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7. Going to Mikvah on Shabbos:
A person is allowed to purify himself of his impurities by immersing in a mikvah on Shabbos even if this immersing is Biblically required [to be done], such as a nidda and the like. [It is permitted to do so even if one was able to immerse before Shabbos.]
The reason that this is allowed is: being that doing so does not appear like one is rectifying [something on Shabbos which is forbidden] but rather like one who is going [in the water in order] to cool himself off.
Dipping in putrid water, and dipping in the winter: [Furthermore] even to immerse in putrid water which is not commonly used to cool off in, and even [to immerse] in the winter when it is not at all common to [immerse in water to] cool oneself off, nevertheless [it is allowed as] at times when a person is dirty from mud and feces he washes himself even in the winter and even in putrid water in order to remove the mud and feces that are on him.
The custom regarding a woman’s immersion: [However] in our provinces the custom is to forbid the immersing of a woman on Shabbos unless her husband is in the city as well as that it was not possible for her to immerse before Shabbos or [she was able to but] her husband was not in the city and only arrived on Erev Shabbos in which case she was not negligent in not having immersed prior to Shabbos. However in any case that her husband was in the city and she was able to immerse [before Shabbos] and did not immerse then she may not immerse on Shabbos.
The reason behind this custom: There are authorities which have given [the following] rational behind this custom [saying] that since the custom has spread to not bathe on Shabbos therefore when an impure person immerses to purify himself it appears as if he is rectifying [an item which is forbidden to do on Shabbos] and not like he is going in [the water] to cool off, being that it is not at all common to bath in order to cool off due to the reason explained [above in Halacha 2] even though that there is no prohibition in doing so.
The custom regarding immersing for purification of nocturnal emission: Nevertheless a man is allowed to immerse [to purify himself] from a seminal discharge. [See Q&A regarding immersing for prayer]
The immersion of a penitent: (As well an apostate that repented is allowed to immerse on Shabbos because this immersion is not Biblically required as opposed to the immersion of a convert (as well as that there is not even a complete Rabbinical obligation [for the penitent to do so])).
A woman who needs to re-immerse on Shabbos due to a stringency: As well any woman which needs to re-immerse due to a mere stringency is permitted to immerse on Shabbos as explained in Yorah Deah chapter 197 [Halacha 1 in Shach].
Summary-Going to Mikvah on Shabbos:
For penitence or for Keri: Is permitted to be done in cold water, even if the water is murky, and even in the winter.
A Nidah: Is from the letter of the law permitted to immerse, although the custom is to only allow her to immerse if her husband is in town and she did not have a chance to immerse prior to Shabbos, or had a chance but her husband only arrived on Erev Shabbos. A woman may always immerse if she is only required to do so as a mere stringency. [According to all, a woman may immerse on Shabbos if she was unable to do so due to a physical impalement, such as being after birth.]
Q&A on a women’s Immersion [Yoreh Deah 197]
If the wife knows that her husband is arriving on Erev Shabbos is she to immerse on Friday night or Thursday night?
She is to immerse on Thursday night. This applies even during other days of the week; that if her husband is arriving the next day, she should immerse the night before. She is to sleep that night with a knife under her pillow, or is to spread a clothing of her husband over her. [Nevertheless, if she did not immerse on Thursday night, she may nevertheless immerse on Friday night being her husband was not in the city.]
What is the definition of negligence that we prohibit her to immerse on the night of Shabbos?
Example: Wedding on Thursday night; Busy on Thursday; Purim on Thursday night etc
Some say so long as there is a valid reason for pushing it off, it is valid, and only when absolute negligence and carelessness are we Machmir.
If the couple had a fight and she did not immerse on Thursday night, may she immerse on Friday night?
If ones Mikveh night fell on the night of her Veses which is Thursday night, when is she to Tovel?
On Thursday night. They may not have Tashmish and she is to sleep with a knife and Beged. If, however, she did not do so, she may Tovel on Friday night.
What is the law if one transgressed and immersed in a case that she was not allowed to do so, is she considered pure?
If this was done advertently, despite knowledge of the prohibition, then she remains prohibited to her husband until after Shabbos. If, however, this was done inadvertently, without prior knowledge of the prohibition, then she is permitted to her husband.
