do i need a water heater exhaust fan?

stillerzSeptember 25, 2006


I have a gas water heater in my basement that vents up through my chimney. My furnace does not vent through the chimney -- it is a direct venting system.

My question is: Should I buy some sort of exhaust fan or booster to make sure the water heater exhaust is forced up the chimney?

The reason I'm asking is becuase sometimes I use the fireplace to burn a duraflame, and I've noticed that the chimney has a downdraft and until I get an updraft going with burning newspaper, the logs blow smoke back into my house.

So, I was wondering if it is possible that the carbon monoxide from my water heater exhaust could be getting blown back into my basement also, in the same way?

How could I check this? And, if it was happening, how would I address it? Fan? or, something else?


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It's pretty simple to check.

All you need is a candle.

With the fireplace not burning, light a candle, hold it next to the water heater exhaust hood, and blow it out. The smoke should be sucked up the chimney briskly.

Now do the same thing with a fire in the fireplace. If the candle smoke moves away from the water heater exhaust hood, you have a problem. Solving that could be as simple as opening a window to provide make up air for the fireplace.

The downdraft from the chimney when it's cold is because it's cold. There's a plug of dense, cold air being held in place by the damper. When you open the damper, if you don't have a chimney with a naturally strong draft (most newer chimneys don't), you'll get a downdraft.

Use the burning newspaper to reverse the draft BEFORE you get your duraflame going.

    Bookmark   September 26, 2006 at 10:13AM
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a couple of more things, your chimmey in the basement offers less restrictiion then the 4 inch b vent on the water heater. So air is going to take the path of least resistance. Fireplaces are a little different, because sometimes the front opening is to large relative to the chimney size, and they dont draw properly, the fix to that is to decrease the size of the fireplace opening. Most of all, the easiest way to have a piece of mind is to by a carbon monoxide dector, and do the flame test like K suggested.

    Bookmark   September 26, 2006 at 10:21PM
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I live in a duplex and there is a furnace and two w.heaters , all gas, being exausted through the same chiminey. Periodically, (when the guy upstairs is using hot water) there is an extremely strong smell of exhaust coming from the second water heater. Which is also the farthest from the actuall chiminey. It is exhausted with an aluminum(i think) pipe and when i smell the gas, the pipe is hot enough to burn my hand upon touch. Is there a fan that i can attach to the water heater to prevent this from happening? The land lord dosent seem to care and i am afraid for the health of family. There is no fireplace associated with this chiminey but the guy upstairs furnace may also be connected to it. Help me please! send all corespondance to THANK YOU!!

    Bookmark   January 27, 2008 at 9:01PM
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Similar question. I own a 1896, 2 1/2 story frame home that had space heaters in all rooms going up a single multi-compartmented chimney. All access to the chimney are sealed except for the gas water heater located in the basement. The water heater exhausts well during most of the year; but when the outside temp reaches the hi 90's, we get CO2 in the house (CO2 alarms). In this case, I have been turning the water heater to "vacation" until the sun sets (I can turn on the water heater with no issues until the heat of the day the next day). How can I fix this?

    Bookmark   May 26, 2012 at 1:10PM
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