The mikveh (ritualarium) is the ultimate symbol of Jewish purity today. This article will discuss the basic requirements of constructing a mikveh. In the next issue we will discuss some of the modern-day methods used to construct a mikveh that complies with current hygienic standards.

Ma'ayan and Mikveh
The Torah (Vayikra 11:36 as explained by Sifra, Shemini, Parsha no. 9) presents two methods of purification through immersion. The first is a ma'ayan, a body of flowing water. The second is a mikveh, a body of standing water. The Sifra explains that a ma'ayan and a mikveh operate differently. A ma'ayan is only valid if it is comprised of naturally flowing water. A mikveh is only valid if it is comprised of standing water. Based on the comments of the Sifra, a ma'ayan that is not comprised of natural flowing waters is invalid. Similarly, a mikveh whose water is flowing is invalid.

Another difference between a ma'ayan and a mikveh is the requisite amount of water. The Sifra as well as the Mishna, Mikva'ot 1:7, state that a ma'ayan has no requisite amount of water. However, a mikveh is not valid unless it contains forty se'ah (approximately 200-250 gallons). [Rivash, in his responsa, no. 292, claims that the lack of a minimum requirement of water for a ma'ayan is a function of a ma'ayan being composed of flowing water. R. Chaim Soloveitchik, Chiddushei Rabbeinu Chaim HaLevi, Hilchot Mikva'ot 9:6, in explaining Rambam's opinion, does not view the requisite amount of water as a function of flowing water. See Kehilat Ya'akov, Taharot no. 50.]

The Status of Rivers
A river is a body of flowing water and should constitute a ma'ayan. However, use of a river for immersion is all but simple. The Gemara, Nedarim 40a, cites numerous opinions as to whether a river constitutes a ma'ayan. The central question in this discussion is whether the majority composition of the river is rain-water or water that originated from its original source. If majority of the water in the river is rain-water, the river cannot be considered a ma'ayan. If majority of the water in the river is water that originated from the source of the river, the river can be considered a ma'ayan. The various opinions in the Gemara argue about what is considered "rain-water" and which seasons present a concern that there is majority "rain-water" in the rivers. The Gemara notes that if a river does not constitute a ma'ayan, the river can be converted into a mikveh by enclosing a portion of the river so that the flow of water is stopped within the enclosure.

Shulchan Aruch, Yoreh De'ah 201:2, rules that one should not immerse in a river that is mostly rain-water. Rama, ad loc., rules that if there is no available mikveh, one may rely on the opinion that a river is always comprised of a majority of water from the original source of the river. Rama adds that one may not apply this leniency to a river that originates from surface runoff since the entire flow ceases during the dry season.

A Mikveh with Flowing Water
As mentioned previously, a mikveh is only valid if the water is collected. In this section, we will focus on three discussions regarding a mikveh that may be invalid because of flowing waters. First, The Mishna, Mikva'ot 5:5, alludes to the invalidity of a mikveh that contains a leak because the water is now flowing water (see the comments of Rash, ad loc.). Rabbeinu Asher, in his responsa 31:4, claims that one can only entertain invalidating a mikveh due to a leak if the nature of the leak is such that the mikveh will eventually contain less than the requisite forty se'ah of water as a result of the leak. Mordechai, Hilchot Niddah no. 745, disagrees and invalidates any leak even if it will not affect the minimum requirement of forty se'ah. Shulchan Aruch, Yoreh De'ah 201:50, codifies the opinion of Rabbeinu Asher. Rama, ad loc., notes that one should ideally be concerned for the opinion of Mordechai.

Second, Rashba, Sha'ar HaMayim no. 2, rules that if there is a small leak in the mikveh such that the depletion of water is not recognizable, the mikveh is valid. Rashba's ruling is codified by Shulchan Aruch, Yoreh De'ah 201:51.

The Vilna Gaon, Biur HaGra ad loc., questions the ruling of Shulchan Aruch. Rashba, in presenting his opinion, states that he too is of the opinion that any leak is invalid even if forty se'ah will remain in the water. As such, there is room to distinguish between leaks that are recognizable and leaks that are not recognizable. However, Shulchan Aruch follows the opinion of Rabbeinu Asher that a leak that does not affect the requisite amount of water does not invalidate the mikveh. Therefore, there should be no reason to distinguish between leaks that are recognizable and leaks that are not recognizable. If the leak will eventually deplete the mikveh of the requisite amount of water, the mikveh is invalid. Otherwise it is valid.

R. Ovadia Yosef, Yabia Omer, Yoreh De'ah 8:18, cites numerous Acharonim who were not concerned for the question of the Vilna Gaon and permit a leak that is not recognizable even if it will eventually deplete the mikveh of its forty se'ah. He also cites some Acharonim who were very meticulous to inspect the mikveh for even the slightest leakage. R. Yosef concludes that a mikveh with an unrecognizable leak is valid, but it is preferable to repair the leak.

Third, Rivash, op. cit., states that if there is water that is flowing out of the mikveh but returning back to the mikvah, the mikveh is valid. Rivash's ruling is codified by Rama, Yoreh De'ah 201:50. As such, if a mikveh contains a water pump that filters the water by pumping the water out of the mikveh, through the filter and back into the mikveh, one would not consider the mikveh invalid due to flowing water. [R. Moshe Feinstein, Igrot Moshe, Yoreh De'ah 1:110, rules that one should nevertheless disable the filter prior to immersion because he has a minor doubt that the filter may be problematic.]

Drawn Water
The Mishna, Mikva'ot 2:4, states that if three lugin (a log is the volume of six eggs) of drawn water are placed into a mikveh that is lacking forty se'ah, the mikveh is invalid. There is a dispute among the Rishonim as to whether the invalidity of drawn water is of biblical origin or of rabbinic origin. Rabbeinu Yitzchak (cited in Tosafot, Pesachim 17b, s.v. Ela) is of the opinion that the invalidity of drawn water is only rabbinic in nature. Rabbeinu Asher, Hilchot Mikva'ot no.1, is of the opinion that if majority of the water that comprises the first forty se'ah of the mikveh is drawn water, the mikveh is invalid on a biblical level. If majority of the water is not drawn water, but three lugin of drawn water entered the mikveh, the mikveh is invalid on a rabbinic level. [There are other opinions among the Rishonim. See Sefer HaYashar, Chiddushim no. 671, Rash, Mikva'ot 2:3, and Ra'avad (cited in Ran, Shavuot 5a).]

The practical difference between the opinion that drawn water can invalidate the mikveh on a biblical level and the opinion that it can only invalidate on a rabbinic level is with regards to doubt. According to Rabbeinu Yitzchak, if there is a doubt whether the mikveh is comprised of drawn water, the mikveh is valid. However, Rabbeinu Asher notes that if the doubt extends to whether majority of the mikveh was filled with drawn water, the mikveh is invalid. Rama, Yoreh De'ah 201:3, codifies the opinion of Rabbeinu Asher.

Due to the invalidity of drawn water, water that is used for a mikveh is generally gathered from rain-water that enters the mikveh through pipes. The Mishna, Mikva'ot 4:2, states that water that runs through pipes is valid and is not considered drawn water as long as the pipes don't contain grooves or pockets that collect water.