Does the above prohibition apply also on Yom Tov?
Some opinions say that Yom Tov initially maintains the same laws as do Shabbos in this regard, however stating that Bedieved, after the fact, she is considered pure even if she immersed advertently despite knowing of the prohibition. Other Poskim however argue on this saying that there is no prohibition at all to immerse on Yom Tov in any circumstance and she may do so even initially.
If one was not required to wait 5 days in those cases in which it is explained that there is no need to do so, but did so anyways, may she immerse on Shabbos if that’s when her 7th clean day falls on?
Some Poskim rule this is forbidden to be done, and if one did so she may not immerse on Friday night. Others however rule it is permitted to be done and she may therefore immerse on Friday night.
If by mistake a woman did not do her Hefsek Taharah on time [before Sunset], and this thus caused her Mikvah night to be pushed off a day later which is Friday night, may she immerse?
May a woman after birth push off her Hefsek Taharah to Friday which may cause her to go to Mikveh on Shabbos?
She may do so according to all if she does not feel physically ready to go to Mikveh until that time. If she does feel ready beforehand and pushed it off for other reasons, then this matter is disputed as mentioned above.
Q&A on Men immersing in Mikveh on Shabbos
According to today’s custom to not bathe at all on Shabbos may one nevertheless immerse in a Mikveh on Shabbos?
Yes, not only is it allowed but it is even a Mitzvah to immerse for the sake of purification from nocturnal emission or even for additional purity as is customarily done on Shabbos morning prior to prayer. However, one must nevertheless take caution not to squeeze any of his hair.
How many times is one to immerse in the Mikveh on Shabbos day?
It suffices to immerse one time. [Although if one is a Baal Keri] he is to immerse twice.
May one do a Nine Kavim shower on Shabbos if a Mikveh is not available?
May one who desires to immerse in a Mikveh do so even in a river or sea?
Yes. One who needs to immerse due to nocturnal emission [or Tosefes Kedusha, and a regular Mikveh is not available] may do so even in a river or ocean, although taking care to avoid transgressing any of the matters mentioned in Halacha 2. However, there are Poskim which prohibit immersing in any water that is not within a private domain. From Admur, it is implied like the former opinion.
May one immerse in a hot Mikveh on Shabbos?
Warm: It is permitted to immerse in a warm Mikveh without question, just as is the law regarding a cold Mikveh. Regarding the definition of warm versus hot: The Poskim define warm as “no longer called hot” or below 98.6 Fahrenheit, and thus it must be below this temperature to be allowed without question, otherwise it has the status of hot water. See however Halacha 1D that according to Admur there is room to learn that so long as it is below Yad Soledes it is considered warm and not hot.
Hot: Some Poskim prohibit immersing in a hot water Mikveh on Shabbos, based on the prohibition against bathing the majority of one’s body in hot water on Shabbos. This applies even to women who have a Mitzvah to immerse, and certainly applies to men. Other Poskim, however, permit immersing in even hot water for the sake of a Mitzvah [such as women immersing for Nida, or even men who immerse for Taharah or Baal Keri purposes]. Practically, the widespread custom is like this approach. However, some are initially stringent like the former opinion and immerse in only warm or cold water. Nevertheless, one may not remain in the water for pure pleasure purposes and is rather to immerse and immediately leave. Those who stay in the water more than necessary transgress the bathing prohibition according to all, and must be protested and told to leave. However, one may immerse in the water as many times as he is used to doing during the week.
Custom of the Sephardim: The custom of Sephardi women is to immerse in hot water during Bein Hashmashos of Friday night. After Bein Hashmashos, they may only immerse in warm water. [Accordingly, Sephardi men are certainly to avoid immersing in hot water on Shabbos.]
If the water was heated on Shabbos through a timer or gentile? Some are accustomed to be lenient to allow immersing in such water however many have written against doing so. The Igros Moshe allows one to Bedieved use such a Mikveh even if it was heated by a Jew on Shabbos. [Opinion of Admur: Seemingly according to the ruling of Admur above in Halacha 1 that even water warmed on Shabbos in a permitted way may not be placed on one’s body, this would be forbidden.]
Does the water of a hot Mikveh need to be heated to its halfway point before Shabbos?
