The links below will take you to subsections of this chapter.

I. What is Mikveh?
II. The quality of water required for a Mikveh
III. Qualifying unqualified water under extraordinary conditions
IV. The quantity of water required for a Mikveh
V. Requirements for the receptacle containing the water for Tevilah
VI. Public bathing places for Tevilah
VII. A bathtub is NOT a Mikveh

I. What is Mikvah?

The definition of the Hebrew term Mikvah is "an accumulation" of water. That term is usually applied to a ritual-font used for purification - the receptacle containing the Mikvah water. Tvilah is the act of complete immersion of a person in the Mikvah.

II.The quality of water required for a Mikvah

1. Any "natural" water, as a pool, pond, creek, stream, river, or lake, whether these waters originate from a spring or accumulate in a natural way from rain, melted ice, or snow, or the waters of the sea or ocean, are proper for immersion and purification from the state of Nidah, except that when a running stream is used for Tvilah, it must be ascertained that this stream originates from a spring. This can be established by investigation of the nature of the stream, to learn whether the flow stops after the rainy season and the water dies out. A stream composed of melted snow or rain water cannot be used for Tvilah unless the water is diverted to one side, making it still for the time being; or unless the stream or a part of it is dammed, making the water or a portion of it, for the time being, stationary. A completely watertight dam is not required, but simply a break - any kind of obstruction in the current. When a completely watertight obstruction is made, thus forming an enclosure separating the water therein from the stream, it must be ascertained that the portion of water amounts to at least forty se'ahs (twenty-four cubic feet), the required quantity for Mikvah, as hereinafter cited.

2. Water artificially accumulated is also proper for Mikvah, provided that such water is not drawn or conveyed by hand or by animal or man-power; or drawn or conveyed through such articles as may be called or classed as "vessels" or "utensils." Water which is drawn, carried, filled or conveyed by hand or by animal or man-power is not qualified to be used for Mikvah or Tvilah. Water which is drawn, carried, filled, or conveyed by or through an article or receptacle not attached to the ground, which article can be classed as a "utensil" or "vessel" is not qualified for Mikvah or Tvilah.

3. Articles (1) originally made to serve by attachment to the ground or building; and (2) which are neither made nor intended to hold water in themselves; and (3) which before they are assembled, attached, or connected are not capable of holding or/and retaining water in their regular position (by reason of a connection-opening in the lower part) - when they are properly assembled, connected, and permanently attached to the ground or building - are not considered as "vessels" or "utensils", and their identity as an article has ceased; it has passed into that of the building or ground, and is considered a part therof. And, when any water otherwise fit for Mikvah (as stated in Paragraphs 1 and 2, this section) has been drawn, carried, or conveyed by or through them, such water is proper for Mikvah. These are the fundamental rules. All other articles specified in sub-paragraphs following are subject to these conditions and must comply with them in order to be qualified; and, be it clearly understood that whenever we say of certain articles that they do not disqualify the water conveyed through them for mikvah, it is meant that those articles comply with these conditions. Therefore:

(a) Water pipes, coulings, fittings, or other waterwork contrivances, which are made to be laid in the ground, or attached thereto in a permanent manner, or to be attached to, or installed permanently in, a building for the purpose of conveying water, are not classed as "vessels" or "utensils"; and, it is proper to use the water conveyed by or through them for Mikvah.

(b) Water meters, sediment valves, shutoffs or faucets, which are made for the purpose of being permanently attached to the ground or building, or to the pipes which are attached to the ground and building, and are not classed as "vessels" or "utensils"; and they do not affect the propriety of the water conveyed by or through them, for the purpose of Mikvah.

Note: There has been discussion among some observant Jews about the qualification and the propriety of a water meter; whether or not it may be classed as a "vessel" or "utensil".

After listening to all the arguments, the author has by personal investigation found that those who raise this question are unfamiliar with the construction and mechanical principle of a water meter.

They assumed, or were led to believe, that the meter has a receptacle space, a place in which some water may be retained. This theory is in contradiction to the fact, which every one can investigate. There is no such thing as a space to receive or hold standing water in a meter; should that be the case, the water would hinder the working of the meter. In some makes of meters it may appear that the bottom drops a little below the pipe line, but that is only the outer casing. The inner parts must, necessarily, be in line with the inlet and outlet pipes.

