Condensation on Water Tank Exhaust Pipes

Reply

  #1  
Old 01-07-14, 10:20 AM
Member
Thread Starter
Join Date: Jul 2013
Location: Canada
Posts: 15
Received 0 Votes on 0 Posts
Condensation on Water Tank Exhaust Pipes

Hello,

A couple years ago we had a new hot water tank installed. The company had installed the tank in a different location and ran new exhaust piping over the ceiling of a room and through the foundation wall of the house.

On days such as today where it is very cold outside (appxox. -24C/-11F) condensation is building up on the piping inside the house [see attached pictures]. Water droplets are falling from the holes the installers cut through the ceiling when they were installing the pipe.

I have sensitive equipment in the room and water has already fallen on it. What is the best and most cost efficient way to prevent such condensation from building up and falling from these exhaust pipes?

Thank you
 
Attached Images      
Sponsored Links
  #2  
Old 01-07-14, 10:25 AM
Member
Join Date: Apr 2011
Location: nj
Posts: 576
Received 0 Votes on 0 Posts
You probably have a draft somewhere in that chaseway thats causing that? Maybe even high humidity, but i doubt that with these temperatures, unless your starting a rainforest in your basement. Is the condensate on the intake, exhaust or both?
 
  #3  
Old 01-07-14, 10:44 AM
Member
Thread Starter
Join Date: Jul 2013
Location: Canada
Posts: 15
Received 0 Votes on 0 Posts
I am not sure which one would be classified as the intake and exhaust. Another picture has been attached. There are actually only two pipes coming from the water heater, so the other two on the right side of the picture are probably going to the furnace.

Looking at the set of pipes on left, only the one circled in red appears to be forming condensation and it is cold to the touch. The pipe beside it (in that set) is hot to the touch and does not appear to have any condensation.

Looking at the set of pipes on the right, again only the one circled in red appears to be forming condensation.

The temperature of the room is around 19C/66.2F.
 
Attached Images  
  #4  
Old 01-07-14, 10:52 AM
Member
Join Date: Apr 2011
Location: nj
Posts: 576
Received 0 Votes on 0 Posts
With those cold lines forming condensate that would lead me to believe that there's high humidity in there. Is there condensation on the entire length of pipe or just one area?
 
  #5  
Old 01-07-14, 10:58 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 1 Vote on 1 Post
Drawing outside air for combustion will cause that pipe to be super cold this time of year. Even with relatively low humidity in the home it's likely that the outside temperature of the pvc pipe will be below the dewpoint in the building.

How to solve the problem?

Insulate the pipe the full length from where it enters the building to the appliance,

or use a dehumidifier to lower the relative humidity in the building and decrease the dew point below the temperature of the pipe.
 
  #6  
Old 01-07-14, 10:59 AM
Member
Thread Starter
Join Date: Jul 2013
Location: Canada
Posts: 15
Received 0 Votes on 0 Posts
It appears to be the entire length. At the back wall where it goes outside the house, at the centre point, and then if you follow the pipe outside the room (in the furnace room) there is also condensation on the pipe before it connects to the water heater.

Perhaps I will purchase a hygrometer to see what the humidity level is.
 
  #7  
Old 01-07-14, 11:01 AM
Member
Join Date: Apr 2011
Location: nj
Posts: 576
Received 0 Votes on 0 Posts
Great info troop. -11* air going through a pipe in a 65* room......

Do as troop stated. Purchase some duct wrap and zip ties at your nearest big box store and that will definitely solve your issue.
 
  #8  
Old 01-07-14, 11:02 AM
Member
Thread Starter
Join Date: Jul 2013
Location: Canada
Posts: 15
Received 0 Votes on 0 Posts
Would I need to tear down the ceiling to insulate the pipe?
 
  #9  
Old 01-07-14, 11:04 AM
Member
Join Date: Apr 2011
Location: nj
Posts: 576
Received 0 Votes on 0 Posts
To get at all of it, yes. OR you can purchase pipe insulation which would be a lot more money.
 
