Building and Maintaining Mikvaot - Part Two by Rabbi Chaim Jachter


This week we will discuss some of the basic rules for creating a Mikva.  We must emphasize at the outset the words of Rav Shlomo Dichovsky, a member of Israel’s Supreme Rabbinical Court.  He writes (Techumin16:112), “The building of Mikvaot today requires a combination of thorough Halachic knowledge and specific engineering knowledge and experience.  Hence, there are very few people who are regarded as competent in this critical area of Halacha.”  Indeed, fewer than ten people in North America are competent to supervise the building of a Mikva.  Maintaining a Mikva also requires special competence and vigilance.  These are indispensible elements of insuring the Kashrut of the Mikva.

Differences between a Mikva and a Maayan

The rules of constructing a Mikva emerge from a Pasuk (Vayikrah 11:36) that Chazal interpret as presenting two modes of ritual purification.  One is immersion in a Maayan (natural spring, such as the celebrated spring of the Ari z”l in Tzfat) the second is immersion in a Bor Mikva Mayim, a pit that contains a collection of rainwater.  We refer to a Bor Mikva Mayim simply as a Mikva.

There are two major differences between a Mikva and a Maayan.  A Maayan is effective even though it is running water but a Mikva, must be stationary (or Ashboren in the language of Chazal, Mikvaot 1:7-8).  Another difference is the amount of water that is necessary.  A Mikva requires a minimum of forty Saah of rainwater and no such minimum exists for a Maayan (ibid). 

The Rishonim debate whether a Maayan does not require forty Saah only for immersion of utensils (for ritual purity) or even for purification of people.  The Rambam (Hilchot Mikvaot 9:6) and the Raavad rule leniently but Tosafot (Pesachim 17b s.v. Ella) rule strictly.  The Shulchan Aruch (Yoreh Deah 201:1) and almost all of its commentaries rule in accordance with Tosafot but the Vilna Gaon (Biurei Hagra Y.D. 201:6) seems to rule in accordance with the Rambam and the Raavad.  In practice, the stricter opinion is followed (Aruch Hashulchan 201:9).  For a conceptual analysis of this dispute and its implication for a different dispute, see Biurei Hagra Y.D. 201:91.

There is much discussion regarding the equivalence of forty Saah in liters.  The opinions range from 648 liters to 964.3 liters (for a complete discussion of this issue see Rav Yirmiyah Katz’s Mikva Mayim 3:50-59).  Rav Moshe Heinemann stated in a Shiur delivered to the Council of Young Israel Rabbis that common practice is to assume that forty Saah is the equivalent of a minimum one thousand liters in order to avoid all doubts.  Recall our previous issue, where we noted the common practice to be exceedingly stringent regarding Hilchot Mikvaot.

There are a number of other possible differences between a Mikva and a Maayan.  The concern of “Natan Saah Venatal Saah” (a very relevant issue that we will discuss in later issues) might not apply to a Maayan (Dagul Meirvava, commenting on Shach Y.D.201:63, Teshuvot Beit Shlomo Y.D. 2:59, and Teshuvot Maharsham 1:44) and the concern of discoloration of the water might not apply to a Maayan (Shulchan Aruch 201:28 and Pitchei Teshuva Y.D. 201:20).  Moreover, the concern for “Mayim Sheuvim” does not apply to a Maayan according to most Rishonim (see Shulchan Aruch Y.D. 201:15 and Aruch Hashulchan Y.D. 201:106-110).  Indeed, it was common in the time of the Rishonim to use Maayanot for Tevilah, because the use of Maayanot avoids many Halachic pitfalls (see Trumat Hadeshen 258).  Moreover, many Acharonim strongly encourage the use of a Maayan because of this reason (Teshuvot Sheialt Yaavetz 1:88, Lechem Vesimlah 201:3, and Teshuvot Arugat Habosem Yoreh Deah 210).  Indeed, some Chassidic groups currently have succeeded in creating places where one can immerse in a Maayan.  However, Rav Moshe Heinemann noted that this is not practical in most situations as the water in Maayanot is exceedingly cold and it is impossible to regulate the water level of the Maayan.  In addition, we should note that if the water in the Mikva is no longer attached to the Maayan, then (according to most opinions) the water no longer has the status of a Maayan, even thought the water was piped in from a Maayan (Shulchan Aruch Y.D. 201:10, Shach Y.D. 201:30, and Encyclopedia Talmudit 12:38-39).  Moreover, the Teshuvot Mishkenot Yaakov (Y.D. 43, cited in Pitchei Teshuva 201:28) severely limited the application of the rules of Maayanot, as he argued that most natural springs are not defined as a Halachic Maayan, since the springs are located too close to a river to be considered independent from the river.