Furthermore, should the bottom of the meter be lower than the pipe line, it would not matter; it would then be in the class of "a pipe which is narrow at each end and wide in the middle," which "is not considered as a receptacle," and is qualified to convey the water for a Mikvah (Yorah Deah, CCI.3-6).

But the fact remains that a meter is not meant to hold water; nor was it ever intended to hold water; and it does not hold water - any more than the rest of the piping system which the water passed through. It is made specifically to serve with the ground - to be attached to the pipes in the ground and the building. Before it is connected it is not capable of holding water. It complies fully with the fundamental conditions enumerated in Paragraph 3.

The rabbis, our great masters, in order to better understand the Torah, and be in a position to intelligently interpret it, have for that purpose studied other sciences in relation to the precepts - such as medicine, anatomy, embryology, astronomy, and mathematics. Manu of their accomplishments remain of great outstanding importance even today. Accordingly, any observant Jew and any student of Jewish law, who values the Torah, before discussing the validity of the water from a water supply for a Mikvah and the effect of the contrivances employed therein, as the meter, etc., must at least familiarize himself with the system of supply for the sake of the dignity of these holy precepts.

The author is by vocation a builder, practiced in construction and engineering, familiar with water-supply systems and their contrivances. He has on many occasions taken apart and thoroughly investigated water meters of different makes. And he 6nds that there is no space in the meter capable of retaining standing water; that there is no reason for questioning the qualiHcations of a water meter as a contrivance of the water system supplying water for Mikvah.

There is no justification for hesitating to use a Mikvah where the water is obtained from the regular water supply. It affords the best means for a proper Mikvah. Unfounded theories, dictated by excessive piety, do not help in upholding the cause of Tvilah. They only cloud the issue, inviting uncalled-for difficulties, raising obstacles, and creating pretexts for breaking the most holy command, woman's purification.

(c) Water tanks installed in the course of the supply of water, or on top of buildings, to regulate the supply or/and pressure, are not classed as "vessels" or "utensils" and do not disqualify the water conveyed by or through them for Mikvah; provided, however, that such tanks were originally made for that purpose, to be connected to the ground or building, and are in fact connected thereto and permanently installed; and provided, of course, that they have a hole in the very bottom (which is usually the case) as an outlet. A non-standard tank may be used for that purpose, providing it has a hole one and one-half inches in diameter in the bottom, before it is attached; and so constructed that all the water is drained away from the bottom.

(d) Water which goes through certain mechanical contrivances, for the purpose of heating, as a hot-water furnace heater, kitchen stove firebox piping, oil or gas coil heater, instantaneous gas or electric heater, or any other heating apparatus; or water which goes through an ordinary kitchen hot-water boiler or house hot-water storage tank; or water which passes through a circulating system of house-heating by radiation) is proper to be used for Mikvah; provided, however, of course, that each and any of these apparati is not capable of holding water in its regular position before being connected or attached, and is made originally tor that purpose; and is properly and permanently connected with the regular water system and with the building.

(e) It follows, therefore, that common house water, hot or cold, supplied by an ordinary water system for public use - water which as a rule originates from a spring, river, well, or rain, snow or/and ice sheds, is stored away in reservoirs, and then distributed through flumes, mains, side branch mains, and pipes, by means of gravity, power, or pressure, led into the home by means of pipes attached to the ground or building - is proper to be used for Mikvah, provided, however, that the water comes to the Mikvah in the same direct course, or through a rubber hose from the faucet to the Mikvah without any assistance of man while in the course of conveyance.

(f) Water from private water supplies, coming from an elevation by gravity, or pumped, raised, or conveyed by a windmill or any other power, to an elevated storage tank, and then led to the supply by permanent conveyances or pipings which are attached and/or connected to the structure, can be used for Mikvah; provided, however, that the storage tank complies with the constitutional rules in Paragraph 3 and further specified in division (c) this Section; and further, provided that the water is not raised, conveyed, or pumped by hand, or by animal or man-power.

