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


This week we will explore one of the major challenges involved in creating a Kosher Mikva, the Mayim Sheuvim problem.  We will discuss the basic parameters of this issue and two ways of remedying water that we consider Mayim Sheuvim.

Mayim Sheuvim

In a previous issue, we saw the Torah’s (Vayikra 11:36) two ways of purification, immersion in a Maayan (natural spring) and immersion in a collection of rainwater in a pit (Mikva).  The Torat Kohanim (ad. loc.) states that just as Hashem places the water in a Maayan, so too the water in a Mikva must be placed there by God (i.e. without human intervention).  Accordingly, water that has been in a receptacle such as a bucket is disqualified for use in a Mikva.  If, for example, one drew water from a well with a bucket and placed the water in a hole in the ground, the water would be considered Mayim Sheuvim  (drawn water).  In the modern context, water from the tap is considered Mayim Sheuvim since (as explained by Rav Moshe Heinemann in a Shiur delivered to the Council of Young Israel rabbis) the water passes through receptacles in purification plants and water meters (also see Chazon Ish Y.D. 123:1).  For further discussion of this issue, see Aruch Hashulchan (Yoreh Deah 201:169), Rav Nissin Telushkin (Taharat Mayim chapter 40), and Rav Yirmiyah Katz (Mikva Mayim 3:93-95). 

Accordingly, the rainwater must reach the Mikva without ever having been in a receptacle.  We, therefore, pay careful attention that the pipes that bring the water to the Mikva should not constitute a receptacle.  The pipes should ideally be smooth without indentations (see Rama Y.D. 201:36 and Pitchei Teshuva 201:24).  Ideally, elbow pipes should be avoided as the Raavad (gloss to Rambam Hilchot Mikvaot 8:7) seems to believe that they constitute a receptacle.  For a lengthy discussion of the practical aspects regarding pipes that are used to transport rain from the roof to the Mikva, see Rav Yirmiyah Katz, Mikva Mayim 3:142-218).

There is a wide range of opinions whether Mayim Sheuvim are disqualified on a Torah level or only a Rabbinic level.  Tosafot (Bava Batra 66 s.v. Michlal) discuss this issue at length.  They cite the Ri who believes that Mayim Sheuvim are disqualified only on a Rabbinic level, and Rabbeinu Tam who believes that if all or the majority of the water in the Mikva is Mayim Sheuvim, the Mikva is disqualified on a Torah level.  The Aruch Hashulchan (Y.D. 201:11-17) reviews the three other variations of these opinions that appear in the Rishonim.  The Rama (Y.D. 201:3) rules in accordance with Rabbeinu Tam.

A very basic rule is that the presence of at least three Logim of Mayim Sheuvim in a Mikva that does not have a minimum of forty Saah disqualifies a Mikva (Mikvaot 2:4).  Rav Heinemann stated that three Logim is the equivalent of less than one quart.  However, once there are forty Saah (which we assume is more than one thousand liters as we mentioned in a previous issue) of Kosher water in the Mikva, then any added Mayim Sheuvim  does not disqualify the Mikva (Mikvaot 2:3 and 6:8). 

We should note that there are a number of other ways for rainwater to become disqualified for use in a Mikva.  These include discoloration (Shinui Mareh), the water entering the Mikva via an item that is Mekabel Tumah (Havayato Al Yedei Tumah), and human involvement in its transportation to the Mikva (Tefisat Yedei Adam).  Rav Yirmiyah Katz thoroughly discusses these issues in his three-volume work, Mikva Mayim.

Correcting Mayim Sheuvim  – Hamshacha

                Once a Mikva has three Logim of Mayim Sheuvim before it has forty Saah of rainwater, the Mikva remains disqualified no matter how much Kosher rainwater is added to the Mikva.  Nevertheless, the Halacha provides for a number of ways to remedy the Mayim Sheuvim status of water that had been in a receptacle.  One way is the process of Hamshacha, running the Mayim Sheuvim along the ground.  The Gemara (Temura 12a) cites a Braita that teaches that if the Mikva has a base of more than twenty Saah of rainwater that went directly into the Mikva, then one may obtain the rest of the forty Saah by taking Mayim Sheuvim and running it along the ground on its way into the Mikva.  The Rambam (Hilchot Mikvaot 4:8) and Shulchan Aruch (Y.D. 201:44) codify this Braita as normative Halacha.  For a conceptual analysis of the process of Hamshacha, see Rav Yitzchak Zeev Soloveitchik in his commentary to Temurah 12b.  We should note that the Radbaz (Teshuvot 1:85) writes that this process is acceptable only Bdiaved (post facto) and should not be relied upon Lechatchilah (initially).  Rav Moshe Feinstein (Teshuvot Igrot Moshe Y.D.3:64:3) and Rav Yonatan Shteif (Teshuvot Mahari Shteif 142) rule in accordance with the Radbaz.

