The Torah commands us to immerse metal  utensils that are purchased or otherwise acquired from a non-Jew in a mikva prior to their first use.  This mitzva is referred to as "tevilat keilim", the immersion of utensils. It is suggested that tevilat keilim, which appears in the Torah following the battle with the Midianites, was a mitzva intended to remove impurity from the utensils which had been in the presence of the dead. 
The mitzva of tevilat keilim is often compared to the conversion of a Gentile to Judaism - just as a conversion to Judaism requires immersion in a mikva, so too a utensil which "converts" from Gentile to Jewish ownership requires immersion, as well.  One is not required to immerse utensils which one borrows from a non-Jew. As we will see, the mitzva of tevilat keilim generally applies only to metal and glass utensils.
- 1 Basics
- 2 Procedure of Tevilah
- 3 Bracha
- 4 Which vessels require Tevilah?
- 5 Electric appliances
- 6 A Convert’s Obligation in Tevilat Kelim
- 7 If one didn't immerse a utensil
- 8 Links
- 9 Sources
- Utensils used for a meal that are bought from a non-Jew require Tevilah (immersion in a kosher mivkeh). 
- One who is unsure whether or not one's utensils were purchased from a Jewish owned company should immerse them without reciting the accompanying blessing. 
- It is actually a matter of dispute amongst the authorities whether the mitzva of tevilat keilim has the status of a Torah commandment or a rabbinical one. Nevertheless, most halachic authorities treat tevilat keilim as a Biblical mitzva for all intents and purposes. 
Procedure of Tevilah
- One should hold the vessel loosely. 
- One must immerse the entire vessel at one time and not half at a time. 
- One must make sure to remove all stickers, labels, and rust. 
- The utensil is immersed once, ensuring that it is completely covered by the water of the mikva. 
- One should remove a knife from the case before immersion. 
- A child under Bar Mitzvah can only do Tevilah in the presence of an adult and he can even make the Bracha.  It is best not to allow a minor to perform the immersion. 
- Tevilat keilim is not to be performed on Shabbat or Yom Tov. 
- A non-kosher utensil should first be kashered prior to immersing it. 
- It is unclear whether or not one who converts to Judaism is required to immerse the utensils he already owns. 
- For one vessel the Bracha is Al Tevilat Kli and for multiple vessels the Bracha is Al Tevilat Kelim. After the fact, if one switched Kli for Kelim or the opposite one has fulfilled one’s obligation. 
Which vessels require Tevilah?
- While the immersion of metal utensils is required by Torah law, glass utensils must be immersed only by rabbinic enactment. Glass was incorporated into the mitzva of tevilat keilim because glass and metal share a common characteristic - they are both materials which can be melted and reconstructed when needed. 
- Metal, glass, crystal, pyrex, and duralux require Tevilah. However, plastic, nylon, earthenware, and vessels covered in earthenware do not require Tevilah. 
- Some say that porcelain requires Tevilah, 
- Plastic or wood cutting boards do not need Tevilah, but those who are strict and do Tevilah for it will be blessed. 
- One need not immerse earthenware dishes, even if they contain some sort of glass coating or finish. Those who nevertheless choose to immerse glazed earthenware dishes or fine china must do so without reciting the blessing, as the immersion is not truly required.
- Similarly, jars, bottles, or metal containers which are used only to store food and not used for food preparation or consumption should be immersed without a blessing. Utensils which are only used indirectly with food, such as bottle openers, and the like, do not require immersion. 
- Common custom is not to require the immersion of plastic utensils even though some authorities argue that the similarities between glass and plastic would require it. 
- Utensils which one is certain that they contain no glass or metal components need not be immersed. 
- Due to the doubt whether or not Corelle dishes are halachically similar to glass dishes, they too should be immersed, though the accompanying blessing is not recited. 
- The mitzva of tevilat keilim only requires one to immerse those utensils which are intended to be used in food preparation or consumption. Although disposable utensils, such as aluminum pans, need not be immersed, one who intends to re-use them a number of times should do so. 
Tevilat Kelim on Snapple Bottles
- One of the most famous practical issues of tevilat kelim is glass bottles like Snapple. This seems to be a big issue as it is a vessel that we drink from (so it is klei Seudah), so it should require tevilah. Some think that one use would be allowed even without tevilah, but that seems to be made up. So just because we are richer than we used to be and throw out (or recycle of course) this perfectly good glass bottle, should that exempt us from tevilas keilim?
- Rav Hershel Schachter (Ten Minute Halacha - Practical Tevilas Keilim Issues by Rabbi Aryeh Lebowitz, min. 8) says that in fact it is forbidden to drink from these bottles. Rather, when you open the bottle, you must pour the contents into another vessel before drinking. On the other hand, Rav Moshe (Igrot Moshe YD 2:40) writes that it is not an issue to drink from the Snapple bottle since the Jew who opens it is considered the one who created the vessel and then it would not require tevilah. Chacham Ben-Zion Abba Shaul (Or Litzion OC 1:24) agrees. Alternatively, R' Yechiel Yaakov Weinberg (Sridei Esh YD 2:29) suggests a different solution. He says when you buy the Snapple, just have in mind not to acquire the bottle and then you have no issue as you do not own the vessel and you can drink from the bottle. Rav Menashe Klein (Mishne Halachot 4:107) writes that it is permissible since one doesn’t have in mind to acquire the bottle because nobody wants to buy something prohibited.
