I would like to know if there are specific studies or research regarding the condensed water that is generated by air conditioners.

Many people feel that this water is acid and corrosive but could not find anything that confirms or denies this belief.

If someone could send me a link or document with a reliable scientific research would help me.

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    $\begingroup$ Acid? Why? Condensed water is essentially distilled water. $\endgroup$ Commented Jan 20, 2016 at 11:22
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    $\begingroup$ I suspect some people might think this because all that water dripping out of the AC unit over the course of a few years will begin staining/eroding whatever is in its path. That's just water being water, though. $\endgroup$ Commented Jan 20, 2016 at 12:09
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    $\begingroup$ Distilled water will dissolve carbon dioxide from the atmosphere, which could reduce the pH below 7. Here's a technical document for water stills $\endgroup$ Commented Jan 20, 2016 at 12:10
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    $\begingroup$ True, but I deliberately tried to avoid this topic. Anyway, this is not what people outside of chemistry mean by "acid". $\endgroup$ Commented Jan 20, 2016 at 12:14
  • $\begingroup$ Additionally, if it's central AC and the blower unit is shared with a high efficiency gas furnace, the condensate from the furnace is quite acidic due to sulfuric acid in the combustion gas. So they may be confusing that with the condensate that comes off during cooling since they usually come out of the same drain pipe. $\endgroup$
    – Andrew
    Commented Apr 13, 2021 at 17:44

1 Answer 1


Pure condensed water is neutral (pH 7). However, water in contact with air is slightly acidic (approximately pH 5.6) due to dissolved carbon dioxide $\ce{(CO2)}$. Remarkably, the same applies to rainwater.

Furthermore, water condensed from air is not pure. The condensing water collects small amounts of various airborne substances (soluble gases and vapours, dust, and even radioactive particles from radon decay). (Note the large volume of air that is passed through the air conditioner while a certain amount of water is condensed.) Usually, these substances do not significantly affect the pH of the water. However, when the air contains large amounts of pollutants, such as sulfur dioxide or nitrogen oxides (e.g. produced in industrial processes), the condensed water can become more acidic (like acid rain, which can have pH values of about 4).

By way of comparison, typical values for black coffee are about pH 5.0–5.1, and for orange juice about pH 3.3–4.2.

  • $\begingroup$ What about the unpleasant smell emanating from the shop floor after rinsing the floor with the water produced by the air conditioner? What is the reason for this smell? $\endgroup$ Commented Apr 13, 2021 at 20:03