Zochlin versus Ashboren

We are also extremely careful regarding the requirement that Mikva water be stationary.  The Rama (Y.D. 201:2) rules that a Mikva that is not stationary is disqualified on a biblical level (this is agreed to by virtually all authorities see Encyclopedia Talmudit 12:20-21).  Almost all Rishonim believe that the water need not be flowing in a torrent in order to be considered Zochlin.  Even water flowing through a crack in the wall of the Mikva is defined as Zochlin.   

 Many Rishonim believe, though, that in order to disqualify the Mikva, the water flow must be noticeable (Zechila Hanikeret).  The Rashba (Shaar Hamayim, Shaar 2) is often cited as the primary proponent of this view, but other Rishonim subscribe to this view (see Encyclopedia Talmudit 12:25).  The Shulchan Aruch (Y.D. 201:51) rules in accordance with this view.  The Acharonim subsequently debate how to define and quantify what is a Zechila Hanikeret and there is quite a wide range of opinions on this matter (see Encyclopedia Talmudit 12:25-26 and Mikva Mayim 2:23-31).

However, the Vina Gaon (Biur Hagra 201:96) appears to rule that even an indiscernible water flow (Zechila Sheeina Nikeret) disqualifies a Mikva.  Rav Chaim Soloveitchik (cited by Rav Yosef Dov Soloveitchik and Rav Moshe Shternbuch, Teshuvot Vehanhagot 1:513) vigorously supports this view.  In practice, Halachic authorities urge Mikva administrators to strive (at least Lechatchilah) that there not be even a Zechila Sheeina Nikeret in a Mikva (Rav Yitzchak Elchanan Spektor, Teshuvot Ein Yitzchak Y.D. 22 and Rav Chaim Ozer Grodzinsky, Teshuvot Achiezer 4:40).  Rav Moshe Feinstein (Teshuvot Igrot Moshe 3:63) also instructs that, Lechatchilah, there should not be even a Zechila Sheeina Nikeret in the Mikva.  Indeed, my cousin Rav Yosef Singer reports that regarding the Mikva in the Lower East Side, Rav Moshe was very particular that there not be even a Zechila Sheeinah Nikeret.  Rav Yirmiyah Katz (Mikva Mayim 2:31) notes that, practically speaking, a Zechila Sheeinah Nikeret eventually develops into a Zechila Hanikeret and thus should not be ignored.  

In fact, the care begins with the construction of the Mikva.  This was the motivation for the change made in the early twentieth century to use concrete in Mikva construction.  Previously, Mikva walls were lined with clay or stone (Mikva Mayim 1:139).   However, concrete was introduced to because it reduces concern for Zechila (Mikva Mayim 3:40).  Rav Katz (ibid.) advises that Mikva builders should pour the concrete for the floor and walls simultaneously in order to strengthen the foundation and further reduce concern for Zechila.  Indeed, part of the practical engineering expertise and experience required for building Mikvaot today is the creation of Mikvaot in a manner that avoids Zechila problems from the start. 

We should note that there was some debate regarding the Halachic propriety of using concrete in the creation of a Mikva.  However, it quickly became the universal practice to use concrete in the creation of Mikvaot (see Teshuvot Maharsham 2:102 – this is the most oft-cited responsum in this regard –Teshuvot Imrei Yosher 1:99, Teshuvot Doveiev Meisharim 3:87, and Teshuvot Divrei Yoel Y.D. 77:7). 

Rav Moshe Feinstein writes (Teshuvot Igrot Moshe Y.D. 2:89) that a Mikva must be periodically inspected for Zechila problems.  Rav Katz (Mikveh Mayim 3:133) notes that that there is no specific timeframe presented by Poskim for how often one should check a Mikva for Zechila.  He surmises that it depends on the age and condition of the structure, as an older structure probably requires frequent inspections.  Rav Katz notes that the process of checking for Zechila involves marking the water level of the Mikva and then closing it for a day and then inspecting the water level to see if it has fallen.  Interestingly, Rav Yosef Singer told me that Rav Moshe Feinstein used to check the Lower East Side Mikva for Zechila every Tisha Beav.  This way no one would have to delay his immersion.  Rav Katz told this author that this is the standard practice in  Mikvaot throughout the world.

Concern for Zechila is a major issue regarding the use of filters in a Mikva.  Rav Katz noted in a speech before the Council of Young Israel rabbis that Mikvaot in Israel do not use a filter due to this concern.  In this country, though, filters are commonly used, and special care must be taken to be sure that Zechila concerns are scrupulously addressed.  Indeed, Rav Yosef Singer told me that the Mikva in the Lower East Side uses a filter (as do almost all Mikvaot in this country), but that Rav Moshe Feinstein was not pleased that it needed to be installed.  Rav Moshe did not want to discourage anyone from immersing, so he agreed to the installation of the filter.  For a thorough discussion of the use of filters in a Mikva, see Rav Katz’s Mikva Mayim (2:66:-84).

