Immersing vessels in a Mikveh:
It is forbidden to immerse a vessel in a Mikveh on Shabbos if the vessel requires immersion in order to be used. Thus any vessel bought from a gentile and has not yet been immersed may not be immersed on Shabbos. This applies even if one did not have the ability to immerse the vessels before Shabbos.
Giving the vessel to a gentile: Being that one may not immerse the vessel on Shabbos, and it is forbidden to use a vessel without immersion, one’s only option is to give the vessel to a gentile as a present and then borrow it back from the gentile. This however may only be done if one needs to use the vessel on Shabbos. In such a case, after borrowing the vessel back from the gentile one may use the vessel without immersion, as it now legally belongs to the gentile. Nevertheless after Shabbos one must immerse the vessel without a blessing [or immerse together with a vessel that requires a blessing]. [Alternatively one should ask the gentile after Shabbos to acquire the vessel back to him as a complete present, or the Jew should buy it back with a few coins, in which case one can make a blessing on the immersion of that vessel according to all.]
Immersing the vessel in an inconspicuous manner: It is permitted to immerse the vessel in waters that are Kosher for a Mikveh if it is unnoticeable to the onlooker that he is doing so to purify the vessel. Hence a pitcher and other vessel meant to draw water may be entered into the Mikveh waters to draw out water, hence purifying the vessel in the process. In such a case one may not say a blessing on the immersion, as if he were to do so it would be evident that his intents are in truth to purify the vessel. [Thus one who has other vessels available may not immerse the vessel in this method, as by doing so one is causing it to lose its blessing. Likewise only pitchers and cups may be immersed, as only they are capable of drawing water and hence fooling the onlooker. One however may not immerse cutlery and china in a Mikveh under the disguise that he is simply washing off the dirt from the vessels, as it is not common at all to do so in a Mikveh, and one’s true intent is hence evident to all. Based on this today that it is no longer common to draw water at all from a Mikveh or any body of water other than one’s sink, it would hence be forbidden to immerse vessels in a Mikveh under all circumstances, as doing so is always apparent of one’s true intention.]
The law on Yom Tov: It is forbidden to immerse vessels on Yom Tov just as is forbidden to be done on Shabbos. If however one did not have the ability to immerse the vessel at any time prior to Yom Tov and on Yom Tov his first opportunity to immerse them arrived, then he may immerse the vessel. Nevertheless one may not rule this way when asked this question, [and is rather to tell the asker that immersing vessels is forbidden in all
Washing off non-Kosher food from a utensil: It is permitted to rinse off a vessel that was used to eat non-Kosher food if one plans to use the vessel that day. This applies even if there is remnant of the non-kosher food on the vessel.
It is forbidden on Shabbos to immerse vessels in a Mikveh in all cases. If one needs this vessel for Shabbos and cannot do without it, then he may give the vessel to a gentile as a present and then borrow it back from him and use it without immersion.
After Shabbos he is to immerse it without a blessing.
May one immerse a vessel on Shabbos if there is a doubt as to whether it requires immersion?
Some Poskim rule that if there are no other vessels available, and one is unable to give it to a gentile, as explained above, then one may be lenient to immerse the questionable vessel whether it is made of glass or metal.
Others rule that if the vessel in question is made of glass then it may be used on Shabbos without being immersed and if made of metal it may be immersed.
 Whether made of glass, metal or any other materials which requires immersion. [See M”B 323/32 and so is implied from Admur which does not differentiate between the two]
 So concludes Admur in 323/5 [“and if one is unable to do the above, don’t immerse the vessels” and “if one transgressed and immersed the vessels”. So also summarizes the Ketzos Hashulchan 146/3 that doing so is forbidden.]
Background: Admur brings a dispute regarding this matter:
- The first [stam] opinion rules that new vessels may be immersed on Shabbos even if one was able to immerse them before Shabbos. Their reasoning is because according to them immersion is only Rabinically required for new vessels, while Biblically the vessels may be used without immersion. Hence immersing the vessel is not considered like one is fixing the vessel, as Biblically the vessel is already useable.
- Others however rule that immersing new vessels is forbidden due to it being considered like one is fixing the vessel. According to them this applies even if one did not have the ability to immerse the vessels before Shabbos.
- It goes without saying that immersing vessels is forbidden according to the opinion which rules that immersing new vessels is Biblically required. As on this premises by immersing the vessel one is doing it a significant fixture according to all, of which the Sages forbade being that it is exactly similar to fixing a vessel which is a Biblical prohibition.
- The practical ramification between the 2nd and 3rd opinion is regarding glass vessels, which according to all is only Rabbinically required to be immersed.
- Practically: One may not immerse vessels in a Mikveh on Shabbos as the main opinion follows the opinion which rules that immersing new vessels is Biblically required. [So concludes Admur in 323/5 and so summarizes the Ketzos Hashulchan 146/3. Vetzaruch Iyun from the wording of Admur prior to this ruling that “A G-d fearing Jew will fulfill his obligation according to all and give the vessel to a gentile…” Hence implying that from the letter of the law one may be lenient like the first opinion and immerse the vessel. So also implies the M”B [323/33] from this similar wording of Michaber, that the Michaber rules mainly like the first opinion that it is permitted. Thus how can Admur say that one who immersed the vessel has transgressed? Vetzaruch Iyun Gadol!!]
 As it is only permitted to give a present to a gentile on Shabbos if it is being done for the sake of Shabbos. [ibid]
 Being that this vessel will now remain in the hands of the Jew forever, and is thus similar to him having bought it. Alternatively it is similar to a borrowed Tallis which required Tzitzis after 30 days even though it is not his. Based on this it should be immersed even with a blessing. Nevertheless since I have not found the matter explicitly ruled in Poskim I am hesitant to rule this way, and rather one should immerse another vessel that requires a blessing together with it. [Yoreh Deah Taz 120/18]
 Taz in previous footnote. This applies even according to Admur, and the reason Admur did not state this explicitly is because he is dealing with a case that one only has this vessel to immerse. [Ketzos Hashulchan 146 footnote 6]
 Ketzos Hashulchan 146 footnote 6
 This does not appear like one is fixing the vessel, as it is not evident at all that one is intending to purify the vessel. This is because not everyone knows that this vessel has not yet been immersed hence causing the onlooker to say he is doing so in order to use the drawn water. [ibid]
 As for why a woman who immerses on Shabbos may say a blessing, this is because the Sages never originally decreed against women immersing on Shabbos. The reason for this is because at the times of the Sages it was not recognizable as to for what purpose the woman is immersing, and hence the Tikkun was never recognizable. Alternatively this is because the decree against immersing vessels is because one may come to actually fix a vessel which is Biblically forbidden. The Sages however were not this suspicious regarding a person immersing. [Ketzos Hashulchan 146 footnote 8]
 M”B 323/36
 Ketzos Hashulchan 146 footnote 7
Other opinions: However the Kaf Hachayim rules one may immerse all vessels in the Mikveh under the disguise that one is doing so to clean the vessel. The Ketzos Hashulchan argues on this saying that it is never common to wash dirt off vessels in a Mikveh, and hence all will know one’s true intents.
 So is clearly implied from Ketzos Hashulchan ibid regarding his argument against the Kaf Hachayim, and so is evident from the fact he writes that drawing water with the vessel is allowed because “at times today people do draw water from the Mikveh”. Now, although this may have been true in the 1950’s, the time of the publishing of this Sefer, today this is certainly not the case, and hence the Halacha likewise changes.
 As if Admur is referring to one who did so by mistake, then his ruling carries no novelty, as it is already ruled in 339/7 that no fine was enacted against Rabbinical decrees done inadvertently. Hence one must conclude that Admur includes even the advertent sinner in this ruling, that no fine was applied even to him.
 Although in general the Sages fined all transgressors against benefiting from their forbidden actions until after Shabbos, even by a Rabbinical transgression, nevertheless in this case no fine was given being that there are opinions which allow doing so even initially. [ibid]
 323/8; 509/15
Thus for oneself to do so is allowed, if he knows this Halacha, while for another, it is not allowed if he does not know this Halacha, and hence one may not tell him that it is allowed. The reason for this is because if they are told it is allowed they may come to also immerse vessels that could have been immersed before Yom Tov. [ibid]
 As this itself is considered as if one is ruling to them that immersing vessels is allowed, and they may come to immerse vessels even in cases that it is not allowed. [ibid]
 According to all this is not considered as if one is fixing the vessel as the actual vessel is permitted to be used and it is just that the non-Kosher food prohibits its use. Hence rinsing it off is similar to rinsing off feces from it. [ibid]
 Although non-Kosher food is Muktzah, nevertheless its remains are nullified completely to the vessel and do not have the ability to prohibit moving it at all. [ibid]
 M”B 323/33
 Kaf Hachayim 323
 As this is a doubt in a Rabbinical case in which the rule allows one to be lenient.
 Ketzos Hashulchan 146 footnote 5
 As even in a case of doubt we rule all vessels need to be immersed, even if made of glass, as one may not actively enter himself into a Rabbinical doubt by avoiding the immersion. Thus once again since the vessel is forbidden to be used until immersed even in a case of doubt we once again return to the same debate in whether this is allowed due to it appearing as if one is fixing the vessel. [ibid]