Question: May one add chlorine to a mikvah?
Short Answer: Although one may not add anything to a mikvah that changes the color of the water, it is permitted to add clear chlorine to a mikvah, especially if it absolutely does not change the appearance of the water.
I. Color Change
The Mishnah (Mikvaos 7:3) states that if wine or olive juice falls into a mikvah and changes the appearance of the water, the mikvah is invalid (pasul).
The Shulchan Aruch (Yoreh Dei’ah 201:25) codifies this halachah, adding that the mikvah is invalidated based on this color change, even if it has 40 sa’ah otherwise (without the juice). The Shach (66) adds that the mikvah is invalid even if the water does not look like the juice but just no longer appears like water.
The Shulchan Aruch (ibid) adds that you can make the mikvah kosher in such a case (where there otherwise is 40 sa’ah) by adding additional water, even tap water, to bring the color back to the color of water.
II. Biblical or Rabbinic?
Does this color change invalidate the mikvah on a d’Oraisa or d’Rabbanan level?
The sefer Mikveh Mayim (Vol. 3, pp. 76-90) discusses this question. The Kiryas Sefer (Mikvaos 7) and the Levush (201:25) both clearly hold that changing the color of a mikvah invalidates the mikvah on a d’Oraisa level. The Levush cites the pasuk “mikveh mayim,” that the water must look like water. Notably, the Beis Yitzchak (2:42:11) limits the p’sul d’Oraisa to where the mikvah completely changes its appearance. If the mikvah just changes its appearance a little bit, the mikvah is invalid, but only on a d’Rabbanan level.
On the other hand, the Raavad (in Baalei Nefesh) writes that the mikvah is invalid because it looks like the mikvah is filled with other liquid and not water. This is a d’Rabbanan invalidation. So writes the Tosfos Yom Tov (Mikvaos 7:3) and Tiferes Yisrael (ibid).
The Igros Moshe (Yoreh Dei’ah 1:120:8) brings a proof from Tosafos in Z’vachim (79a) that a mikvah that changes colors is invalidated on a d’Oraisa level. The Gemara Z’vachim (79a) discusses the rules of bitul, where one object is nullified in another. The Gemara cites three examples: (i) taste; (ii) majority; and (iii) appearance. The Gemara explains that when one item mixes with a different item (min b’she’eino mino), the smaller item is nullified in the larger item where there is no trace of the taste of the smaller item. When two of the same objects mix, and one item is a majority, the other item is nullified. Additionally, when another liquid mixes with water in a mikvah, the liquid is nullified unless it changes the appearance of the water.
Tosafos wonders why we list “majority” and not “1/60” (“shishim”). Tosafos explains that we are dealing with the laws of nullification on a d’Oraisa level. Accordingly, Rav Moshe understands that nullification based on appearance in the mikvah, which is in the same list in the Gemara, is also d’Oraisa. Rav Moshe adds that this is the opinion of the Rambam as well, as he never writes that this invalidation is only d’Rabbanan.
Based on the fact that most poskim understand that the invalidation is d’Oraisa, the Minchas Yitzchak (3:89:13) rules that a safeik whether the appearance changed (i.e., not sure why the water changed and because of what), is also invalid. Indeed, the Minchas Yitzchak also notes that we would likely rule stringently even according to the Raavad, as mikvah is a case where the person is in a “chezkas tamei,” i.e., before the person immerses, he or she is certainly in a status of tum’ah. We need a mikvah that is certainly kosher to remove this definite tum’ah status.
III. Change of Smell or Taste
But what is the halachah where the appearance of the water does not change but rather the smell or taste of the mikvah changes based on the addition of a different liquid into the mikvah?
The Gemara (Chulin 106a) states that water that is undrinkable even to an animal may not be used for n’tilas yadayim, but may be used for t’vilah (i.e., in a mikvah). Further, the Gemara (Shabbos 14b) writes that one may be tovel in dirty cave waters. Based on these Gemaros, the Rambam (Hilchos Mikvaos 7:1) writes that a change in the smell or taste of mikvah waters does not invalidate the mikvah. See Kesef Mishnah.
Similarly, the Shulchan Aruch (Orach Chayim 160:9) codifies these Gemaros, holding that dirty waters are not valid for n’tilas yadayim, but are valid for t’vilah.
Based on the above, the Minchas Yitzchak (8:76) permitted the addition of chlorine or other clear chemicals into the mikvah. Similarly, the Sheivet HaLevi (5:105) permits adding a clear “antibiotic” into the water if medically necessary for a particular woman.
Interestingly, the Mikveh Mayim (Vol. 3, p. 86, n. 10) queries whether clear chlorine may be added to the mikvah if there is a change in the color of the mikvah as a result. He suggests that perhaps it should be forbidden, as the Mishkenos Yaakov (Yoreh Dei’ah 46) ruled strictly about a mikvah where the waters changed their appearance from the heat. Even though other poskim, including the Chazon Ish (8:8), disagree and rule leniently that the heat does not ruin the mikvah, perhaps we are stricter here when the chlorine is an external additive. He concludes “tzarich iyun.”
Next Week’s Topic: May a mikvah melt snow to fill the mikvah instead of water (i.e., if there is not much rainfall)?