Night Mikveh: If the Mikveh is to be used at the night of Shabbos [such as a women’s Mikveh], then it is to be pre-heated before Shabbos to its halfway point. If this is not able to be done, one should lock the room that has the temperature settings, and this is considered as if he covered the fire [under a pot of food].
Day Mikveh: If the Mikveh is heated for the day [such as a men’s Mikveh] one is likewise to verify that the Mikveh reach its halfway point before Shabbos, or at the very least lock the thermostat area. However there are opinions which say that there is no need to verify that the water be preheated halfway before Shabbos.
May one swim in a Mikveh on Shabbos?
Depends on the Mikveh. See Halacha 8 Q&A there!
May one splash away the dirt that floats on the surface of a Mikvah?
Yes. See Halacha 9 Q&A there.
May one take a cold shower after the Mikveh to wash off the Mikveh water?
Seemingly yes, just as one may stay in the cold or warm Mikveh water for an extended period of time, if the water is cold.
May one remove the stopper which attaches the Mikveh to the pit of rainwater?
 Admur 326:7; See Shabbos Kehalacha p. 196-210
 Admur ibid; Michaber 326:8; Beitza 17b
 Admur ibid as implied from Gemara ibid; Rama 197:2 in name of Rishonim
 M”B 326:24; Gemara ibid
 Admur ibid; M”B 326:24; Rava Beitza 18a
 Admur ibid; M”B 326:24
 Admur ibid; M”A 326:8; Terumos Hadeshen 255; Maharil 139; Rama Yoreh Deah 197:2; Bach 197; Shach 197:3; M”B 326:25
Other opinions: The Beis Yosef [brought in Shach 197:3] rules that there is never a prohibition to immerse on Shabbos in any situation. [Vetzaruch Iyun if this is even if she could have immersed beforehand? Seemingly yes, as so is implied from the fact that the Michaber never rules anywhere regarding any restrictions in immersing on Shabbos, and rather wrote simply that one may immerse on Shabbos.] Others rule that it is forbidden to immerse on Shabbos even if [she had holy reasons to avoid doing so beforehand, such as that] her husband did not arrive until Erev Shabbos. [stringent opinion in Rama ibid; Taz 197:4 based on his understanding of the Terumas Hadeshen] However he too agrees that in a case that she could not immerse due to a physical impracticality [Oness], such as that she is after birth and did not have the strength to immerse beforehand, then it is allowed. Thus, the Taz argues on Rama which holds that it is dependent on the custom and rather rules that it is always forbidden unless it was physically impossible for her to do so. In the Nekudos Hakesef the Shach debates against the ruling of the Taz and supports the ruling of the Rama and Bach.
Custom of Sephardim: The Sefaradim are accustomed to be lenient in this matter and immerse on Friday nights. [Beis Yosef ibid; Rav Poalim O.C. 4:12; Mizbeiach Adam 199; Kneses Hagedola 197:5; Shulchan Gavoa 197:4; Taharas Habayis 2:454; However, see Darkei Taharah p. 170 that writes to be stringent in this matter as rule Admur here and Rama ibid.]
 See Rama Yoreh Deah 197:2 which implies that it is forbidden from the letter of the law. However, to note that in Orach Chayim 326:8 the Rama does not make any mention against bathing in a river or against immersing on Shabbos, of which the Michaber rules there that it is permitted. Vetzaruch Iyun as to why no gloss was written by the Rama being that he in truth holds that it is forbidden, as he writes in Yoreh Deah. Perhaps then one can say that the Rama too agrees that it is permitted from the letter of the law and that just due to the custom it is forbidden, as is the common explanation in other contradictory rulings. Vetzaruch Iyun.
 Admur ibid; 613:20; Rama 197:3 based on Terumos Hadesehn 195; This follows Michaber ibid and Rabbeinu Tam in Tosafus Niddah 36a and Yuma 8a that there is no Mitzvah unless the husband is in city.
