The Building and Maintenance of Mikvaot - Part Four by Rabbi Chaim Jachter


In our last issue, we discussed how contemporary Mikvaot are created.  We explained that people immerse in a pool filled with tap water, which fundamentally is unsuitable for immersion.  We render the tap water (Mayim Sheuvim) as Kosher for immersion in a number of ways.  The first is Hamshacha, running the water along the ground before it enters the Mikva.  Second, is the process of Hashakah, in which the tap water in the immersion pool touches water of an adjacent pool that contains rainwater through a hole that is made through the common wall of the two pools (consult the illustration in our last issue for clarification).  This week we will discuss a third option how to render Mayim Sheuvim suitable for immersion, the process of what we commonly refer to as Zeria.

The Process of Zeria

The Mishna (Mikvaot 6:8) describes the following situation.  There are two pits along a mountainside, one above the other.  The top pit contains the required volume of rainwater (forty Saah or one thousand liters) and the bottom pit is empty.  The Mishna teaches that there is a way to fill the bottom pit with water that is suitable for immersion without having to wait for rain.  The process is to bring water in buckets and pour it into the top Mikva and the resulting overflow will fill the bottom Mikva with water that is Kosher for immersion.  Recall from our previous issue, that once a Mikva contains the requisite amount of rainwater, one may add an unlimited amount of Mayim Sheuvim to the Mikva and the Mikva remains Kosher.  Moreover, the added water is Halachically transformed thereby from Mayim Sheuvim to water that is suitable for immersion.  Thus, the Mayim Sheuvim that is poured into the top Mikva is rendered Kosher by its contact with the rainwater in the pit and then by the force of gravity the water flows and fills the bottom Mikva.  The result is two Kosher Mikvaot along the mountainside.

Most Mikvaot today employ this process in the following manner.  A pit is made to hold rainwater on the side of the pool that will be filled with tap water.  After the pit is full with at least forty Saah of rainwater, we run the tap water through this pit and the water flows into the adjacent immersion pool (see diagram for clarification) through a hole in the common wall.  The tap water is rendered Kosher by its placement into the rainwater pit and emerges into the immersion pool as Kosher water.  When the water in the immersion pool needs to be changed for health and aesthetic considerations, the water is removed from the immersion pool and the process of Zeria is repeated.  We refer to this process as Zeria (which literally means planting), because we are “planting” the unsuitable water into suitable water, thereby giving the Mayim Sheuvim a new status, just as a seed achieves a new status when it is planted in the ground. 

Zeria versus Hashakah

The process of Zeria differs quite significantly from Hashakah.  In the process of Hashakah, the water enters the immersion pool as disqualified water and is subsequently rendered Kosher by its contact with the water from the pool containing rainwater (Bor Hashakah).  On the other hand, in the process of Zeria, the water is rendered suitable for immersion before it enters the pool.

The Chatam Sofer (cited in Pitchei Teshuva Yoreh Deah 201:24) and the Chazon Ish (Y.D. 123:1-5) were the most vigorous proponents of the use of Zeria to make water Kosher for use for immersion.  In fact, the norm in pre-war Hungary was to use only the process of Zeria to render the water Kosher for immersion.  Similarly, Mikvaot built in Bnei Brak and elsewhere in Israel under the supervision of the Chazon Ish operate with the Zeria system of making water Kosher and not Hashakah.  Interestingly, this phenomenon seems to have ancient roots.  In an essay published in Techumin (17:389-398), Asher Grossberg seeks to demonstrate from archeological evidence that the ancient Mikva at Massada operated solely with the Zeria system. 

Problems with Zeria

There are three potential problems that arise with creating a Mikva exclusively through Zeria.  The first is that the water enters the Mikva as Kosher and is not subsequently rendered Kosher.  This can pose a problem because (as we discussed in our previous issue at length) if there are three Logim (a bit less than a quart) of Mayim Sheuvim in the Mikva before there are forty Saah of Kosher water in the Mikva, the Mikva remains disqualified no matter how much Kosher water is subsequently added to the Mikva.  Rav Katz (Mikva Mayim 1:43, 59-60) relates stories where more than three Logim of Mayim Sheuvim were unintentionally present in the Mikva before the Zeria procedure occurred and people subsequently immersed in the Mikva without knowing that it was not a proper immersion. 

