# Is the condensate that comes from my HE furnace safe for plants?



## aboekman (Mar 18, 2012)

I like using distilled water for my plants. Is it just distilled water coming from my furnace or is there nasty contaminates/exhaust in it.

Thanks.


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## joecaption (Nov 30, 2011)

It's not distilled but will do no harm to your plants. It's condinsation from the air.


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## aboekman (Mar 18, 2012)

joecaption said:


> It's not distilled but will do no harm to your plants. It's condinsation from the air.


Okay thanks. Aren't condensation and distilled water the same thing?


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## HVACDave (Oct 16, 2007)

HE furnace condensate is not the same as distilled water. It also contains acidic properties due to the combustion process which your plants may not like. It will actually eat away brass fittings on condensate lines etc. so you may want to try it on a plant you don't particularily like very much.

Air conditioning condensate on the other hand would work very nicely.


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## REP (Jul 24, 2011)

HVACDave has it right on this question.
Furnace condensate is acidic.It would be like watering your plant with orange juice or tomato juice.
I do not think they would last too long.


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## hvac benny (Dec 29, 2009)

HE furnace condensate contains carbonic acid, and will, like HVACDave said, eat through brass; so probably not very plant friendly.


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## M3 Pete (May 10, 2011)

aboekman said:


> Okay thanks. Aren't condensation and distilled water the same thing?


If condensation is from the air, the answer is yes, the condensate is virtually pure water. Thus, your air conditioning condensate is pretty close to distilled water, because it is simply the water vapor in the air condensing on the cold AC element. 

Furnace condensate, however, is produced by the combustion of natural gas (methane), which produces mostly CO2 and water vapor. (CH4 + 2 O2 --> 2 H2O + CO2). The water vapor condenses as the heat is pulled out of the combustion gases (HE furnaces produce lots of condensate because they pull so much heat out of the combustion gases, so less water vapor goes up the flue). 

But the water and water vapor has lots of contact with the CO2. 

CO2 + H2O --> H2CO3, which is carbonic acid. So furnace condensate has a pH of about 4, roughly the same as soda pop.


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## bobelectric (Mar 3, 2007)

Would that be the same about using water from my basement dehumidifier?


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## sktn77a (May 11, 2009)

No, water from a dehumidifier or AC evaporator is pretty much pure distilled water; water from the high efficiency furnace condensate is weak carbonic acid as M3 Pete has so eloquently described.


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## REP (Jul 24, 2011)

Water from the tap is water that has run over rocks and minerials picking up trace amounts of iron, calcium,lime etc.
Water that is heated to a steam or gas or evaporated into a gas leaves the mineral content behind.When this gas condenses back to a liquid it is free of minerials.This is what distilled water is.


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## beenthere (Oct 11, 2008)

Water from A/C condensate is not as pure as you might think. Think about how dirty the coil can get.


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## M3 Pete (May 10, 2011)

REP said:


> Water from the tap is water that has run over rocks and minerials picking up trace amounts of iron, calcium,lime etc.
> Water that is heated to a steam or gas or evaporated into a gas leaves the mineral content behind.When this gas condenses back to a liquid it is free of minerials.This is what distilled water is.


yes, that is distilled water. And water from an A/C unit or electric dehumidifier is essentially the same thing, taking water vapor out of the air (but it might have some dirt in it, as beenthere points out).

But HE furnace condensate is not from water turned to steam. It is one of the combustion products of the natural gas used to power the furnace. Like distilled water, it won't have any minerals in it, but it has a lower pH (acidic) and may have a few other combustion product residuals in it as well (in very minor amounts).


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## Varski (Feb 10, 2021)

M3 Pete said:


> yes, that is distilled water. And water from an A/C unit or electric dehumidifier is essentially the same thing, taking water vapor out of the air (but it might have some dirt in it, as been there points out). But HE furnace condensate is not from water turned to steam. It is one of the combustion products of the natural gas used to power the furnace. Like distilled water, it won't have any minerals in it, but it has a lower pH (acidic) and may have a few other combustion product residuals in it as well (in very minor amounts).


Will the acid in the water created by furnace combustion evaporate or dissipate over time? Currently considering connecting four 55 gallon drums to the condensate pump to create an emergency water supply. This would be a mix of winter Furnace water and summer AC water. Is there something to add to the drums to make the water safe for flushing toilets or even drinking?


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## joed (Mar 13, 2005)

A 9 year old thread.


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## yuri (Nov 29, 2008)

I doubt anyone has come up with this idea to re-use furnace water or tried it so no one can tell you if it is plausible.

You get very little water out of a gas furnace anyway. An AC unit produces several gallons a day and my gas furnace in Canada where it is very cold and runs a lot may produce a quart/litter of water a day. Not worth the trouble IMO.

When it is running it barely even trickles out.


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## lenaitch (Feb 10, 2014)

Varski said:


> Will the acid in the water created by furnace combustion evaporate or dissipate over time? Currently considering connecting four 55 gallon drums to the condensate pump to create an emergency water supply. This would be a mix of winter Furnace water and summer AC water. Is there something to add to the drums to make the water safe for flushing toilets or even drinking?


Not a chemist but I doubt the acid will dissipate over time. It may break down but that might come at the cost of the steel drums. There are ways to neutralize the acidity - limestone is one - but you would have the research the science, particularly if you plan on drinking it.


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