Question: May a mikvah contain warm water?

Short Answer: Yes, one may add warm tap water to our mikvaos, which are built by halachic mechanisms that permit tap water.


I. Background to Modern Mikvaos

The halachos and architecture of building modern-day mikvaos are understandably very complex. The following is a short synopsis summarizing the relevant background facts and issues for this article, taken primarily from the excellent work, Gray Matter II, by Rabbi Chaim Jachter shlita, and based on the sefer Mikve Mayim by Rabbi Yirmiyahu Katz.

While a spring (“maayan”) may serve as a kosher place to tovel, our mikvaos operate as a “mikvei mayim” and thus must consist only of “ashborin,” i.e., stationary water, such as rainwater. The exact amount of “zochalin” (flowing water) that renders a mikvah to be pasul, and whether this flowing water must be “recognizable” to make pasul the mikvah, is subject to halachic debate (See T’shuvos V’Hanhagos (1:513).

Even rainwater, however, is pasul for use as a mikvah if it is “mayim sh’uvin,” i.e., drawn water. Thus, tap water, which is from a reservoir but passed through “receptacles” in purification plants and through other devices (i.e., that are keilim) is pasul for use as a mikvah, as it is considered “mayim sh’uvin.” Even three lugim (less than one quart) of tap water “pasels” a mikvah.

Thus, the obvious question is: How may a modern, sanitary mikvah use tap water in a halachically permitted manner?

On a very basic level, there are essentially three practical ways to use tap water. First, through the halachic concept of “hamshachah,” which requires pouring the tap water on the floor outside of the mikvah, allowing them to flow naturally into the mikvah. Second, through the halachic concept of “hashakah,” which requires attaching a kosher mikvah with the requisite amount of rainwater to a “mikvah” filled with tap water (where the person immerses) via a pipe. Third, through the halachic concept of “z’riah,” which requires pouring tap water on top of a mikvah full of rainwater so that the tap water overflows off the kosher mikvah into an adjoining mikvah (where the person immerses).

There are many halachos surrounding the application of these concepts, but many modern mikvaos implement all three of these halachic concepts to create the mikvah.


II. Warm Tap Water

Based on the above, a significant amount of our mikvah water is tap water. May this tap water be heated, which certainly would aid in the comfort of immersing in such a mikvah?

The Gemara in Nidah (66b) cites Rava, who rules that a woman may not be tovel while standing on a utensil (i.e., in the mikvah). Rav Kahana suggested that the reason why it is forbidden is lest she come to be tovel in a “bathhouse” (Rashi: which typically had such utensils in the bath). However, Rav Kahana rules that standing on a log (in the mikvah) is permitted. On the other hand, Rav Chanan explains that toveling while standing on either a utensil or a log is forbidden, as we are afraid that the woman will not properly immerse because she is afraid of falling.

The Mordechai (cited in the Beis Yosef, Yoreh Dei’ah 201:75) cites this Gemara as a proof to his ruling prohibiting the adding of hot water to a mikvah (i.e., built based on hashakah), as we are afraid that the woman will come to be tovel in a bathhouse. The Mordechai likewise cites a Gemara in Taanis (13a) that states that immersing in warm water does not qualify as a kosher t’vilah.

The Shulchan Aruch (Yoreh Dei’ah 201:75) cites this opinion as a “yeish mi she’omeir” but does not cite any lenient opinion.


III. The Lenient View

The Darchei Moshe (ibid) cites the Hagahos Mordechai, who disagrees and allows the addition of hot water into the mikvah (which employs hashakah or the like). Additionally, he cites T’shuvas Binyamin Z’ev, which ideally is stringent, but notes that one may rely on the lenient opinions.

Thus, the Rama (ibid) rules that while some are lenient, ideally one should be stringent and not add hot water. However, one should not chastise those who have the minhag to be lenient and add hot water.


IV. The Aruch HaShulchan’s Explanation

The Aruch HaShulchan (201:215) explains why the Shulchan Aruch rules strictly and why the Rama, at the very least, notes the lenient opinion. The Shulchan Aruch (who lived in Spain, and later in Tz’fas) dwelled in warm areas and thus was able to rule stringently, that no additional hot water may be added. The Rama, on the other hand, was a rav in Krakow, Poland, which had bitterly cold winters, and thus needed to cite the lenient opinions.

The Aruch HaShulchan notes though that even the Rama rules that ideally one should be strict and not add warm water to the mikvah. However, the Aruch HaShulchan is emphatic that nowadays warm water must be added to the mikvah, as otherwise women would not immerse, and if they did, they would get sick. Thus, he rules leniently and concludes that he has not heard of anyone who is strict in this regard nowadays.

The Aruch HaShulchan also explains the Gemara in Nidah (cited above) as simply ruling that one may not be tovel in a utensil lest one immerse in a bathhouse. But adding water to our mikvaos, which are not utensils, is permitted.


V. The Igros Moshe’s Extrapolation

The Igros Moshe (Yoreh Dei’ah 1:111) interestingly extrapolates from this halachah that we do not always build mikvaos by incorporating all of the strict opinions. While it is certainly noble to build a mikvah incorporating a lot of different opinions, the fact that we add hot water shows that we do not always follow this rule.

In conclusion, the Mikve Mayim (Vol. 3, p. 13-17) does list many Acharonim who write how important it is to build mikvaos by incorporating as many opinions as possible. However, Rav Moshe clearly understands that this is only to a certain extent. Warm water may be added.

Next Week’s Topic: May one immerse in a private mikvah that was built or is maintained without rabbinic oversight?

Rabbi Ephraim Glatt, Esq. is Assistant to the Rabbi at the Young Israel of Kew Gardens Hills and a practicing litigation attorney. Questions? Comments? Email: This email address is being protected from spambots. You need JavaScript enabled to view it..