Q. Can one fill a Mikvah with water that formed and dripped directly from an air conditioner?

A. Chazon Ish (Y.D. Mikvaos 2: 137:13) debates the making of a mikvah using condensed steam water and considers it in principle permissible only that we don’t create a mikvah using something that our sages did not use in the past. However he agrees that once condensed they would not be considered “sheuvim” and would not disqualify an incomplete mikvah. Har Tzvi (Rishmei Shaila p.145) quotes a similar opinion in the name of Rav Chaim Ozer zt’l . However there (ibid. n. 10) he mentions that Horav Eliashiv zt”l would doubt whether condensed steam water or water emanating from an A.C. unit is considered water at all.

Mishne Halochos (3: 91) finds the words of the Chazon Ish contradictory and maintains that he also considers water created from condensation as non water and similar to fruit juices.

Horav Shlomo Miller’s Shlit”a opinion is that the condensed water per se is not “maim sheuvim” and would be permitted for mikvah use. In practice however, since the vapor condenses around cooling tubes and other pooling metal surfaces that are considered to be halachical vessels, they could transform that water into ‘sheuvim’ and should therefore be avoided.

Rabbi A. Bartfeld as advised by Horav Shlomo Miller Shlit”a