Tevilat Kelim on Aluminum
- The Gemara (Avoda Zara 75b) learns from the pesukim by the war with Midyan that when one buys utensils from a non-Jew one must immerse them in a mikveh before using them. Metal utensils are obligated in Tevilat Kelim. Though aluminum is scientifically a metal, there is a discussion in the poskim whether aluminum is considered a metal according to the Torah. In any event, our minhag is to be strict in this regard.
- Regarding aluminum tins, which are commonly only used once and then disposed of, there is a new point of discussion. Rav Moshe Feinstein (Igrot Moshe YD 3:23) proves from the rishonim that utensils which don’t last for an extended period of time, such as a vessel made from a pumpkin, don’t accept tumah. He assumes that since temporary vessels don’t qualify as a vessel for tumah, it must not also with regards to tevilat kelim. Seemingly, this applies to aluminum pans. Nonetheless, he adds, that vessels which could last a long time but are disposed of because they are cheap would certainly be obligated in tevilat kelim, even for a single use. Some, however, argue that even such vessels don’t qualify as a vessel.
- Modern-day electrical appliances present the mitzva of tevilat keilim with its biggest challenge. This is, of course, because water can damage electrical appliances or even cause harm to those who use the item following the immersion. There are differing approaches among the halachic authorities as to how one should to proceed with such items. Some authorities are of the opinion that anything which must be plugged into the wall in order to be used is halachically considered as if it were attached to the ground and anything which is attached to the ground is exempt from tevilat keilim.  Most authorities, however, reject this comparison and require even electrical items to be immersed just like all others. While some of these authorities require the entire item to be immersed along with all its electrical components, others say that only the actual components which come in direct contact with food need be immersed. 
Hot Water Urn
- A metal hot water urn does require tevilah with a Bracha. If its impossible to tovel it, one may give it to a non-Jew as a present on condition that he lend it back to you and it will not be obligated in Tevilat Kelim.
- According to many authorities a toaster requires Tevilah with a bracha. However, some argue that it doesn't require Tevilah.  Sephardim hold that that it requires but should be done without a bracha. 
- If the toaster will brake by being dipped in the mikvah one should either bring it to an Jewish expert mechanic who will take it apart (to the point that no everyone would know how to fix it) and put it back together or to give it to a non-Jew and then borrow it from him. 
- Some say that a microwave (glass) tray which does not touch food doesn't require Tevilah, and if it does touch food then it requires Tevilah. However, some say that one should dip it without a bracha in all cases. 
A Convert’s Obligation in Tevilat Kelim
- There is a mitzvah to dip in a mikveh food utensils that one buys from a non-Jew called Tevilat Kelim. An interesting case arises when a non-Jew converts to Judaism. Are his pots, pans, and silverware considered as though they were acquired from a non-Jew, requiring Tevilat Kelim? Or, perhaps the mitzvah only applies when buying utensils and not when the utensils remain in the same domain.
- Rav Ovadia Yosef (Yabia Omer YD 7:8) entertains the possibility of exempting a convert from Tevilat Kelim because this situation isn’t similar to the original story of Bnei Yisrael acquiring utensils from Midyan in which the utensils changed domains and not that the owners have undergone a transformation. Rav Wosner in Shevet HaLevi (4:92:2) disagrees and says that even though the form of acquisition isn’t identical to the original story, the fundamental transfer from a secular domain to one of kedusha is applicable to a convert. Interestingly, the Sochachover Rebbe (cited by Yabia Omer) argued that the convert’s undergoing of conversion is sufficient to also convert his utensils and exempt them from any obligation of Tevilat Kelim. Rabbi Aryeh Leib Grossnass (Lev Aryeh Siman 25) recommends doing tevilat kelim without a bracha because of the dispute.
If one didn't immerse a utensil
- A utensil may not be used, even once, before it is immersed in a mikva. 
- One, who for whatever reason, is unable to immerse a utensil which is urgently needed should give the item to a Gentile as a gift and then borrow it back from him. 
- If foods were placed upon or served with utensils which were not immersed in a mikva, it does not render the food non-kosher, though one should not eat off such utensils. 
- Kosher food which was cooked in utensils which were not immersed in a mikva but is then served on dishes that were (or disposable dishes) may be eaten without hesitation. 
- Gold, silver, copper, iron, tin, and lead are all types of metal.
