Help - water heater flue pipe leak

[Cubfan_Mark]

Hi - I had my gas hot water heater moved about 4 feet a week ago. To do this, a new elbow or about 45 degree joint in the flue pipe metal tubing was made. I noticed when we're using hot water and the hot water heater is engaged, condensation begins leaking from a very small leak in this joint between flue pipe pieces. I will note that it has been very cold here in Chicago this week, and I'm not sure if that has anything to do with it. I checked my roof, and while there appears to be a good amount of ice around the cap, it still seems to be on.

My first question is, even if I didn't have the leak, this water would be running back into the water heater top - is this normal at times? I would think rust would be an issue.

Next, what is the recommendation on how to best seal the joints between vents. I thought just 3 screws would do. With CO passing upwards, I'm concerned some could escape into my unfinished basement.

Lastly, part of the flue vent rests on a wooden floor joist before running upward to the next floor. I would think this gets too hot for that to be acceptable.

Please let me know your thoughts, and thanks in advance.

Mark

 

[Leejosepho]

I noticed when we're using hot water and the hot water heater is engaged, condensation begins leaking from a very small leak in this joint between flue pipe pieces ...

My first question is, even if I didn't have the leak, this water would be running back into the water heater top - is this normal at times? I would think rust would be an issue.

A lot of condensation or melting ice or snow running down onto your WH is certainly not good, but getting up on the roof to remove the ice or snow would be extremely dangerous. You might just have to let that be for now, and do not place any rags for catching water on top of your WH!

Next, what is the recommendation on how to best seal the joints between vents. I thought just 3 screws would do. With CO passing upwards, I'm concerned some could escape into my unfinished basement.

As long as the flue pipes and their seams are in good condition and the female ends sit down over male ends, the kind of "leak" you are talking about is not going to cause any trouble. Just be sure the lowest pipe slips inside the next one and so on all the way to the top.

Lastly, part of the flue vent rests on a wooden floor joist before running upward to the next floor. I would think this gets too hot for that to be acceptable.

Something should be done about that right away unless you want your cow to be blamed for another big Chicago fire!

 

[Sponsor]

 

[Jimbo]

Next, what is the recommendation on how to best seal the joints between vents. I thought just 3 screws would do. With CO passing upwards, I'm concerned some could escape into my unfinished basement.

Lastly, part of the flue vent rests on a wooden floor joist before running upward to the next floor. I would think this gets too hot for that to be acceptable.

Mark

Flue joints are not sealed. The draw upwards creates a negative pressure so nothing escapes. Too many elbows, or too long a horizontal run compared with the total vertical rise is not good.

If this is double wall flue, the minimum clearance to combustibles is 1" and if it is single wall, the clearance required is 6". Who moved this for you?

 

[Cubfan_Mark]

Thanks for the feedback.

I had a Wisconsin certified plumber move this, though he's now informed me its generally the heating folks that do the vent work and he just connects the hot water heater.

I'm not sure I understand the difference between single and double wall flue? The furnace isn't connected to this flue. I would think I would at least need that 1" clearance from the floor joist.

I am thinking the flue venting should be an easy fix when I find an exerienced heating guy. If that leak in the joint is then fixed, I will just have to figure out the condensation problem as we don't want all of that coming back into the top of the water heater, correct.

Thanks!

 

[Leejosepho]

I had a Wisconsin certified plumber move this, though he's now informed me its generally the heating folks that do the vent work and he just connects the hot water heater.

Either way, a flue pipe should not be touching wood.

I'm not sure I understand the difference between single and double wall flue?

Double-wall is a pipe inside a pipe, and with an inch or so between the two. For example, you might have a 3" or 4" flue inside another 5" or 6" pipe where it passes through wood framing.

If that leak in the joint is then fixed, I will just have to figure out the condensation problem as we don't want all of that coming back into the top of the water heater, correct.

Those joints are never going to be air- or water-tight, and they are not related to your condensation or melting situation.

 

[Cubfan_Mark]

would you guess then be that there is snow/ice that is making its way in through the flue vent cap on the roof?

The condensation that comes down the flue pipe into the water heater - is that common - and are there any other consequences besides rusting at the top of the water heater?

Thanks.

 

[Jadnashua]

FWIW, the last boiler I owned, had a double-walled flue. The inner pipe was for exhaust, and the outer one was for combustion air (not the same as your typical double-walled flue pipe). The inner pipe was sealed so any combusion gasses wouldn't get to the inlet and to prevent condensation from leaking to the inlet.

 

[Leejosepho]

would you guess then be that there is snow/ice that is making its way in through the flue vent cap on the roof?

Possibly, but that is only my guess. I live just a little southeast of you, and we have had plenty of snow and ice over the past couple of weeks. But even if your cap is up in the clear, you might still have snow or ice melting and finding its way in around the pipe near where it goes through your roof.

The condensation that comes down the flue pipe [onto] the water heater - is that common - and are there any other consequences besides rusting at the top of the water heater?

I have an electric WH, so I do not know how common that might be. You might just take a look every once in a while and wipe away any accumulation that might be there, but do *not* place any rags there to catch it for you. Other people here might be able to tell you better, but I would not worry about a little moisture that will evaporate while the heater is running anyway. And of course, your bigger issue is the single-wall flue touching wood. Please do something about that ASAP!

 

[Cubfan_Mark]

Thanks for the feedback.

I'm moved the flue off of the wood. The flue piping tends to sag a little bit. My relative is going to get a metal piece to act as a support. We added more screws between the joints and the leaks are now going to the water heater. I am going to call an HVAC guy this week, as I think there is not quite enough slope in this 2.5 ft horizontal piece of tubing that then does a 90 degree turn. I was told it must drop 1/4" per foot, but I would think it should be even steeper for gas.

 

[johncap523]

Thanks for the feedback.

I'm moved the flue off of the wood. The flue piping tends to sag a little bit. My relative is going to get a metal piece to act as a support. We added more screws between the joints and the leaks are now going to the water heater. I am going to call an HVAC guy this week, as I think there is not quite enough slope in this 2.5 ft horizontal piece of tubing that then does a 90 degree turn. I was told it must drop 1/4" per foot, but I would think it should be even steeper for gas.

Condensation, if that is what it is rather than melting snow coming in, is a problem that needs addressing. The fact that you stated above that the furnace isn't in the same vent is a problem. A water heater cannot produce enough exhaust heat to warm an outside vent. (An outside vent is one that is on an outside wall as opposed to being inside of heated space or between to adjoining homes.) It's too cold in winter for the water heater to heat up enough to allow the exhaust to flow upward and so it condenses and condensation flows back down into the pipe and appliance. This will rot both the flue pipe and the appliance and can be very dangerous ultimately resulting in potential carbon monoxide issues.

If this is a masonry chimney it may need to be lined for this application. Alternatively you could use a B-vent, what is described above a dual wall vent. The second pipe acts to insulate the vent and should alleviate the condensation problem if installed properly.

A third alternative is to go to a direct vent water heater which would typically go through a side wall and abandon the vent that is the source of the condensation problem.

A fourth solution is to run the furnace into this vent, assuming it is within proximity and that the vent is suitable both in size and condition to handle it. In most cases the additional exhaist from the furnace is enough to heat the vent and create a positive draft eliminating the condensation problem.

Unfortunately NONE of this does anything to help your Cubs! ....sorry, couldn't resist.....