  #10  
Old 01-07-14, 11:44 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 1 Vote on 1 Post
I would think with that cold air coming in, even if the room were like 25% humidity once would still see some condensation.

I scratched my head a bit when looking at dew point charts a little while ago as to why none of the charts I found went down below 32 ... then it hit me... they don't call it 'dew' anymore at that point! It's FROST!

The fact that the hot exhaust is running right next to the intake is probably preventing that pipe from becoming a frost encaked popsicle.
 
  #11  
Old 01-07-14, 06:56 PM
Member
Thread Starter
Join Date: Jul 2013
Location: Canada
Posts: 15
Received 0 Votes on 0 Posts
I got the hygrometer and it reads 26-24% humidity with a room temperature of 19C/66.2F - 20C/68F.

The temperature of the cold pipe for the water heater mid way in the room is 14C/57.2F. Near the wall where it is about to exit outside the house it is roughly 6C/42.8F and there is frost and ice at that point [see attached picture]

Using the dew point calculator found here: Dew Point Calculator
It indicates that for a RH of 26% and a temperature of 20C/68F the dew point is 0C/32F. The frost and condensation at the end of the pipe makes sense in light of the above numbers. However at the midway point it doesn't seem cold enough for such large droplets to form (and fall down).

Though there is condensation, I am wondering if these larger droplets that were falling at the midpoint of the pipe this morning were a result of frost buildup at the end that was thawing and then sliding down the pipe.

Currently the outside temperature is -17C/1F and the larger falling droplets are not forming at the midpoint as opposed to this morning when it was -24C/-11.2F and a small puddle was collected in a tray.
 
Attached Images  
  #12  
Old 01-07-14, 07:14 PM
Member
Join Date: Apr 2011
Location: nj
Posts: 576
Received 0 Votes on 0 Posts
Either way the hole needs to be sealed up. Start there and move on.
 
  #13  
Old 01-07-14, 07:24 PM
Member
Thread Starter
Join Date: Jul 2013
Location: Canada
Posts: 15
Received 0 Votes on 0 Posts
Thanks RDSTEAM and NJ Trooper for all your help!

So the next step if I understand correctly is to insulate the pvc pipe. In terms of sealing the hole, are you referring to the hole in the ceiling or the hole were the pipe exits the house?
 
  #14  
Old 01-07-14, 07:29 PM
Member
Join Date: Apr 2011
Location: nj
Posts: 576
Received 0 Votes on 0 Posts
Where the piping exits through the house. This should have been foamed but it probably wasn't. Stop the cold air from getting in and insulate maybe the first few feet or so and that may solve your issues.
 
  #15  
Old 01-08-14, 06:45 AM
Member
Thread Starter
Join Date: Jul 2013
Location: Canada
Posts: 15
Received 0 Votes on 0 Posts
  #16  
Old 01-08-14, 09:56 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 1 Vote on 1 Post
"Great Stuff" is a good sealant... BUT... it's 'messy'. Wear OLD clothes and EYE protection (at a minimum). Wear nitrile gloves. If it goes somewhere it shouldn't, LEAVE IT ALONE! DO NOT attempt to wipe it up! You WILL make a much bigger mess that you can't clean up if you try. Let it be and harden and clean up afterward.

The biggest drawback to it is that the cans DO NOT WORK if not held UPSIDE DOWN. I wish they had a longer 'straw' on the applicator because it's almost impossible to use the stuff where you don't have much room to work and still hold the can upside down.

I have no experience with that pipe wrap.
 
  #17  
Old 01-12-14, 07:31 AM
Member
Thread Starter
Join Date: Jul 2013
Location: Canada
Posts: 15
Received 0 Votes on 0 Posts
Thanks again, both of you for all your help.

I was able to wrap the insulation around some of the PVC piping and spray the insulation foam where the pipe meets the wall.