Other rulings of Admur and other Poskim: However see Admur Y.D. 187:8 that it is forbidden for a woman to delay her Tuma even if her husband is not in the city, and so rules Shevet Hamussar 24; Darkei Teshuvah 184:64. [See Likkutei Sichos 14:27 footnote 58 that leaves this in Tzaruch Iyun; See Taharah Kehalacha 21:1; See there Biurim 1 for explanation of Admur ibid however practically, the custom is not to immerse when the husband is not in the city, even during the week. [See Piskeiy Teshuvos 240 footnote 45; Shiureiy Shevet Halevi 197:1; Taharah Kehalacha ibid]
 Admur ibid; Rama ibid in Yoreh Deah 197:2; M”A ibid; M”B ibid
 Admur ibid; lenient opinion in Rama Yoreh Deah 197:2; Bach and Shach 197:3, based on their understanding of the Terumas Hadeshen ibid; Mahrshag 2:55; Shevet Halevi 4:107; Piskeiy Teshuvos 326:9
Other opinions: Some Poskim rule it is forbidden to immerse on Shabbos if it is not the night after the seven clean days, even if the husband was not in town. [stringent opinion in Rama ibid; Taz 197:4 based on his understanding of Terumos Hadeshen ibid; Maryu 48] The Rama ibid concludes and rules that “so is the custom in certain places, however in a community where there is no custom then one is not to be stringent.” As rules Rama, so rules also the Bach and Shach [Shach 197:3, based on their understanding of the Terumas Hadeshen] that the main opinion is like the lenient opinion and thus in a place where there is no custom one may be lenient. However, Admur rules simply like the lenient opinion that she may immerse in such a case and does not make any mention of customs. However, the Taz [197:4] rules [based on his understanding of the Terumas Hadeshen] like the stringent opinion in Rama that it is forbidden to immerse on Shabbos even if [she had holy reasons to avoid doing so beforehand, such as that] her husband did not arrive until Erev Shabbos. However, he too agrees that in a case that she could not immerse due to a physical impracticality [Oness], such as that she is after birth and did not have the strength to immerse beforehand, then it is allowed. Thus, the Taz argues on Rama which holds that it is dependent on the custom and rather rules that it is always forbidden unless it was physically impossible for her to do so. In the Nekudos Hakesef the Shach debates against the ruling of the Taz and supports the ruling of the Rama and Bach.
 Admur ibid; Shach ibid; Piskeiy Teshuvos ibid
 Admur ibid; M”A ibid; Implication of Rama ibid; Shach ibid; Terumos Hadeshen ibid;
 Admur ibid
 Terumos Hadeshen 255; Maharil 139; M”A 326:8; Taz Yoreh Deah 197:4; M”B 326:24
 Admur ibid; M”A 326:8; Olas Shabbos; Elya Raba Tosefes Shabbos; Shulchan Atzei Shitim; Aruch Hashulchan 326:10; M”B 326:24; Poskim in Piskeiy Teshuvos 326:9 footnote 118
Other opinions: Some Poskim rule a Baal Keri may not immerse in a Mikveh on Shabbos as it appears like fixing [Biur Hagr”a 326:8, brought Biur Halacha 326:8 “Adam Mutar”; See M”A 128:70 and Admur 128:57] Even according to this opinion however one may immerse if he became a Baal Keri on Shabbos. [M”B ibid; Biur Halacha ibid] However some were accustomed to be stringent even in such a case. [M”A and Admur ibid] The Gr”a, brought in Biur Halacha ibid rules that since today we are accustomed not to bathe even in cold water it therefore appears like one is fixing and one may thus not immerse for nocturnal emission. The Ketzos Hashulchan 133 footnote 8 however adds that today since many are accustomed to immerse for the sake of additional purity [which does not involve a fixing prohibition according to all] it therefore once again is unnoticeable that one is immersing for nocturnal emission and thus even according to the GR”A it would be allowed. See also Poskim in Piskeiy Teshuvos ibid who bring this ruling.
Ruling of Admur and M”A regarding Kohanim: In 128 the M”A 128:70 and Admur 128:57 explain that the Kohanim were accustomed not to do Nesias Kapayim on Shabbos due to the prohibition against immersing on Shabbos. See Nimukei Orach Chaim 326:1
 Admur ibid; M”A ibid
 Admur ibid; Machatzis Hashekel ibid; M”B ibid; Seemingly Admur here is coming to answer why be a Baal Keri we permit the immersion even though by Keilim we are stringent even though some rule that Tevilas Keilim is only Rabbinical.