There are a number of major disputes that pertain to the process of Hamshacha.  One debate is the status of a Mikva that is created entirely through the process of Hamshacha.  The Rambam (Hilchot Mikvaot 4:9) cites an anonymous “few sages from the West” who believe that a Mikva is acceptable even on a Rabbinical level even if the entire Mikva was created through the process of Hamshachah.  Some argue that the Rif and Rashi subscribe to this view.  The Rambam strongly rejects this view.  The Chazon Ish (Y.D.130:14) writes that he believes that the Raavad believes that a Mikva is disqualified on a Torah level if all of its water entered via Hamshacha.  Tosafot (ibid.) suggest an intermediate position that a Mikva whose water entirely consists of Mayim Sheuvim revitalized through Hamshacha is only disqualified on a Rabbinic level.  Many (but not all) later authorities adopted this approach.  These authorities include Teshuvot Tashbeitz (3:12), Teshuvot Maharit (Y.D.2:17), Teshuvot Divrei Chaim (introduction to Hilchot Mikvaot, number 5), Yeshuot Yaakov (201:15), and Chazon Ish (Y.D. 126:1 and 130:14). 

The second debate regards how much area of land must the water roll across in order to qualify as Hamshacha.  The Beit Yosef (Y.D.201) cites a debate among the Rishonim whether the water must roll along three Tephachim of ground (three handbreadths, which is the equivalent to approximately nine to twelve inches) or perhaps even a tiny bit of land suffices.  The Shulchan Aruch (Y.D. 210:45) rules in accordance with the strict opinion that three Tephachim are required.  We should note that the Chazon Ish (Y.D. 126:6) rules that the three Tephachim for Hamshacha need not be straight.  He believes that even if the Hamshacha area bends it is acceptable.  This seems to be the commonly accepted approach.

A third debate is what sort of ground is acceptable for Hamshacha.  The Shulchan Aruch (Y.D.201:46) rules in accordance with the majority of Rishonim that any surface is acceptable for Hamshacha.  The Rama (ibid.), though, rules that it is proper to follow the strict opinion of the Mordechai that the surface used for Hamshacha must be suitable to absorb water.  Early twentieth century authorities debate whether cement is considered a surface that is suitable for absorption since dirt is a major component of cement.  Rav Meir Arik (Teshuvot Imrei Yosher 2:67 and 85) rules that it is not suitable for absorption and the Chazon Ish (Y.D. 123:1) and Teshuvot Maharshag (2:6) rule that cement is suitable for absorption.  This view is accepted in practice, as noted by Rav Shlomo Dichovsky (Techumin 16:117).  Rav Yirmiyah Katz (Mikva Mayim 3:228) notes that some adopt a compromise view and use cement that has an unusually high concentration of dirt in an attempt to satisfy the strict opinion.

We should note that currently, most Mikvaot employ the process of Hamshacha as a means of ensuring the Kashrut of the Mikva, as noted by Rav Shlomo Dichovsky (Techumin 16:117).  Thus any water that enters any part of the Mikva enters by Hamshacha.  In this manner, we immediately reduce the concern of the Kashrut of the water from a Torah level problem to only a Rabbinic  level problem, as recommended by Rav Moshe Feinstein (Teshuvot Igrot Moshe Y.D. 1:119) and others including Teshuvot Beit Yitzchak (Y.D. 2:27:4) and Teshuvot Maharsham 1:145.  We subsequently solve the Rabbinic level problem by the use of Hashakah and Zeriah, which we will now begin to discuss.