In one area the installers had the pipes weight down against the electrical wiring (the hot exhaust one) so I placed a piece of wood to raise it so there is now slack on the wires. Is that okay or will elevating the pipe like that cause an issue?

I also put flex tubing around the electrical wires just in case.
 
Attached Images   
  #18  
Old 01-12-14, 08:55 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 1 Vote on 1 Post
Is that okay or will elevating the pipe like that cause an issue?
What do the installation instructions for the boiler have to say about 'pitch' of the exhaust pipe?

This is not a heating boiler, is it? Looks like a high efficiency water heater to me.

What's the make/model of the appliance?

A 'possible' issue with condensate INSIDE the exhaust pipe.
 
  #19  
Old 01-12-14, 10:02 AM
Member
Thread Starter
Join Date: Jul 2013
Location: Canada
Posts: 15
Received 0 Votes on 0 Posts
It is a high efficiency power direct vented water heater. GSW Model: 6G5065SN-PDV-02 (Cat No. B5912) as listed here

I am unable to locate any information regarding the pitch of the exhaust pipe....

What would be the worst case scenario if condensate builds up inside the exhaust pipe? How serious could this be?
 
Attached Images  
  #20  
Old 01-12-14, 11:07 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 1 Vote on 1 Post
What would be the worst case scenario if condensate builds up inside the exhaust pipe? How serious could this be?
Not sure how serious really...

Do you have the manual? It would be very strange that there is no info on venting in the manual!
 

Last edited by NJT; 01-13-14 at 08:45 AM.
  #21  
Old 01-12-14, 01:33 PM
Member
Join Date: Apr 2011
Location: nj
Posts: 576
Received 0 Votes on 0 Posts
I'm sure there's a condensate drain on the inducer fan. Most installs would require you to climb in height so there would be an area where the condensate would drain back towards the unit.
 
  #22  
Old 01-13-14, 08:44 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 1 Vote on 1 Post
Here's the water heater manual, it does appear they want 1/8" rise per 5' minimum, with no 'valleys' in between the appliance and the vent terminal.

http://www.gsw-wh.com/downloads/PDF/317898-000.101.pdf
 
  #23  
Old 01-14-14, 05:23 PM
Member
Thread Starter
Join Date: Jul 2013
Location: Canada
Posts: 15
Received 0 Votes on 0 Posts
Thank you for providing the link to the manual. It does not appear that I have any valleys and since they require a minimum rise it looks like I am good.
 
  #24  
Old 01-14-14, 06:15 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 1 Vote on 1 Post
I think so too.

Let us know how the insulation works out.
 
  #25  
Old 01-15-14, 06:21 AM
Member
Join Date: Mar 2009
Location: USA
Posts: 675
Received 1 Vote on 1 Post
The condensation

This is just an aside. I had this experience with foam sealants. I needed to get foaming a place further than the plastic pipe was long. I had nothing to loose, so I slipped a 3" piece of plastic tubing luckily the right size, and it worked. The foam ran the three feet through the pipe with no problem. I don't know how much further it might have went.
Sid
 
  #26  
Old 01-15-14, 06:58 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 1 Vote on 1 Post
I've done similar too Sid... but had a bad experience...

You have to feed the foam through the tube VERY SLOWLY, which is difficult to do with that nozzle setup...

If you feed it too fast, the tubing literally BLOWS OFF the spout and you end up with that foam stuff splattered all over the place... and pray you don't get it in your eyes!

If anyone decides to try this, a FULL FACE SHIELD with coverage around the sides as well is ABSOLUTELY NECESSARY!

Did I mention? DON'T GET IT IN YOUR HAIR!

I think it's a bit dangerous to suggest actually... and is why I didn't... sounds good in theory...

But may in fact be a "Darwin Award Moment".
 