 Admur ibid; M”A 326:8; Pischeiy Teshuvah Y.D. 268:10
 See Rama Y.D. 268:12
 Admur ibid
 Admur 326:7
 Taz 197:4
 Shiureiy Sheivet Halevi 107:2-1; Taharah Kehalach 21:5Nitei Gavriel 30:3 in name of Kinaas Sofrim 64; Taharas Yisrael 198:48; Implication of Darkei Taharah ibid; and so I heard from Rav Asher Lemel Hakohen
 Shvus Yaakov 3:77
 Kaf Hachaim 240:14-15
 See Shiureiy Sheivet Halevi p. 304; Taharah Kehalacha 21:11; Piskeiy Teshuvos 326:9; Nitei Gavriel vol. 3 31:8-11
 Piskeiy Teshuvos 326:9; Nitei Gavriel vol. 3 31:8-11
 Nitei Gavriel 31:6 in name of Daas Torah
 Taharah Kehalacha 21:10 in name of Vayan Yosef 29
 Toras Hashelamim 197:3; Pischeiy Teshuvah 5 in name of Shut Chut Hashani
 Toras Hashelamim 197:3
 Shut Chut Hashani
 Toras Hashelamim 197:3; Sidrei Taharah 197:2; Chochmas Adam 118:8; Lechem Vesimla 197:10; Levushei Mordechai 93; Shaareiy Tohar 17:4; Divrei Yatziv 104; Nitei Gavriel 31:13
 Shiureiy Sheivet Halevi p. 305; Taharah Kehalacha 21:10
 Nodeh Beyehuda 131; Pischeiy Teshuvah 197:4
 Daas Kedoshim in Daas Torah Mahrsham; Avnei Nezer Yoreh Deah 246
 Nodeh Beyehudah, brought in Pischeiy Teshuvah 197:2
 Ketzos Hashulchan 133:4 footnote 8; Aruch Hashulchan 326:10; All Poskim in Piskeiy Teshuvos 326:9 footnote 118
Opinion of Mishneh Berurah: The Biur Halacha 326:8 “Adam Mutar” rules that one is to avoid immersing for purposes of additional purity being that one may come to squeeze his hair, and it suffices that we already allow to be lenient to immerse for nocturnal emission. [Biur Halacha 326:8 “Adam Mutar”] The Ketzos Hashulchan 133 footnote 8 however takes to par this ruling of the M”B being that a) The source of the M”B is in the Mahril which sates with regards to women that would avoid immersing on Shabbos if that is not their Halachic date of immersing. Now the Mahril states that the reason for this stringency is to avoid any carrying of the water, swimming, squeezing hair. Now, regarding men immersing in an indoor Mikveh only the squeezing of hair is relevant and thus there is no source from the Mahril to be stringent when only one suspicion is relevant. Furthermore, the suspicion of squeezing hair is a lot more relevant by women than men, and thus there is no support from the ruling regarding women at all. b) The Arizal writes that it is a Mitzvah to immerse on Shabbos morning and it is thus considered its right time, as opposed to the ruling by women which involves a date which is not their correct time. c) The custom of not bathing in cold waters is itself a stringency and it thus suffices to be stringent to not bathe for pleasure, and not to extend this to even Mitzvah purposes. [ibid]
 The reason: The reason for this is a) As the Mahril states that the reason for the stringency against immersing is to avoid any carrying of the water, swimming, squeezing hair. Now, regarding men immersing in an indoor Mikveh only the squeezing of hair is relevant, which is easily avoidable, while the carrying and swimming issues are not relevant. Thus, one may be more lenient. Now although Admur wrote that “the custom is to not bathe at all on Shabbos “, nevertheless it is evident from the fact that later on Admur states the permission to immerse that this custom only applies to pleasure baths and not to baths motivated for other purposes. b) The Arizal writes that it is a Mitzvah to immerse on Shabbos morning and it is thus considered its right time, as opposed to the ruling by women which involves a date which is not their correct time. c) The custom of not bathing in cold waters is itself a stringency and it thus suffices to be stringent to not bathe for pleasure, and not to extend this to even Mitzvah purposes. [ibid]
[Ketzos Hashulchan 133 footnote 8]
 As writes the Arizal and other Mekubalim that one is to immerse on Shabbos. [ibid] The Arizal writes that if one is a Baal Keri or had Tashmish on Friday night then he is obligated to immerse on Shabbos day. Furthermore, he writes, even if the above did not occur one must still immerse on Shabbos day in order to garb his soul with the new revelations of Shabbos day, which one did not yet receive with his immersion done on Erev Shabbos. [Kaf Hachaim 260:6]
 So is the custom of majority of the Torah sages in Jerusalem of all sects, including the Sephardim and Perushim. [ibid]
 Kaf Hachayim 260:6
 So writes Arizal, in order to garb his soul with the holiness of Shabbos day. [ibid]
 Tosefes Shabbos; Ketzos Hashulchan 133 footnote 8; Piskeiy Teshuvos 326:7
 Pashut, as otherwise one enters himself into many worries of Shabbos transgressions, as explained above.
