I've replaced my 82% efficiency gas furnace to a new 93% efficiency
model. Prior to this my old gas furnace and my hot water tank were both
vented through the chimney. Now, only my hot water tank is vented out
the chimney, while my new furnace is vented out the side of the house
through PVC pipes.

Are there any issues with having the hot water tank still use the
chimney? I didn't think so until I saw this article. I'm not an HVAC
person so I don't fully understand what is the issue with "Now the hot
water tank has to heat up that big chimney all by itself".

I don't know the specs of the hot water tank but I believe its around
13 years old.


Here's the full paragraph:


"Another hot water tank issue is when you switch from a conventional
gas furnace and hot water tank to a new, high-efficiency sidewall
vented furnace. Now the hot water tank has to heat up that big chimney
all by itself, and you probably will have to pay for chimney relining.
It is often better, when choosing a chimneyless furnace, to switch your
hot water tank to sidewall venting at the same time and seal the old
chimney closed. However, sidewall vented hot water heaters are more
expensive than conventional hot water heaters and can be noisier."

http://www.cmhc-schl.gc.ca/en/burema...ose/ce_048.cfm