  #27  
Old 01-19-14, 03:17 PM
Member
Thread Starter
Join Date: Jul 2013
Location: Canada
Posts: 15
Received 0 Votes on 0 Posts
It is -3C (26.6F) outside. Right at the end of the pipe/insulation where the cold water heater intake exits the wall I can feel droplets of water. On the other cold furnace intake pipe where it exists the house, when I press my finger against the insulation water droplets fall out. UPDATE: I just went back and checked and droplets that are falling out from the insulation is at the part where I had used a small bit of insulation initially and then needed to join in the middle (non-continuous wrap). The other parts of the insulation appear ok as when I press against it no water droplets fall out. I guess I will need to wrap one continuous piece over the existing insulation...

Is this normal? Will there always be condensation which will build up between the pipe and insulation?

Looking through the holes in the ceiling to see further down the pipe, in areas where there is no insulation I don't see any condensation. It might not be cold enough...later this week it may get to -20C (-4F) so I will see how the rest of the pipes are at that time.
 
Attached Images  

Last edited by rstor; 01-19-14 at 04:38 PM.
  #28  
Old 01-19-14, 03:36 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 1 Vote on 1 Post
Is this normal? Will there always be condensation which will build up between the pipe and insulation?
Normal? Depends on what exactly you mean...

It's physics. Any time that warmer moist air contacts a surface that is below the dew point of the air, water will condense out of that air. So normal, yes, I guess it is.

Will it always occur? Unless you can completely insulate the pipe and prevent room air from infiltrating the insulation, then yes, it will always occur when the pipe gets colder than the dew point of the surrounding air.

But I think you know that already?

The only solution to your problem is going to be 100% insulation coverage of enough R value to prevent the condensation, along with 100% 'vapor barrier' to prevent the room air from infiltrating the insulation.
 
  #29  
Old 01-19-14, 03:42 PM
Member
Thread Starter
Join Date: Jul 2013
Location: Canada
Posts: 15
Received 0 Votes on 0 Posts
So basically covering the pipe with insulation at certain segments will only prevent or diminish condensation from forming at those insulted segments, correct?
 
  #30  
Old 01-19-14, 03:50 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 1 Vote on 1 Post
Yes. As long as there's a cold pipe, and warm moist air around it, there will be condensation.

I know it's a little late now to bring this up, and I don't know if it's offered with your appliances or not, but there are exhaust / intake products available that are 'concentric', where the intake pipe is inside the exhaust pipe. The intake pipe would still condense (even more actually, due to the high moisture content of the exhaust gases), but it would be inside the exhaust pipe and would drain back to a collection point to be dispensed with.
 
  #31  
Old 01-19-14, 04:02 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 1 Vote on 1 Post
The install manual does show a concentric vent termination on page 12.

This would probably serve to also warm the incoming air as it passes over the exhaust pipe.

Looking at the pictures, it seems those intake and exhaust are fairly close together. Are the intake and exhaust on the outside of the building at least 8" apart as shown on page 11, Figure 7 ? (not that it makes a difference with the current problem, but if it's wrong per the installation manual, maybe you have a case to get the installers back to make it right?... and ask them to use the concentric termination instead of the two separates? Might have to pay a little more, but if it solves the problem... just sayin')
 
  #32  
Old 01-19-14, 04:36 PM
Member
Thread Starter
Join Date: Jul 2013
Location: Canada
Posts: 15
Received 0 Votes on 0 Posts
Thank you for suggesting the concentric vent option.

I've measured the exhaust and intake for both the water heater and furnace and they are positioned in such a way so that the exhaust and intake are 17 inches apart outside the house.

My main concern is the condensation that was falling at the points where the ceiling was cut which resulted in water droplets falling on my equipment. It seems to occur further down the pipe only when it is extremely cold. I am not too worried about the rest of the pipe run where droplets of water falling would land onto the ceiling (as this would occur infrequently when it is extremely cold).

Hopefully the insulation will be enough at the open parts and I will go over the insulation again with more (for the furnace intake) closer to the wall where it appears to be the coldest.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
 
Ask a Question
Question Title:
Description:
Your question will be posted in: