Draft problem


  #1  
Old 08-12-02, 06:57 PM
Gary Larson
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Draft problem

Dear DIY'ers
I have a drafting problem with my gas hot water heater. It is a 50 gallon unit that was installed in March 2001 (Rheemglass Standard). The gas hot water heater and my gas water boiler (not sure of BTU's on boiler, but brand new unit installed in July 2001) are located in my utility room on the basement level. I believe the water heater uses a 3" metal pipe that leads to my chimney, and the boiler has a 6" metal pipe. Both were put in by previous owners as a requirement in order for me to purchase the home last year.

When the gas hot water heater ran for the the last year or so, there always was a slight detectable smell (exhaust, not gas), but nothing to cause alarm.

This past weekend, I sealed up the room airtight to prevent mice from entering the room (we have a large wooded area as our backyard) via insulation, plywood and several cans of Dow Great Stuff expanding foam. When the room was finished and the gas hot water heater started, the exhaust was very bad and it permeated throughout the entire house. My guess is that the room had so many holes in it that any exhaust would go right out; now it has no place to go.

Some things I have looked into already:
1) The 3" metal pipe from the hot water heater to the chimney; removed it - nothing blocking it, nor inside the cement pipe that in "inside" the chimney. I duct-taped all seams on the metal pipe.
2) Opened the window inside the utility room, to provide ample fresh air to the heater so that it has a source to draw the air up into the chimney.
3) Plumber came over; hot water heater is functioning correctly. However, when he lit a small piece of newspaper near the draft hood the smoke was not drawn up into the pipe.
4) Removed the 6" pipe coming from the boiler, since it has a better view of the chimney, and is closer to the bottom of the chimney (the 3" pipe from the hot water heater enters the chimney above the 6" pipe). Went up on my roof, removed the cap, looked for obstructions - nothing. Lowered my utility light down the chimney. Went down to my utility room and the light was facing me when looking through the pipe (thus nothing was blocking it). There were some seams or cracks in the tile from what I can see inside the chimney while looking through the 6" cement pipe (note it was just the tile; the exterior chimney itself that is covered in cement does not have any apparent cracks). Also, at the end of the 6" cement pipe inside the chimney, there is excess cement piled up (perhaps restricting 1/3 of the cement pipe) at the end. However, there seemed to be plenty of open area at the end of the 6" pipe for exhaust to go out.
5) Inside the 6" cement pipe that leads to the chimney, I lit a small piece of newspaper on fire, and it DID draw the smoke towards the chimney.

What is left? Is my chimney size not correct? Need a new liner? If liner, can I get away with a metal one rather than new tile? Any idea on costs?

Any info greatly appreciated
 
  #2  
Old 08-12-02, 07:11 PM
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flue problem

i would assume at this time of year your boiler is not operating. do you have 1/4 inch per foot MINIMUM rise from the water heater to the chimney? do not close off this area airtight as the appliances need combustion air. flue odor throughout the house sounds like voids in the chimney leaking into the living area. these fumes could very well carry carbon monoxide, so this is a serious situation. sounds like you may need a chimney liner (metal) to tie your flues into. can you call the installer of the boiler to take a look? he was there only a year ago, may come out for free.
 
  #3  
Old 08-12-02, 07:58 PM
Gary Larson
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hvac4u - thanks for prompt reply.

1) Correct, boiler is not operating now.
2) I believe that there is a 1/4" rise for every foot. The pipe from the hot water heater to the chimney is 4'. After the draft hood, the pipe rises, and quick look with my measuring tape shows about a 2" rise. which would meet your minimum (as the plumber came in today and inspected it, I assume he would have mentioned that the rise was not sufficient).
3) When I say airtight, I mean the wall that is facing the backyard, where the mice were coming in (and where the exhaust previously was most likely going out). There are two doors leading to the utility room (one from the garage and one from the upstairs) that are not airtight, so there should be a sufficent air coming in through there. Also, with the window in the utility room itself wide open (which I hope to close and not leave open all the time), there should be sufficent air for the draft, but still the exhaust is still not going up the pipe. The water pipes, etc that go through the ceiling of the utility room, etc have holes that are slightly larger than the pipes (which I did not fill, as the mice are not entering that way), so those holes are most likely the way the exhast smells are getting to the rest of the house.
4) When you mention that the chimney may be leaking and thus the smell through the house, I do not believe this is the case, as the exhaust is not being drawn into the chimney at all.
5) The installer/main plumber of both the hot water heater and boiler is away, and thus I got the backup to look at the unit. I am hoping to speak to him when he gets back.
6) Any idea how much a new liner installed would run me? My wife made an appointment with the Chimney Doctor, the guy who cleaned our fireplace/wood burning chimney (this is separate from the hot water heater/boiler chimney). The appointment is this Thurs, but my main plumber (the guy who installed the units) comes back from vacation next week. I am concerned that the chimney guy will push for a new liner, whereas the plumber may have a more economical solution, but I will not get to speak to the plumber till after my appointment w/ the chimney guy.

Any ideas??
 
  #4  
Old 08-13-02, 06:46 AM
Gary Larson
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Photos attached

HVAC4U, anyone else out there,

I took some photos of the draft hood, and a friend (who is not a plumber but is quite handy) suggested that the gap (perhaps an inch?) was too high up, and that the hood should be lowered. Is there code that states how low a draft hood should be to encourage draft, yet not too high so that fumes don't escape?
 
  #5  
Old 08-13-02, 07:11 AM
Gary Larson
Visiting Guest
Posts: n/a
Photos attached

HVAC4U, anyone else out there,

I took some photos of the draft hood, and a friend (who is not a plumber but is quite handy) suggested that the gap (perhaps an inch?) was too high up, and that the hood should be lowered. Is there code that states how low a draft hood should be to encourage draft, yet not too high so that fumes don't escape?
 
 

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