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Downsize a chimney liner?

Posted by bepeace (My Page) on
Mon, Jun 24, 13 at 1:41

Note - I posted this in "Fireplaces" but this forum may have more readers.My 1920s home currently has the furnace (from the 50s- 60s) and the hot water heater venting (I think that's the correct term) into the chimney.
I am having a new furnace and A/C installed this week. The furnace will now vent outside the house, leaving only the hot water heater going into the chimney.

The question is: do I need to downsize the chimney liner? I have researched quite a bit and it's about 50/50 - yes and no. The "no" votes say only a flue cap is needed, while the "yes" votes (all 'votes' are by professionals) have the same reason - to minimize gases, etc, from escaping, etc.

The other comment is that there is a small amount of water/condensation at the base of the chimney in the basement. I am having the roof checked for leaks in about a week.

Any advice on the chimney liner is welcome. Two last questions - 1) is stainless steel the way to go - or is aluminum okay? 2) Should I let the HVAC team install the liner or should I leave that for a chimney professional?

Thank you!


Follow-Up Postings:

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RE: Downsize a chimney liner?

I am assuming your fuel source is natural gas.Talk to your installer about a tankless on demand direct vent hot water heater.You will not need a chimney. I know that SS liners can be pricey along with several other factors,ie life of your current hot water heater, cost of running your current heater vs the tankless , convenience of the tankless (continuous hot water). Many utilities and states offer some pretty good rebates on energy efficient appliances.


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RE: Downsize a chimney liner?

What you aren't telling us is this: is the chimney used with a fireplace? A usable fireplace needs a certain amount of flue area to draw properly...if you use one, I'd be wary of downsizing the flue without an expert's advice.

And when you say there is 'condensation' at the bottom of the chimney, are you talking at the base of the wall, or in the old cleanout opening, or the hole where the old vent flue for the furnace entered?

My parlor chimney has a gas fireplace, and the second flue in it was used for the old furnace, which is now replaced with a direct vent one, and the condensate from it flows through a small pipe to my corner basement drain. The water heater vents to a second chimney which also vented the old stove. I would like a tankless water heater, but can't afford the price--and I've heard that they can take a few minutes to get you hot water.


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RE: Downsize a chimney liner?

Hi columbusguy1 - I bought this home 2 years ago and have never used the fireplace, but it is both gas and wood burning. The 'condensation' is near the 2 cleanout openings, but sometimes runs along the width of the chimney at the base of the chimney where it meets the floor. I just checked it again and both the furnace and the large galvanized metal 'pipe' from the top of the hot water heater goes into the left side of the chimney, while the gas pipes (copper) from the hot water heater goes into the right side of the chimney.

jonnyp - I did get several recommendations to do a tankless hot water heater, but I have a $200 (he's giving me a break) cost for an aluminum liner from the A/C furnace installer and a $425 for stainless steel quote from a masonry guy (who still needs to see it in person). Both have great reviews on angieslist and other sites and both seem very reputable, but I am wondering if I should let the masonry guy install (if needed) the liner and not the A/C furnace guy?

Thanks to both of you for your help!


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RE: Downsize a chimney liner?

Each fuel burning appliance and fire place must have its own flue/chimney; by law a flue/chimney cannot be shared.

The masonry "chimney" probably has one or two separate flues for gas appliances and a larger one for the fireplace with an ash dump at the basement level. You must look at the top to determine the sizes.

The size of a chimney flue is determined by the size of the fireplace opening and a vent flue by the size of the appliance.


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