Moreover, as today our practice is to use a pump to remove water from a Mikva when the water needs to be changed for hygienic reasons (as discussed in a previous issue), a new problem arises.  The pump cannot remove one hundred percent of the water from the Mikva as there is some backwash of water that enters the pump, then leaves the pump, and returns to the Mikva.  This poses a very serious problem because there are receptacles in the pump that render the water Mayim Sheuvim.  Thus, the water that emerges from the pump and reenters the Mikva in the backwash is Mayim Sheuvim (see Teshuvot Minchat Yitzchak 5:90 and Teshuvot Chelkat Yaakov 3:54).  Hence, the Mikva must be dried thoroughly by hand so that three Logim of Mayim Sheuvim do not remain in the Mikva.  If three Logim of Mayim Sheuvim remain in the Mikva as the new water enters the Mikva, the water is unsuitable for immersion. 

This is a primary motivation for most Mikvaot to employ both the processes of Zeria and Hashakah to render a Mikva as Kosher.  If either process fails, then the other process serves as a backup.  Rav Avrahan Chaim Naeh (Shiurei Mikva p.167) notes that the accepted practice in Jerusalem is to employ both the process of Zeria and Hashakah.  Rav Moshe Feinstein (Teshuvot Igrot Moshe Y.D. 1:111), similarly urges that both Hashakah and Zeria be used whenever possible.  Moreover, Hamshachah is also used in most Mikvaot to make the water Kosher (as mentioned in our previous issue) in order to provide even further insurance of the Kashrut of the Mikva.  This recalls the Pasukim in Kohelet (4:9-12) that teach, “two is better than one…and a threefold cord is not quickly broken.”

Zeria Bezochlin

A second challenge involved with Zeria is a problem described by the Acharonim as “Zeria Bezochlin.”  Recall that a Mikva is not Kosher if the water in the Mikva is flowing out of the Mikva (into a hole or crack etc.).  Accordingly, a number of Acharonim (Chazon Ish Y.D. 123:1, Teshuvot Maharam Schick Y.D. 198, and Teshuvot Maharsham 1:122 and 145) ask how can Zeria be effective if the water flows out of the Bor Zeria during the time the Zeria process occurs.  If a Mikva is disqualified if its water is flowing out, then how can a Bor Zeria make Kosher tap water that is placed into it, when the water is flowing out of the Bor Zeria?

There are a number of ways to address this problem and different Mikvaot have adopted the various approaches.  First, the Chazon Ish (ibid.) writes the problem is mitigated by the fact that the city water is made Kosher by Hamshacha even before it enters the Bor Zeria.  As we discussed in a previous issue, this reduces the severity of the issue from a Torah level problem to a Rabbinic level problem, since most Rishonim believe that Mayim Sheuvim that has undergone Hashachah, is acceptable on a Torah level.  Second, some Acharonim (Teshuvot Imrei Yosher 1:94 and 2:73, Teshuvot Chelkat Yoav Y.D.1:32 and 2:17, and Teshuvot Igrot Moshe Y.D. 1:112) believe that the problem does not exist altogether and that it is acceptable for the Bor Zeria to be flowing during the Zeria process.  Rav Moshe explains that Zochlin does not disqualify a Mikveh per se; rather, the individual has not properly immersed if the water is flowing out of the Mikva.  Accordingly, water in a Bor Zeria can make city water Kosher even if water is flowing out of it.  Rav Moshe cites the aforementioned Mishna in Mikvaot as proof to his approach.

A third approach (suggested by Rav Yaakov Landa, the famed Rav of Bnei Brak, cited in Rav Telushkin’s Taharat Mayim p. 184) is to close the hole through which the water flows from the Bor Zeria into the immersion pool during the Zeria process.  In this manner, the water in the Bor Zeria is not considered Zochlin during the Zeria process.  After the Zeria process is finished then the hole is opened and the excess water from the Bor Zeria will flow into the immersion pool.  Aside from practical concerns (the Bor Zeria will have to be constructed with the potential to contain an enormous volume of water), there are some who criticize this method from a Halachic perspective.  They express concern that the water in the immersion pool enters because of Tefisat Yedei Adam (human intervention – the opening of the hole leading from the Bor Zeria to the immersion pool).  For a summary of the rich literature that debates this issue, see Mikva Mayim (1:27-33). 