4. If any water not qualified for Mikvah should happen to enter the Mikvah to an amount of three lugim (one quart U. S. A. standard measurement) before the Mikvah has been filled with the proper water to the full amount, forty se'ahs (twenty-four cubic feet), then the entire amount of water in the Mikvah becomes disqualified. In that case, all the water in the Mikvah must be completely drained - removed therefrom - and the Mikvah then refilled with the proper water.

III. Qualifying unqualified water under extraordinary conditions

1. In case of necessity, a Mikvah may be filled by hand with snow or natural ice. When melted, the water is proper for Tvilah.

2. Unqualified water may become qualified when brought in contact with water which is qualified. Therefore, in case of necessity, a Mikvah may be filled with any kind of water, or in any way, and a contact then made with a nearby spring, well, or other qualified waters, such as mentioned hereinbefore (Sec. II), and after the contact the Mikvah becomes qualified for Tvilah; provided, that when any water other than a spring is made use of to qualify unqualified water, the qualified water contains in itself the amount of water required for Mikvah (which is not less than forty se'ahs, twenty-four cubic feet).

3. In places where water is obtained under difficult conditions, as in undeveloped territories, arid districts, or deserts, a pit may be dug in the ground; or a receptacle may be built attached to the ground, or a ready-made receptacle may be set in the ground (subject, however, to the rules in Section V, this chapter), as a Mikvah, where rain-water or water from melted snow or ice may be permitted to drain on the ground or from the roofs, in its natural course, or by media attached to the ground or building, until the water automatically reaches the receptacle and fills it at least to the amount of over half of the volume of water required for a Mikvah, that Is, more than twelve cubic feet. The rest of the water to make up the full volume required may then be carried or brought from any other place and poured on the ground, not directly into the Mikvah, but at least one foot away, in such a manner that the water will seep or drain on the ground before it reaches the Mikvah. If the ground is very porous, the water may be drained on harder materials placed and attached to the ground, such as rock, brick, plaster, or concrete, but not on such materials or commodities as may be classed as "vessels" or "utensils."

4. When any such Mikvah becomes stagnant for want of a change of water, and there is no other qualified water available to take the place of the old water, another Mikvah may be constructed nearby and filled with any kind of water - even though it is not qualified for a Mikvah on its own merit - and a contact made with the Mikvah already qualified. When this is done, the water In the newly constructed Mikvah becomes qualified. Now, since there are two qualified Mikvahs, the first one, or either one, can be renovated merely hy emptying the old water and refilling it with fresh water, and bringing this water in contact with the water of the remaining proper Mikvah. Contact of the water in the two Mikvahs must be through a definite, direct opening or by a connected pipe. In the event that the two Mikvahs are not on the same level, care should be taken that immediately after the contact is made the opening be plugged or shut off, so that the Mikvah on the higher level shall not drain and become disqualified by losing its water below the minimum amount required. And, in any event, the water in any Mikvah must not run or drain at the time of immersion.

5. In the event that either of these two Mikvahs happens to lose its water below the amount required (twenty-four cubic feet) a contact may be made by an opening, or through a pipe not less than one and one-half inches in diameter, or their equivalent. When these Mikvahs are thus connected, the volume of water in the two of them is considered as if it were in one, because of the contact. And if there are forty se'ahs of water in all, Tvilah may be performed in either of them, provided, however, the depth of the water in the Mikvah used Is sufficient for complete submersion, covering the whole body at one time.

6. The methods mentioned in this section involve complicated technicalities of essential laws, and, therefore, should not be practiced except in case of extreme necessity, and only by persons above the average in knowledge of, and in the observance of, Jewish precepts.

IV. The quantity of water required for a Mikvah

The quantity of water required for Mikvah is not to be less than forty se'ahs or, in modern measurements,

24 cubic feet, U.S.A. standard measurement
179.53 gaUons, U.S.A. standard measurement
679,608 cubic centimeters
679.6 litres

However, the depth of the water must be so that a person may, with reasonable convenience, be completely immersed therein, all of the body being covered at one time.

(a) Whenever possible, It is best to have the depth of the water about three and one-half feet, that is, about six inches above the waistline of the person using it, thus affording the most convenient way of immersion.