 The reason: As we did not accept this custom in the place of a Mitzvah such as Tevila. This is seemingly no different than women immersing on the night of their Mikveh.
 Minchas Yitzchak 6:32, Piskeiy Teshuvos 339:1
 So is implied from Admur 326:7 which does not differentiate between bodies of water, despite having brought the custom in 326:6.
 Regarding the Kashrus of a Hot Mikveh from the aspect of the laws of Mikvaos see Yoreh Deah 201:75 that Michaber forbids this even during the week [due to people coming to think that a bathhouse is also a Kosher Mikveh-Taz] while the Rama rules that in those places that are lenient may do so, although one is to be stringent. See as well Tikunei Mikvaos where Admur writes that hot water is placed into the Mikveh.
 See Pischeiy Teshuvah Yorah Deah 197:1 for a compilation of different opinions.; Shabbos Kehalacha 18:47; Piskeiy Teshuvos 326:5
 Chacham Tzevi 11; Nodah Beyehudah Tinyana Orach Chayim 24 [so writes Pischeiy Teshuvah as well as Divrei Chayim, however Tzitz Eliezer argues on their opinion in Nodah Beyehudah.]; Chayeh Adam 70:1; Chochmas Adam 122:22; Aruch Hashulchan 326:10; Rav Poalim O.C. 4:15; M”B 326:7 in name of Chayeh Adam; Igros Moshe 4:74; Or Letziyon 2:35-3; The Sheivet Halevy [5:44] rules that it is best to immerse in a warm Mikveh if he is able to, despite the fact that the custom is to be lenient.; See Poskim in Piskeiy Teshuvos 326:5 footnote 58
 Karban Nesanel [Perek Bameh Madlikin 22:11] says that this is not included in the decree against bathing; Bircheiy Yosef Yoreh Deah 197:2; Divrei Yosef 64, although he concludes with a Tzaruch Iyun [so says Pischeiy Teshuvah, however Tzitz Eliezer differs that he does allow it and so learns others as well]; Sidrei Taharah Y.D. 197:16; Chesed Lealafim 326:7; Divrei Chayim 2:26, Avnei Nezer 1:526; Darkei Teshuvah 197:7; Levushei Mordechai 1:1; Maharshag 2:127; M”B 326:7 brings the Karban Nesanel and in Shaar Hatziyon 326:5 writes one may be lenient in a time of need; Kaf Hachaim 326:33; Minchas Yitzchak 5:32; Tzitz Eliezer 6:22 brings many opinions which permit it; Divrei Yatziv 160-161; Orchos Rabbeinu 1:152 writes that Steipler would immerse in hot Mikveh if nothing else available; Sheivet Halevy 5:44 rules that it is best to immerse in a warm Mikveh if he is able to, despite the fact that the custom is to be lenient; See many Poskim in Piskeiy Teshuvos 326:5 footnote 54
 The Karban Nisanel ibid does not explicitly state why a Mikveh is not included in the decree of bathing, however the other Poskim who discuss his ruling record several reasons: 1) As many people are there and one will not come to transgress; 2) As it is done for the sake of a Mitzvah. 3) A mere dip is not considered bathing. Practically, the second reason is the main reason recorded behind the basis of this custom. [See Noda Beyehuda ibid; Avnei Nezer ibid; Divrei Yatziv ibid; Igros Moshe 1:126; Piskeiy Teshuvos 326 footnote 51]
 While many of the above Poskim discuss specifically a woman’s immersion it is evident that this would apply likewise to a man. Furthermore, some of the above Poskim explicitly write that this extends also to the immersion of a man. [See Chesed Lealafim ibid; Aveni Nezer ibid who permits but says Lechatchila is best for man to avoid if just for Tosefes Taharah; Divrei Yatziv ibid; Piskeiy Teshuvos 326 footnote 54 and 58]
 Divrei Chaim ibid
 See Piskeiy Teshuvos 326:5
 Avnei Nezer 1:526 “To sit in the hot Mikveh after immersing is certainly forbidden, however to enter, immerse and immediately leave has room for Halachic leniency” [However, based on reason 1 and 3 recorded above, even this would be allowed. However, practically the main reason is reason 2, and it is hence only permitted for the sake of a Mitzvah.]