It is interesting to note that in previous generations Mikvaot were built with drains on the bottom, despite the serious risk of the drains creating a Zechila.  This is because this was the only practical option for removing the water from the Mikva (see Teshuvot Chavatzelet Hasharon 1:Y.D. 68).  However, with the advent of pumping machines in the twentieth century, it became accepted to construct Mikvaot without drains (see Teshuvot Divrei Yoel Y.D. 76 and Teshuvot Mahari Shteif 71).  This is a beautiful example of modernity serving to enhance our devotion and fidelity to our precious Torah.

Rivers, Streams, Oceans, and Lakes

We mentioned that one may immerse in a spring even if it is flowing but that we are prohibited from immersing in a collection of rainwater (Mikva) if the water is flowing.  The Amoraim and Rishonim, though, debate the status of a river.  Many rivers consist of a combination of rainwater and underground springs.  The question, accordingly, is whether we regard rivers as a Mikva and they are thus disqualified for immersion because they are not stationary or do we regard them as Maayanot and are acceptable even though they flow.  This debate has never fully been resolved.  Shmuel (Shabbat 65b) adopts a very straightforward approach.  If the majority of the river consists of rainwater, then the river is regarded as a Mikva.  If the majority of the river is from underground springs then its status is that of a Maayan.  The drought of last year was apparent in the rivers, as they appeared significantly lower than normal.  The impact of the rain (or lack thereof) on the rivers was quite evident.

On the other hand, Shmuel is quoted (ibid.) as adopting a contradictory view.  He is quoted as saying a somewhat enigmatic statement “Nahara Mikipei Mivrach.”  Tosafot (ibid. s.v.Deamar Shmuel) explains that Shmuel means that the primary source of a river is its underground sources.  Tosafot explain based on the Gemara (Taanit 25b) that for every handbreadth of rain that falls into the river, another two handbreadths of water emerge from the underground water sources.  This version of Shmuel believes that all rivers are defined as a Maayan.  The Rama (Hilchot Mikvaot 201:2), though, cautions that even this opinion concedes that if the river consists entirely of rainwater then it is not a Maayan.  If a river or stream dries up completely when there is a drought, then it is obvious, notes the Rama, that this river is simply a flow of rainwater (Chardalit Shel Geshamim), which all Rishonim agree is not a Maayan (see Mikvaot 5:6).

The Rishonim debate which opinion to follow.  Most Rishonim follow the stricter approach of Shmuel to follow the majority of the rivers’ water content.  These Rishonim include the Rambam (Hilchot Mikvaot 9:13), the Tur (Y.D.201), and the Ramban (in his commentary to Shabbat 65b).  Tosafot (ibid.), however, cite Rabbeinu Tam who rules in accordance with the lenient version of Shmuel.  Tosafot conclude “it is upon this we rely to immerse in rivers, even if they are quite swollen.”  Rav Yosef Karo (Shulchan Aruch Y.D. 201:2) rules in accordance with the stricter opinion.  The Rama (ibid.), though, records the practice to immerse in rivers when a community is far from a Mikva.  The Rama concludes that it is quite preferable to follow the strict opinion, but that one should not admonish those who follow the lenient opinion.  The Aruch Hashulchan (Y.D. 201:42) notes that in the late nineteenth century the practice of those who live at a great distance from a Mikva was to immerse in a river. 

Today, with the advent of modern means of travel, Poskim rarely, if ever, sanction the use of a river for immersion.  Moreover, Rav Yirmiyah Katz told the National Council of Young Israel rabbis that he has made small Mikvaot in individuals’ backyards and garages in places such as Eugene, Oregon, which are far from centers of Orthodox Jewish life, for less than twenty thousand dollars.  A Rav perhaps might sanction an Ashkenazic Jew relying on a river for Tevilat Keilim in case of great need such as for Baalei Teshuva visiting a parent who lives very far from a Mikva.  It is, however, preferable to use a spring or still lake in such a circumstance if it is practical to do so. 

Finally, the Tannaim debate the status of oceans (Mikvaot 5:4), whether they are acceptable for immersion despite the fact that they are Zochlin.  The Shulchan Aruch (Y.D. 201:1) reflects the accepted view among the Rishonim that the Halacha follows the opinion of Rabbi Yose who considers oceans to be acceptable for immersion.  The Aruch Hashulchan (Y.D. 201:42) adds that lakes are acceptable for immersion even if they become completely dry during a drought, if its waters are still.


It is incredibly challenging to create and maintain a Kosher Mikva.  A Mikva can easily become disqualified in the absence of competent and vigilant creation and maintenance.  We will continue discussing this topic with a special attention how the laws of Mikvaot are applied and even enhanced in the modern context.

The Building and Maintenance of Mikvaot – Part Three by Rabbi Chaim Jachter

The Building and Maintenance of Mikvaot – Part 1 by Rabbi Chaim Jachter