(b) As a matter of convenience, there will be given herein a number of diagrams, figures and examples of receptacles of various dimensions (ninety-two in all), which will contain the required amount of water.

(c) It must be borne in mind, however, that the amount of water referred to is the net measurement, the volume of water that must be inside the space of the Mikvah.

(d) About twelve inches of space above the water line should always be allowed. There is about six Inches rise when an ordinary person is immersed in such a quantity of water, and there should be another six inches allowed to prevent splashing or spilling of the water. Therefore, it will be noticed that in each diagram twelve inches space in height is added to the actual height of the water.

(e) All these figures are good for a matter of accuracy, but practically it is best not to go into fine fractions. Therefore, a column has been added which gives the total dimensions in simple mechanical measurements avoiding decimals - that is, a fraction over in length. That column also includes twelve inches additional in depth, allowing for the rise of the water and splashing.

Note from the webmaster: here we have omitted several pages of figures and tables that lay out possible measurements for rectangular, cylindrical and triangular receptacles that contain the halachically required amount of water for immersion. We will assume that you can easily work it out yourself - keeping in mind that you need to enclose at least 24 cubic feet of water and leave a vertical foot of freeboard at the top of the enclosure.

Note for advanced readers and students

How We Arrive at the Accurate Modern Measurement from the Ancient) Traditional Method of Calculation.

Although the egg is the fundamental unit comprising the se'ah, the volume of forty se'ahs of water required for a Mikvah cannot be determined accurately from measurements of an average hen egg of the present day. This is seen from the following table of the Talmudic system of volumetric measurement:

6 eggs equal I lug
24 eggs equal 4 lug equal 1 cob
144 eggs equal 6 cobs equal 1 se'ah
5760 eggs equal 40 se'ahs make 1 Mikvah

Now the size of an average hen egg of the present day, illustrated below, measures about 3.21 cubic inches, which equals 1/18 quart (U. S. A. standard measurement).

It follows that forty se'ahs would be equivalent to 320 quarts or 80 gallons, which is an absurdly small volume of water for a Mikvah. This shows that the average hen egg of the present day is far too small to be used as the fundamental unit of the Talmudic era.

The size of the egg actually used as the fundamental unit of measurement of the lug, cob, se'ah and Mikvah, may, however, be arrived at by calculation from the known volume of the Mikvah (which is 24 cubic feet, 41472 cubic inches, or 179.53 gallons) and the dimension of the thumb.

The dimension of forty se'ahs for Mikvah is clearly defined in the Talmud, and adopted as the rule in Yorah Deah CCI.I: that is, "an ammah by an ammah and three ammahs high (1x1x3) equals 44118.5 cubic thumbs." The average measurement of a thumb Is within 2% of the U. S. A. standard inch; hence a cubic thumb is 6% less than a cubic inch. The number of 44118.5 cubic thumbs required for the measurement of a Mikvah would therefore be equal to 41472 cubic inches; equal to 24 cubic feet; equal to 2x2x6 feet; equal to an ammah (which is accordingly 2 feet) by an ammah by three ammahs; containing in liquid measurement 179.53 gallons, or 679.6 litres.

Now as the volume of water required for a Mikvah equals 41472 cubic inches, or 5760 eggs, therefore the volume of one egg, used as the basic unit in the Talmudic system of volumetric measurement, is 41472/5760 or 7.2 cubic inches. An egg of this size is herewith illustrated:

All of this establishes the fact mentioned in the Talmud that there were two sizes of eggs, and the basic unit of the Mikvah obviously refers to the larger egg.


The volume of water required for the Mikvah is forty se'a-hs, or, in modern measurements,

24 cubic feet, U.S.A. standard measurement
179.53 gallons, U.S.A.standard measurement
679,608 cubic centimeters
679.6 litres

(Rabbi Miller includes here a table that shows the weight of 24 cubic feet of water at various temperatures. At room temperature 24 cubic feet of water weighs about 1490 pounds.)

V. Requirements for the receptacle containing the water for Tvilah

1. The ritual-font, Mikvah, the receptacle which contains the water for Tvilah, must not be of a portable nature. It must by all means be built in, set, and permanently attached to the ground or to a building.

