Question: What is the required depth of mikvah waters?
Short Answer: Water in a mikvah must be a certain height above the middle of the immerser’s body. Accordingly, many mikvaos are approximately four feet deep.
I. Ideal Depth
The Shulchan Aruch (Yoreh Dei’ah 201:1) rules that a mikvah must contain 40 sa’ah of water (i.e., somewhere between 600 and 1,000 liters, see sefer Mikveh Mayim, Vol. 3, p. 50-59). But may the mikvah be wide and shallow? Must the water in the mikvah be a certain depth? Obviously, the water must be deep enough that the woman can immerse her entire body in the water at one time, but must it be deep enough so that she can fully immerse while standing mostly straight?
The sefer Mikveh Mayim (Vol. 3, pp. 60-70) addresses these issues. [Much of what is set forth below is from this excellent sefer!] The Gemara (Nidah 67a) states that a woman must immerse in a normal, walking position (“derech g’dilasah”). The Shulchan Aruch (Yoreh Dei’ah 198:35) thus sets forth the ideal manner in which a woman should immerse: bending slightly in a standing position, thereby ensuring that the water reaches all parts of the body.
Based on the above, the Shulchan Aruch (Yoreh Dei’ah 198:36) and the Rama (Yoreh Dei’ah 201:66) require that the mikvah waters be deep enough that they are at least a “zeres” higher than the woman’s midriff.
II. How Large Is a Zeres?
The sefer Mikveh Mayim cites numerous opinions as to the size of a zeres. The Tosefta writes that it is half of an amah of six t’fachim, i.e., three t’fachim. Tosafos cites the Kalir who writes that it is a third of an amah of six t’fachim, i.e., two t’fachim. The Rashba, on the other hand, holds that it is half of an amah of five t’fachim, i.e., two and a half t’fachim.
While many Acharonim, including the Aruch HaShulchan (198:36), rule stringently, that the water must be at least three t’fachim higher than the woman’s midriff, the L’vushei S’rad “compromises” at two and a half t’fachim (b’dieved). The L’vushei S’rad notes that this minimum height is equal to ten “agudalim.” The Igros Moshe (Yoreh Dei’ah 1:106), however, rules that in extenuating circumstances, eight agudalim higher than the midriff are sufficient.
The Mikveh Mayim explains that ten agudalim equal approximately 9.5-10 inches (according to the Chazon Ish) or eight inches (according to Rav Chaim Na’eh).
III. Too High
But can the water be too high? In other words, is it a problem if the water reaches up to the woman’s head, thereby forcing her to stand fully erect in the mikvah, which is against the Shulchan Aruch (ibid)? The Divrei Yechezkel (40) addresses this issue. He rules that this is not a concern. Because all women invariably bend over a bit in the mikvah, regardless of the depth of the waters, the immersion is kosher.
However, in a different t’shuvah (11), the Divrei Yechezkel, as well as the Divrei Malkiel (2:58), suggest a potential solution. A mikvah should have two levels, one deeper level for taller women, and a shallow level for shorter women.
Of course, as noted by both the Divrei Malkiel (ibid) and the Sheivet HaLevi (as cited in Mikveh Mayim), the water should not be too deep as to pose a danger, as such a mikvah will cause the woman to not immerse properly because of fear.
IV. Practically Speaking
After gathering the opinions of many contemporary poskim, the Mikveh Mayim concludes that the ideal depth of the water in a mikvah is 47.5 inches (a bit less than four feet). The Mikveh Mayim adds that if the mikvah will have two levels, then the deeper level should be 48 inches (four feet) and the shallow level should be 44 inches (3.67 feet).
However, the Mikveh Mayim expresses concern that even four feet deep is not deep enough for taller women. He therefore proposes three levels in every mikvah: (i) 51-52 inches (4.25-4.33 feet); (ii) 48 inches (four feet); and (iii) 44 inches (3.67 feet).
V. Final Note
As a final note, if the mikvah is built in a way that the water is not deep enough, all hope is not lost. Both the Shulchan Aruch (Yoreh Dei’ah 198:37) and the Rama (Yoreh Dei’ah 201:66) allow, in extenuating circumstances, for the woman to immerse lying down if the mikvah is not the correct depth. [The precise method is outside the scope of this article].
What is considered extenuating circumstances? The Igros Moshe (Yoreh Dei’ah 1:106) writes that we are lenient to allow this method only if there is no other mikvah within a “mil” walking distance (approximately an 18-minute walk). When measuring by car, only if there is no other mikvah within an 18-minute car ride.
Next Week’s Topic: May one add chlorine to a mikvah?