In the times of the Gemara (see Shabbat 14a) it was common for people to use pits filled with rainwater that were located in caves as Mikvaot.  After a short while, however, these Mikvaot became dirty and difficult to use.  In fact, the people used to bathe to clean themselves after immersing in the Mikva, a practice that the Rabbis did not approve.  In later generations, people often immersed in springs, where there was no concern for the cleanliness of the water.  There were, however, some very significant problems associated with immersing in springs, such as its very cold temperatures, that make the use of springs impractical on a community-wide level.  In the past few centuries, almost all Mikvaot are designed to have the people immerse in water that is changed regularly.  In most Mikvaot, the water enters the immersion pit as Mayim Sheuvim but has its status of Mayim Sheuvim remedied by the process of Hashakah.

Hashakah involves two bodies of water that touch each other.  This involves filling one pool with Kosher rainwater (with all the great care involved in collecting and transporting this water) and another pool with water from the tap that is considered Mayim Sheuvim.  People immerse in the pool filled with tap water and no one immerses in the pool filled with rainwater (the rainwater pool is covered to preserve the water and maintain its cleanliness).  The tap water is changed periodically to ensure a high level of cleanliness.  The two pools are constructed in immediate proximity to each other and a common wall separates the two pools.  The tap water is rendered Kosher by its contact with the rainwater through a hole in the common wall that separates the two pools.  The Mishna (Mikvaot 6:7) records that the Torah level mandated size of the hole is Kishfoferet Hanod (the opening of a container).  The Mishna explains that this is an area in which two fingers can fit comfortably.  Twentieth-century Rabbinic authorities debate the equivalence of this Shiur in inches.  The opinions range from one and a half inches (Rav Avraham Chaim Naeh, Shiurei Mikva p. 163) to three inches (Rav Moshe Feinstein, Teshuvot Igrot Moshe Y.D. 2:89). 

The tapwater in the Mikva must reach the height of the hole between the two Mikvaot.  The wall of the pool in which people immerse usually has two colors of tile.  The tiles below the hole are of one color and the tiles above the hole are of another color, so that if the water in the pool is below the required level of the hole, it should noticeable and obvious (Mikva Mayim 3:107).  Rav Katz spoke at the Council of Young Israel rabbis of the serious risk involved in not employing this precaution.    

                There is a major dispute among the Rishonim whether the hole that creates the connection between the Kosher water and the Mayim Sheuvim must exist at the time of immersion or whether it suffices for the two waters to have come into contact once.  The Rosh (Teshuvot 31:2) is often cited as the primary proponent of the lenient view and Rabbeinu Yerucham (26:5) cites an opinion that adopts the stringent view.  The Shulchan Aruch (Y.D. 201:52) rules in accordance with the lenient view of the Rosh but the Shach (Y.D. 201:112) concludes that it is best to accommodate the stricter opinion.  Most Mikvaot today follow the strict opinion as many Acharonim urge that we follow the strict opinion (Teshuvot Beit Shlomo Y.D.2:62, Teshuvot Divrei Malkiel 2:66, and Teshuvot Maharsham 3:249).  For a conceptual analysis of this dispute, see Rav Chaim Soloveitchik (commentary to the Talmud, Mikvaot 1:7).

We should note that in most Mikvaot, both the tap water that enters the immersion pool and the rainwater that enters the storage pool undergo the process of Hamshacha before entering the pool.  Thus, the water is kosher by both the process of Hamshacha and the process of Hashakah.  Hamshacha first reduces the Mayim Sheuvim problem to a Rabbinic level prohibition and then the Hashakah renders the water as Kosher for immersion.  We should note that Hashakah alone suffices to Kasher the Mayim Sheuvim , but we add the Hamshachah process for an added measure of safety.  In this way, even if a mistake is somehow made with the Hashakah, the water used for immersion is disqualified only on a Rabbinic level.  Even the rainwater that enters the storage pool first undergoes Hamshacha as a safety precaution in case of a Halachic failure in the piping and the transportation of the rainwater from the roof to the storage pool.


Rav Yirmiyah Katz graciously permitted Kol Torah to reprint the illustrations of Hashakah and Hamshacha from his Mikva Mayim.  We hope the diagrams enhance and clarify our discussions.  In the next issue, with Hashem’s help, we will discuss, Bli Neder, a third manner of Kashering Mayim Sheuvim  – the process commonly refered to as Zeriah.

Unspoken Bond by Rabbi Avi Pollak

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