- Bamidbar 31:23;Rashi, Avoda Zara 75b
- Rashi;Bamidbar 31:23
- Rashba;Yevamot 47b,Yerushalmi Avoda Zara 5:16
- S”A Y.D. 120:8, Kitzur Shulchan Aruch 37:5
- S”A YD 120
- Igrot Moshe Y.D. 3:21
- Yabia Omer Y.D. 2:9
- Aruch Hashulchan Y.D. 120:4, Sh”t Yechave Daat 4:64
- Halichot Olam (vol 7, pg 253), Yalkut Yosef (Kitzur S”A YD 120:5)
- Halichot Olam (vol 7, pg 253), Yalkut Yosef (Kitzur S”A YD 120:5)
- Yalkut Yosef YD 120:6, Kitzur Shulchan Aruch 37:10
- Kitzur Shulchan Aruch 37:10
- Yalkut Yosef YD 120:6
- Yalkut Yosef YD 120:25, Sh”t Yabia Omer 2:9(8)
- Y.D. 120:14, Kitzur Shulchan Aruch 37:12
- Kitzur Shulchan Aruch 37:13
- Y.D. 121:2, Kitzur Shulchan Aruch 37:4
- Sh"t Shevet HaLevi 4:92, 6:245(2) holds that a convert is required to immerse his vessels. Sh”t Yabia Omer YD 8:7 writes that seemingly the convert wouldn’t be obligated to immerse the utensils and quotes the Sefer Devarim Achadim (Rav Eliyahu Kalskin Siman 196), Shem MeShmuel (Parshat Matot), Sh”t Nezer HaKodesh 17 who agree. Yabia Omer concludes that one should immerse metal vessels without a Bracha and one wouldn’t need to immerse glass vessels. See Tzitz Eliezer 8:19-20, 22:49.
- Yalkut Yosef YD 120:7
- Aruch Hashulchan Y.D. 120:25
- Sh”t Yabia Omer 4:8, Hilchot Tevilat Kelim (Rabbi Moshe Fariz, 2:2-3)
- Hilchot Tevilat Kelim (Rabbi Moshe Fariz, 2:6) explains that even though some poskim held that it wasn’t obligated that was only because they were discussing porcelain which was ceramic not covered with glass, however, nowadays the common porcelain is covered with glass and must require Tevilah. Sh”t Yabia Omer 4:8 writes that porcelain doesn’t require tevilah.
- Hilchot Tevilat Kelim (Rabbi Moshe Fariz, 2:2-4)
- Igrot Moshe Y.D. 2:46
- Shach Y.D. 120:11, Kitzur Shulchan Aruch 37:8-9, Shevet Halevi 6:245:4
- Melamed Lehoil 2:48
- Tzitz Eliezer 7:37, 8:26, Chelkat Yaakov 2:163, Yabia Omer Y.D. 4:8
- Kitzur Shulchan Aruch 37:3
- Star K and OU write that corelle dishes require tevilah with a bracha. Rabbi Binyamin Forst and Rabbi Doniel Neustadt agree. Rabbi Tzvi Haber of Los Angeleswrites that the obligation to immerse corelle is questionable and so one should dip it without a bracha.
- Rambam Keilim 7:5, Igrot Moshe Y.D. 3:23
- Minchat Yitzchak 5:32
- S"A YD 120:1
- See Rav Yacov Kamenetsky in Emet LeYacov (YD 120:1). He concludes that you should dip without a beracha.
- Rav Hershel Schachter in a shiur on yutorah.org “Hilchos Tevilas Keilim”, Iggerot Moshe YD 3:22
- An article on ou.org writes that aluminum pans are exempt according to Rav Moshe. Mishneh Halachot 7:111 fundamentally agrees with Rav Moshe but writes that aluminum pans are obligated since it could be reused many times.
- Chelkat Yacov YD 46, OC 152:2, Minchat Yitzchak 5:32
- Chelkat Yaakov 1:126
- Igrot Moshe Y.D. 1:57-58, Chelkat Yaakov 3:43
- Star-K Tevilas Kelim Guidelines, Kof-K article, Rabbi Mordechai Eliyahu
- Rabbi Mordechai Eliyahu explains that if its impossible to do tevilat kelim on a hot water urn or the like one may give it to a non-Jew on condition that they lend it back to you and then it will not require Tevilat Kelim.
- Mishneh Halachot 9:162, Bear Moshe 4:100, Teshuvot VeHanhagot 1:450, Sefer Tevilat Kelim 11:52 quoting Rav Shlomo Zalman and Rav Wosner, Bayit HaYehudi 39:6, Kof-K quoting Rav Yacov Kamenetsky that such is the minhag
- Sh"t Igrot Moshe YD 3:24
- http://halachayomit.co.il/QuestionDetails.aspx?ID=160 which is based on the opinions of Rav Ovadyah Yosef
- http://halachayomit.co.il/QuestionDetails.aspx?ID=160, http://www.moreshet.co.il/web/shut/shut2.asp?id=118646
- Rabbi B. Forst http://www.kashrut.com/articles/tevilas_keilim/
- Bayit HaYehudi 39:6, Tevilat Kelim 11:14, Mishneh Halachot 2:32
- Rema Y.D. 120:8
- Y.D. 120:16;Rema
- Rema Y.D. 120:6, Beiur Halacha 323
- Igrot Moshe 3:22
- Rama Y.D. 120:16, Igrot Moshe Y.D. 2:41