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7 Nissan 5760 - April 12, 2000 | Mordecai Plaut, director Published Weekly








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Building a Mikva In South Africa

by Aryeh Taback

It is only in the last few hundred years that manmade mikvas have become so prevalent all over the world. In dry areas such as Eretz Yisroel there was an ancient need to build suitable mikvas but elsewhere, where public water is more common, those needing immersion just used a natural spring or gathering of water suitable for the purpose.

The first documented outline for the construction of a mikva comes from the times of the Rishonim (11th To 15th century). One of the oldest in Europe is found in Cologne, Germany, dating to 1170 (4930).

In those times, many mikvas were built as follows: A wide shaft was dug into the ground to below the depth of the natural water table. The bottom of the shaft would then fill with water as the natural underground water seeped in through the walls and floor. Steps were then hewn into the side of the shaft, often in a spiral, from the ground level to below the water level. A person requiring immersion would descend into this "well" and immerse there. A mikva in Friedburg, Germany, went down more than 60 feet (18 meters)!

In the last few centuries a new type of mikva was constructed, one that is situated above or level with the ground surface yet which remains faithful to all the laws governing the underground version. Up until a few decades ago these mikvas were filled by gathering rainwater and directing it into the required pool. With the advent of modern boring and pumping techniques it has now become possible to fill these above ground mikvas with the natural water found underground.


A mikva is a collection of 40 se'ah -- the greater part of 1000 liters -- of suitable static water. Water is not suitable if it:

1) Has been contained in or passed through a container not built into the ground; or

2) Was propelled into the mikva by direct human energy.

There are many other laws and details pertaining to the suitability of water and the construction of the pool, but here we will focus only on these aspects, and how they were dealt with in the "Be'er Chaya Esther" mikva recently dedicated in Johannesburg, South Africa, where halachic aspects were supervised by HaRav Meir Posen. Of course, anyone actually wishing to construct a mikva should consult with a competent authority and not rely on what is written here for practical advice or recommendations since there are often special considerations that apply in a given instance.

The Modern Day Mikva

The water for the modern day mikva is obtained either by collecting rain water or by drilling for subterranean water. As we will see later on, once we have a kosher mikva from one of these two sources it is possible to combine tap water with either of them, but only according to certain strict guidelines.

When obtaining our initial water either from rain or a borehole, it is imperative that at no stage in the water's journey from its source to its destination does it violate either of the above two prerequisites. That is to say it must not at any stage pass through a container not built into the ground and it must also at no stage be propelled by direct human energy.

This is relatively simple when we are obtaining water from the rain, since the water can be gathered directly into a tank which was built into the ground and then piped directly into the mikva through straight pipes (which are not considered containers) using gravity to propel it from the gathering tank into the mikva. When obtaining water from a borehole, however, we run into some difficulties.

The Borehole Challenge

Water occurs naturally underground and is known as ground water. This water accumulates chiefly from the rain that filters through the soil. The water settles into the pores and cracks of underground rocks and into the spaces between grains of sand and pieces of gravel. A layer or bed of such porous material that yields useful amounts of water is called an aquifer. It is into this layer that a borehole is sunk.

The borehole usually takes the form of a long pipe which is inserted into a hole drilled into the ground by a boring drill, the end of this pipe being submerged in the aquifer. In most cases, where a mikva is not involved, the water is propelled up this pipe by attaching a pump to the bottom end of the pipe and pumping the water up. However, when it comes to building a mikva, this method of drawing the water up cannot be used because it violates both of the abovementioned requirements.

First, even though the pipes themselves are not considered containers, the pump is, and hence the water passes through a container which is not connected to the ground. Thus the water has violated our first prerequisite. Second, the water is being propelled by energy initiated by a person in the form of a pump and is not flowing naturally, thereby violating our second prerequisite.

