According to the Larousse Dictionary (The Hard Copy, not from Google, the web is not the most trustworthy place to get information) Natural gas (this is the gas used for most Furnaces in the world) is mainly Methane which is CH4 so:

CH4 + 2O2 --> CO2 + 2H2O + Energy (this energy in form of flames condensates water from the surrounding environment which is most of the water pumped out to the drain plus the 2 parts from chemical reaction)

It is clear that Carbonic Acid (H2CO3) is not a byproduct of the above chemical reaction. Just for illustrative purposes carbonated Colas have lots of carbonic acid in it, and is safe to drink them. Also our body have the biochemistry necessary to metabolize this carbonic acid, besides I have drank it my self and my dog drink it every day for years and we are both healthy. On top of everything I have performed several lab test on all these waters and they are safe to drink, so you dear Chicklet are just wrong, sorry.

hey there, read you advice on the cheapskate blog. You may want to be careful about counselling someone to consume the water that is coming from your furnace. It is not WATER, it is carbonic acid. Products of combustion ARE NOT drinkable water. Google that. It is dangerous enough to harm you. Although the water coming from your AC and humidifer are OKish. It is not recommeded that you consume that. Again water coming from your furnace is NOT condensation from air but a byproduct of gas and oxygen! DO NOT DRINK - even from a clean container!!!!!!!

Welcome to SC!!!