Does this apply even if the Mikveh is warm? Seemingly, even if the Mikveh is not hot, but warm or cold, one is to leave right away, as it is nevertheless forbidden to bathe in even cold water due to custom. [See Lehoros Nasan 4:30; Piskeiy Teshuvos 326:5] However, perhaps we say that once one has entered with permission, there is no longer a custom to prohibit remaining a little longer. Vetzaruch Iyun
 See Piskeiy Teshuvos 326 footnote 56
 See Zera Emes 1:71; Rav Poalim 4:21; Or Letziyon 2:35-3; Yabia Omer 10:55; Darkei Halacha p. 169; Piskeiy Teshuvos 326 footnote 54
 Piskeiy Teshuvos 326:2
 Vetzaruch Iyun as perhaps since it’s not being done for purposes of bathing it is permitted even if the water is heated on Shabbos, as from the aspect of bathing the entire body it is equally forbidden to be done whether with water heated before or on Shabbos.
 Shabbos Kehalacha Vol. 1 page 332-333
 Admur 326:1 [There Admur explains like the Ran that it was due to this reason that the Sages forbade bathing on Shabbos in hot water as the Balanim were not careful to heat the water to the halfway point before Shabbos.]
 Rav Shlomo Zalman Aurbach brought in Shabbos Kehalacha ibid
 As is the simple understanding of the Admur 253:29; 254:14-15, and as is clearly ruled in 326:1 as rules the Ran [regarding the reason for the Issur of bathing on Shabbos] and 326:11 [regarding the Issur of bathing in hot water heated in a way that transgressed the Shehiyah restrictions]. So is also the custom of Rav Wosner to be stringent in the Mikveh under his ruling.
 Mahrsham 229; Sheivet Haleivi 7:32
 Mahrsham rules it is allowed being that one does not plan to use the water until the next morning and is thus similar to raw meat, and because in any event it is forbidden to heat the Mikveh too much due to the prohibition of bathing in hot water. These arguments however are not relevant today being that we are accustomed to immersing in hot water. Furthermore, Admur clearly rules that we suspect for stoking the coals even one leaves the food for the next day, and why should we differentiate between food and water of the Mikveh. Just like one may come to change his mind and decide to eat the food at night, perhaps one will desire to immerse in the Mikveh at night, past sunset on Shabbos. In any event the Mahrsham concludes that the fire [or area of raising the temperature] is to be covered.
 Ketzos Hashulchan 146 footnote 34:17 and 35; Shabbos Kihalacha Vol. 2 p. 242.
Splashing away dirt may involve the “Swimming” prohibition as well as the Borer prohibition .
 Piskeiy Teshuvos 226:5 [24 in new]
 So rules Darkeiy Teshuvah Yoreh Deah 201:27 which brings many opinions which allow this as to opposed to the Mahrshik which writes that its forbidden; So rules also that it is allowed: Igros Moshe [did not find source], Dvar Moshe, Mishneh Halachos.
 As purifying impure waters is allowed to be done on Shabbos through pouring them into a Mikveh. [Rambam Shabbos 23:8]
 Removing a pit cover may contain two prohibitions: Muktzah if it does not have a handle [308:37] and Setirah [if it is not made to constantly remove]. In this case neither prohibition applies as it is made to constantly open and close, as well as that it appears that it is made for doing so despite the fact that it does not contain a handle. [Sheivet Hakehasi 3:132]