The Borehole Solution

The modern-day solution to this vexing problem lies in a simple scientific phenomenon: a light liquid will rise to the surface of a heavier liquid, the most common example of this being oil and water. To illustrate how this relates to our borehole, suppose one were to place a straw filed with oil and plugged at the top, into a glass of water (Illustration A).

When the stopper is removed, one would observe that the water below the straw will force the oil in the straw upwards until some of the oil cascades out the top of the straw (Illustration B). This occurs because the oil within the straw is lighter than the water on the outside and hence needs to rise.

The same phenomenon would be observed if the straw were filled with carbonated water, because the carbonated water is saturated with gas and is, like the oil, lighter than the water around the straw.

Based on the above, we will now be able to understand how it is possible to draw up kosher mikva water from a borehole. The solution, which may sound more complicated than it is in practice, is to carbonate, or more accurately to aerate, the water in the pipe so that, like with the straw, the water below it will force the water in the pipe up to the surface. This is done by pumping compressed air from a powerful compressor (Illustration C) down a separate pipe to the base of the water pipe, and bubbling this air into the water in the pipe so that it gets aerated.

This method of raising the water satisfies both of our requirements for kosher water because, first, it does not pass through a container not built into the ground and second, because it spurts to the surface on its own accord and is not propelled by direct human energy. Only human ingenuity is at work here.

Building A Functional Mikva

Having obtained suitable rain or ground water, we can now simply direct it into an adequately-sized pool and we will have a perfectly kosher mikva. There is however a practical consideration to be dealt with, which obviously requires a solution which is in accordance with the halacha: Were we to use this single pool for the immersion itself, the water would become dirty after some time and would need to be replaced with either rain or borehole water, both of which are not always readily available in suitable quantities.

There are two ways to overcome this technicality, both of which are discussed extensively in the halachic texts. Both involve connecting a pool of fresh tap water to an existing kosher mikva in such a way that the new pool is rendered kosher by the existing mikva. The two possible methods of doing this are know as "Hashoka" (lit. "kissing") and "Zriah" (lit. "planting").


The Mishna in Mikvo'os (6: 7,8) describes how one can connect a mikva containing suitable water to one that is unsuitable by touching their water together and thereby make two kosher pools. The meeting point of the two waters needs to be a minimum size of "the spout of a waterskin" which was defined by the rabbis to be the width of the two fingers closest to the thumb squared, and is taken to be around 4.5 cm. squared.

Using this method we could fill the main mikva pool with clean -- even heated -- tap water and then simply allow it to touch (or "kiss") an existing kosher pool, known as the Bor Hashoka and thereby validate the fresh pool of water. This method allows us to keep one small pool of rain or borehole water indefinitely, only replacing the main pool at regular intervals with fresh tap water.


Once a mikva has the required 40 se'ah of water in it, the halacha states that one can add all the water in the world into this pool and it will not become unkosher. When using the Zriah method based on this halacha, a kosher mikva is built alongside an empty pool. Tap water is added into the kosher mikva until the mixture overflows into the empty pool. This second pool is used for immersions until gets dirty. It is then emptied and the entire process can then be repeated.

The process is named Zriah because one "plants" the unsuitable water in the mikva like a seed placed in the ground, and just as the grain becomes part of the ground so too the suitable water becomes part of the kosher mikva. The original kosher mikva in such a case is known as a Bor Zriah.

This method once again allows us to keep one small pool of rain or borehole water indefinitely, only refilling the main pool (by overflowing tap water from the smaller pool) at regular intervals.


The above two methods are described and endorsed by the Shulchan Oruch, the foremost authority when it comes to halacha. Under normal circumstances, we would follow the opinion of the Shulchan Oruch, even in the face of more strict opinions. The laws of mikva however are not normal circumstances, and about these laws the Tashbatz writes that we should try "not to poke ones head between a disagreement of the Rishonim." Thus one should rather take the strictest view into account, when practical, in order to satisfy all the opinions. It has been explained that the reason why one should be exceptionally particular when it comes to the laws of mikva, is because it is on these laws that the purity of the entire Jewish nation depends.

