it's in the first floor ceiling of a two storey house, and your AC is in the attic.

What I don't get is why COLD water is in it in the middle of summer in Texas. Maybe this is a real leak, not a cold temperature humid air condensation phenomenon situation.

David
 

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,770
Reaction score
1,190
Points
113
Location
New England
Ayup...the condensate comes off of the evaporator coils, so it better be cold! Still, to have moisture condense on the outside of the drain pipe 20' away, in a joist bay that has a drywall cap means that there must be some outside air getting in there. Insulate it, and monitor it.
 

Shawn

New Member
Messages
5
Reaction score
0
Points
0
Location
Corpus Christi, TX
Insulating away

Well, we are going to insulate the sucker today!

According to my plumber, the slope is fine.

Also, since I have the ceiling open and the pipe is exposed..it dries out during the day. At night, it is getting a little moisture around it. I am guessing that is because the A/C unit isn't running as much at night.

I'll let your know how the insulation is working. Shawn
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks