I've heard that there is a dispute among halachic decisors if one is allowed to use an urn like the one shown below on Shabbos

hot water urn with external tube to show the amount of water left

because the outside water tube gets cold over Shabbos but then gets reheated in the cup. Both sides agree that "Yesh bishul achar bishul" (there is cooking after cooking).

What is the argument? It seems to be a machlokes b'mtzius (an argument over a fact).

  • Are you talking about the particular urn, because there is a tube containing water that shows the fill level, or are you talking about any urn, because of concern that some water might be left in the spout?
    – Seth J
    Commented Jan 10, 2012 at 3:44
  • Nothing at all firm (which is why I'm not posting this as an answer), but an idea: There are, I believe, some who hold that if a few drops are left in the bottom of a cup then it can nonetheless be refilled with hot water. Perhaps whatever argument applies there applies here, too?
    – msh210
    Commented Jan 10, 2012 at 5:13
  • I imagine this is an argument about weather or not the water in the level guage actually gets replaced after a cup is filled or not and if it's replaced, if it's "completely" replaced. I think this is an argument about halacha not fact, because of what msh210 mentioned. But I'm not confident enough to post this as an answer.
    – avi
    Commented Jan 10, 2012 at 9:05
  • @ShmuelBrin could you name one or two halachic decisors from each side? Commented Jun 15, 2015 at 18:35

3 Answers 3


Rav Yechiel Perr told me that that after speaking to scientists he concluded that to use such an urn is not a problem as the water in the tube has already exchanged from the water inside.

The sefer Orchos Shabbos (Chelek 1: Perek 2: Seif 30) rules this as well. See note 47.

Rav Ben Zion Abba Shaul in Shu"t Ohr Letzion (Chelek 2 Perek 30 note 10) rules that even according to those that hold yesh bishul achar bishul this urn us not problematic.

This is not to be relied upon for practical halacha CYLOR


As Rabbi Willig explained it, one factor would be whether or not we are concerned with heating more water already above yad soledet bo. Another is if this water's temperature is in fact below that (say this water is at 140 F...is that above or below). There may well be other factors. Tipping the urn backwards before Shabbat to ensure all water is pre-boiled seemingly does help, and was in fact his advice in this case.


R. Ovadiah Yosef (Hazon Ovadiah Shabbat vol. 4, 414ff.) rules on this exact type of urn that it is permissible to use.

In presenting the question, he discusses various issues at play that are debatable:

  1. The water in the tube isn't boiling and therefore when water is released into the main vessel it will be cooked. However ROY dismisses this issue since it is unintentional and unnecessary for the user's purpose (דבר שאינו מתכוין, פסיק רישיה דלא ניחא ליה). Furthermore, the water in the tube isn't cold but rather it's warm, at least, and one can rely on the many authorities who hold that lach (something with fluid) cannot be re-cooked (אין בישול אחר בישול בלח). R. Yitzchok Weiss (Minhat Yitzhak vol. 10 §28) is more stringent since he maintained that although many permit water to be re-cooked once it reaches the point of yad soledet (hand recoils from the heat), there is still the opinion of Eglei Tal that water must first reach the bubbling point to be considered cooked. Likewise, he suggests that a person is concerned with the water that is released into the vessel (ניחא ליה).
  2. Pulling the spigot and causing some water from the tube to be released into the vessel is only an act of gerama (causation), which is rabbinically prohibited, and therefore permitted here, vis-a-vis #1, where we are dealing with a rabbinic-level issue altogether. (R. Weiss, ibid., neglects to deal with this factor.)

R. Yosef also cites R. SZ Auerbach (Minhat Shlomo vol. 2 §34:23) who, in agreement with the first two issues and R. Yosef's position, writes that after investigation found the water in the tube to be almost the same temperature as the water in the vessel and therefore does not present any problem of being re-cooked.

R. Yosef further cites R. Binyamin Zilber (author of Az Nidberu) who permitted usage of this urn, as well as R. Abba Shaul (ref. by @Shoel U'Meishiv).

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