Other Opinions

There are two points about which some of the authorities differ with the Shulchan Oruch and have more stringent opinions. The first issue is one of dilution. All opinions agree that as long as we have 40 se'ah of kosher water, we can add all the water in the world into that pool and the pool would still remain kosher.

There is however one condition, according to some opinions. Supposing we had a kosher mikva containing exactly 40 se'ah. Into this pool we now add 80 se'ah of tap water. All opinions agree that this mixture is kosher. Now suppose someone removed a glass of water from this pool. The water in the glass would be composed of about two-thirds tap water and one-third mikva water. What we suddenly realize is that our original 40 se'ah now lacks a third of a glass, and the entire mixture becomes unsuitable. According to these opinions (which, as we said, the Shulchan Oruch does not follow), this problem undermines the entire concept of Zriah, where we completely ignored dilution and allowed the mixture to flow into the empty pool.

Even when using Hashoka, there can also be a problem of dilution. As someone enters the mikva, the water level rises and then drops and the motion of the water will slowly dilute the Bor Hashoka. When the main mikva is emptied, we may find that our Bor Hashoka contains less than 40 se'ah of kosher water.

As we mentioned already, and we want to stress this, this is a lone opinion -- primarily that of the Ra'avad -- which we would not usually take into account. The Shulchan Oruch's opinion on the above case would be that once we have added the tap water into the mikva, we view the mixture in its entirety and not as two separate components. Hence when one removes the glass of water according to the Shulchan Oruch, one has removed one glass of the kosher mixture and not two-thirds of a glass tap water and one-third kosher. Therefore, according to the Shulchan Oruch, Zriah is a perfectly valid way of filling the empty pool described above.

The second issue raised in the commentaries pertains to Hashoka and when it can or cannot be used. There are opinions which maintain that the mechanism of Hashoka was not created to purify an entirely unsuitable mikva as we proposed above but is rather a method of joining a kosher mikva which lacks the correct volume of water to one that has the volume.

Applying These Stringencies To A Real Mikva

Due to the above issues and based on the idea that we should take all opinions into account when building a mikva, various approaches are taken. In dry climates, two separate pools, an independent Bor Hashoka and Bor Zriah are used. This approach was discussed by the Chazon Ish.

Another approach, that was used in the "Be'er Chaya Esther" mikva that was officially opened in Johannesburg, South Africa last week, is to construct the mikva in such a way that we do not need to use tap water at any stage. The best way of doing this is to fill the immersion pool itself with borehole water. As an added stringency we also do a Hashoka between this pool and a smaller pool which was filled with rain water. This is done to counter the minute chance that the borehole was rendered unsuitable.

Rain water could also be used to fill the main pool but it is often dirty due to pollution in the atmosphere, and is not always available in suitable quantities. In some mikvas, they store rainwater and use some of it each time they refill the mikva.

It must be emphasized that we use these approaches only where possible and that a mikva is one hundred percent kosher if it was built as described in the Shulchan Oruch.

It is reported that the Chasam Sofer built a mikva relying entirely on Zriah and that this mikva was only filled with rain water once in its entire lifetime. Two mikvas were dug alongside one another, the one was then filled with rainwater and the other empty. Tap water was then introduced into the full pool until it overflowed into the empty one. One of the pools was then used for immersion until it became dirty, whereupon it was emptied and refilled by pouring tap water into its partner. After a short period of time, none of the original water would have remained, but this mikva was nevertheless perfectly kosher according to the Shulchan Oruch.

The Chasam Sofer's reason for building such a mikva was that the doctors in his town had recommended not to use the mikvas because they were supposedly detrimental to one's health. The Chasam Sofer knew that if he did not build mikvas containing the finest quality water, the spiritual purity of his entire town would be at stake. Hence he chose not to fulfill the chumros. He does however write that if one can be more stringent and use borehole water it is praiseworthy.

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