2. No ready-made, portable receptacle can be used as a Mikvah - even when it is attached to the ground or building - if it is In the nature of a "vessel" or "utensil" capable of holding water while in its movable, portable state.

3. A vessel may become qualified and be made a proper receptacle to be used as a Mikvah for Tvilah, if and after the following rules and conditions are complied with:

The receptacle (a) is to be rendered incapable of holding water by making a hole, equivalent to one and one-half inches in diameter, at the very bottom (in which event the receptacle is no longer considered a "vessel or "utensil"); (b) after this is done, the receptacle is to be set permanently on or in the ground, or attached to the building in a permanent manner; (c) and then (and then only) the hole is to be mended or repaired; (d) the repair or mending of the hole must be done in such a way that when the receptacle is lifted from the ground, the hole will reappear; that is, the repairing material shall not be fixed to or be a part of the receptacle alone, but must depend also upon the support of the ground or the building, to hold water.

4. When a hole of any size [see note below] is made in the very bottom of a receptacle at the time of its construction for the purpose of connection with the drain-pipes or sewers, such a receptacle, when connected to the drain-pipes or sewers which are laid in the ground or attached to the building, becomes a permanent attachment to the ground, or/and building; the usual rubber plug, or any mechanical contrivance fixed - constructed - in the drain for retaining the water, is also proper to retain the Mikvah water. The receptacle thus complies with all the requirements above enumerated, and, therefore, is proper to be used as a Mikvah for Tvilah.

NOTE: Such a hole does not need to be one and onehalf inches in diameter, since the receptacle never reached the state of a utensil.

VI. Public bathing places for Tvilah

1. Surf-bathing places, of such water mentioned in Paragraphs I and 2, Section II, this Chapter, which, as a rule, comply with the requirements of Mikvah water as to the quality and quantity, may be used as a Mikvah for the performance of Tvilah.

2. A floating bath-house, or stationary bathing houses built on the surf - where the bathing is in natural water which, as a rule, does not discontinue in the dry season - and where there are openings at the bottom of the bathing pool, the water in the pool being in contact with the main body of water, can be used as a Mikvah for Tvilah.

3. A public swimming pool or swimming tank, whether at a beach, or inland, or a public plunge, which as a rule is built permanently and attached to the ground, the water therein being conveyed not by hand, or by animal or man-power, and which, of course, contains the quantity oi water required for Mikvah, is proper to be used as a Mikvah for Tvilah.

NOTE: Although the public bathing places above cited are proper for woman's purification - Tvilah - according to the Jewish law, nevertheless, when there is in that vicinity a regular Mikvah, supervised by Jewish authorities, reasonably inviting and sanitary, it is best to patronize it, for many reasons (See Sec. IV, "Fundamental Rules of Nidah-Tvilah"). However, when it is inconvenient to reach a regular Mikvah, or if a woman hesitates to go there for reasons of her own, she is justified in making use of any natural Mikvah or public bathing waters, for Tvilah. (Consult "Fundamental Rules of Nidah-Tvilah," Section V.7 this work, for special rules when using a public place as a Mikvah.)

VII. A Bathtub is not a Mikvah

1. From this summary of the fundamental rules of Mikvah, It is clearly seen that an ordinary house bathtub is NOT a Mikvah. The bathtub has no qualification or possible claim to be considered as meeting the religious requirements of a Mikvah; and no Jew should entertain any idea or persuasion of that kind for one moment.

2. A woman who uses a bathtub as a means of purification is, according to Jewish law, not purified, and she remains a Nidah at all times, until she goes through the process of a formal and ordained Tvilah in a proper Mikvah, in such a manner as described in this chapter and in the one entitled, "Fundamental Rules of Nidah-Tvilah."

NOTE : All the rules involving Mikvah are too voluminous to be quoted in this work. We have cited only the fundamentals, the most prevalent and applicable ones. However, should a question arise, or a case develop, for which the ruling cannot be found directly in these chapters, then a proper, authoritative learned rabbi should be consulted.

From here you can move up one level or you can go on to read Chapter 19 of Secret of the Jew.