What constitutes a kosher mikvah? The word mikvah means gathering of
waters. We first encounter the term in the Torah on the third day of creation,
when G-d creates the land and sea. Let the waters be gathered together
(yikavu hamayim)
and the gathering of waters (mikveh
hamayim) He called seas. (Gen.1:9-10) According to Rashi**, this
primordial mikvah was the Mediterranean Sea.
The waters of a mikvah must
gather together naturally. One may not just use tap water. They must come either
from an underground spring or from rainwater; which may then be joined with tap
water. If spring water is used, then the water can be flowing. However if the
source is rainwater, then the water must be stationary. The ocean,
halachically, is considered a spring. Thus, even though the water is
flowing, it can still be considered a kosher mikvah. Rivers and lakes are more
complicated, because the source could be either rain or spring water. If the
river dries up during a drought, then its source is rainwater. Since a mikvah
which comes from rainwater must not be flowing, therefore such a river would not
be kosher. A river which does not dry up could probably be used as a mikvah.
If a woman is actually in a situation where she needs to use the ocean or a
river as a mikvah, a competent Rabbi must be consulted. It is always preferable
to use a kosher man-made mikvah.
A mikvah must contain a minimum of
forty seah (around 750 liter or 198 gallons) of water. Our Sages have
determined that this is the minimum amount needed in order to immerse
comfortably. The forty seah corresponds to the forty days and nights
that the earth was covered in the waters of the Great Flood. Just as the earth
needed to be totally submerged for forty days in order to become cleansed and to
begin anew, so too a woman immerses herself in forty seah of water.
Forty seah is the minimum requirement. The height of the water is
usually about 1.2 m. (4 ft.) above floor level not too shallow and not too
deep.
**Rashi is the acronym for Rabbi Shlomo Yitzchaki, French scholar of 11th century France and primary exponent of the Talmud, the core of Judaisms vast intellectual heritage.
Reference: S.Z.Lesches, Understanding Mikvah : An Overview of Mikvah
Construction