The most commonly employed approach to resolve this problem is the method suggested by the Chazon Ish.  He writes that one should construct the hole on the lower portion of the wall where the city water enters the Bor Zeria and the hole on the top of the wall where the water flows from the Bor Zeria into the immersion pool.  In this manner, the city water enters a part of the Mikva that is not Zochlin.  Rav Yaakov Breisch writes (Teshuvot Chelkat Ya’akov 3:53:2) that he employed this method when constructing the Mikva in Zurich in 1959 and Dayan Weisz writes (Teshuvot Minchat Yitzchak 2:23) that this is the method that he used when building the Mikva in Manchester in 1957.  Others criticize this approach and ask how part of the Mikva can be considered Zochlin and another part not considered Zochlin.  See Rav Katz (ibid.) for a review of this issue.


Natan Saah Vental Saah

A third problem associated with the process of Zeria is the celebrated problem of Natan Saah Venatal Saah.  The Mishna (Mikvaot 7:2) writes that if one has a Mikva that contains exactly forty Saah and adds a Saah of fruit juice (but does not change the color of the Mikva) and subsequently removes a Saah of the rainwater (Natan Saah Venatal Saah), the Mikva remains Kosher.  The Gemara (Yevamot 82b) limits this leniency to a situation where a minimum of more than twenty Saah of rainwater remains in the Mikva.  Most Rishonim (including Rashi, Tosafot, Rosh, Ramban, Rashba, and Ritva to Yevamot 82b and the Rash to Mikvaot 7:2) believe that this limitation applies only to fruit juice and not to Mayim Sheuvim.  However, the Rambam (Hilchot Mikvaot 4:7) and the Raavad (Baalei Hanefesh, Shaar Hamayim) rule that this limitation applies even to Mayim Sheuvim.  According to the Rambam and the Raavad it appears that at least twenty Saah of the original rainwater must remain in the Mikva in order for it to be suitable to make Mayim Sheuvim Kosher (also see the analysis of the Rambam and Raavad by the Chazon Ish, Y.D.123:1-3). 

The Shulchan Aruch (Y.D. 201:24) and most of its commentaries rule in accordance with the lenient opinion advocated by the majority of Rishonim.  The Shach (201:63), though, cites the Tashbetz who concludes that we must accommodate the strict opinion of the Rambam and Raavad.  This poses a serious problem to the process of Zeria, as when Zeria is employed repeatedly the original rainwater will not remain in the Bor Zeria.  This is yet another reason why most Mikvaot employ the processes of both Zeria and Hashakah (see, for example, Rav Moshe Feinstein Teshuvot Igrot Moshe Y.D.1:111).  Rav Moshe and the Jerusalem custom assume that the use of a Bor Hashakah satisfies even the opinion of the Rambam and Raavad.  The Chazon Ish, though, vigorously argues that the original rainwater does not remain even in a Bor Hashakah and is unacceptable according to the Raavad.  Although it takes longer than a Bor Zeria to lose the original rainwater, the Chazon Ish believes that the waters in the immersion pool and the Bor Hashakah easily mix and soon the original rainwater in the Bor Hashakah will be lost.  Hence, the Chazon Ish felt that there is no benefit to employ both Hashakah and Zeria.  Rather, Zeria coupled with Hamshachah suffices in his view.


Most Mikvaot employ Zeria, Hashakah, and Hamshacha to ensure the Kashrut of the Mikva.  The Chatam Sofer and Chazon Ish, though, felt that Zeria without Hashakah suffices.  An oral tradition explaining why the Chazon Ish strongly opposed using Hashakah appears in Rav Katzs’ Mikva Mayim (1:43).  Again, we thank Rav Katz for graciously permitting us to reprint illustrations from his Sefer to help clarify the concepts we have discussed in this essay.

The Building and Maintenance of Mikva’ot - Part Five by Rabbi Chaim Jachter

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