Jan 11, 2019
Using a Hot Water Urn on Shabbos

Question for the Rabbi: May we use an urn for hot water on Shabbos with an external water level indicator?

Answer by Rabbi Chaim Hillel Raskin - Rov in Kfar Chabad Beis, Israel:

When one releases water from such an urn, some water exits the tube and mixes into the main water chamber which is kept at a higher temperature. The question is whether doing so is considered cooking on Shabbos.

Halacha states that cold liquids—in contrast to dry solids—are subject to the Shabbos prohibition of cooking even after they were already completely cooked (yesh bishul achar bishul b'lach).

If, however, the liquid was completely cooked and is still appreciably warm (i.e. around 86° for illustrative purposes), heating it further is not prohibited—according to the Rema and Alter Rebbe—for it is viewed by halacha as "warming" as opposed to "cooking."
While some poskim restrict one from bringing it to a boil, the Alter Rebbe implies that this is permissible.

Thus, if a pot of soup is on the blech where it is at least that temperature and all its contents are completely cooked, one may move it closer to the flame where it will begin to boil.

At what point are liquids considered fully cooked? Some poskim hold only once they were boiled; otherwise, even if they are very hot, one may not heat them further.

Others hold they are cooked once they have reached the heat of yad soledes bo (the upper bracket being 160°-174° F). The Alter Rebbe appears to side like this latter opinion, and so rule many contemporary halachic authorities.

When it comes to the urn, the water in the tube is estimated to be several degrees less than the primary water chamber. Yet, since that water definitely reached the heat of yad soledes when the urn initially boiled, and it is still at least warm, there is no concern when that water heats up more as it mixes with the hot water inside the urn.
Moreover, some claim that according to the laws of physics, hot and cold water that are touching will always mix between themselves, causing the heat to be distributed relatively evenly.

A halachic advantage of having this tube is so that one has advance warning before emptying the urn completely, thereby either causing the machine to shut off automatically or to burn out (and perhaps lead someone to add cold water).

Originally published in the Weekly Farbrengen, a newsletter by Merkaz Anash. See Sources

Most Read Most Comments

Opinions and Comments
good to get halacha here!
maybe you can post the full details about a crock pots and blech, on Shabbos and a warming drawer.
(1/11/2019 12:32:42 PM)
is there an issue of measuring?
(1/11/2019 12:39:25 PM)
Filling Urn before shabbos
Please reply:
Can one plug in an urn filled with cold water at licht bentchen?

(Does the water in urn need to be cooked/hot before shabbos?)

PLEASE REPLY HERE!!!!!!!!!!!!!!!!!
(1/11/2019 1:55:53 PM)
To #3
No you cannot
(1/11/2019 2:30:45 PM)
#3 yes you can
Unless it has a dial which you could turn up on Shabbos to make it boil quicker, it is OK.
(1/11/2019 3:22:44 PM)
to 3
yes has to be cooked before shabat but not up to 212f.
if gets to around 110 farenheit it's fine.
remember that you have the 18 min that if the urn is small they will be hot enough when comes shkiah
(1/11/2019 3:29:52 PM)
To #4
Please cite your source for that. A Shabbos urn with no buttons has the status of Garuf V’Katum.
(1/11/2019 3:38:47 PM)
Urn erev shabbos
Yes you can. It has to be fully cooked or raw/uncooked before Shabbos.
(1/12/2019 11:27:14 AM)
hot and Cold Water Mixing
"Moreover, some claim that according to the laws of physics, hot and cold water that are touching will always mix between themselves, causing the heat to be distributed relatively evenly."

In that case, how can the bor al gabei bor mikva work?
(1/12/2019 3:28:16 PM)
Here is the Solution
If you put a piece of scotch tape on the little hole on top of the exterior glass tube then no water goes into the actual percolator. I read it in the four volume series on laws of shabbos. Whenever I go to a hotel shabbos weekend program I check to see what type of perculator the caterer put out and if need be slip a tape over the little hole on the exterior glass indicator.
(1/12/2019 5:51:49 PM)
4 opinions on question of #3!!!
Definitely yes. Definitely no. Partial
Please get a definitive answer posted!!!
(1/12/2019 5:56:21 PM)
Shabbat prohibitions
So how did Jews in ancient times keep their water hot, I wonder. Or did they just drink cold? Yesterday's answers do not necessarily fit today's questions in this highly technological and digital age.

(1/12/2019 6:09:08 PM)
In the olden times before urns and Keurigs we had kettles. Chainiks. We put one on the blech before Shabbos and had hot water on Shabbos.
(1/12/2019 7:06:34 PM)
Anonymous poskim in the comments are not so helpful.
(1/12/2019 9:28:33 PM)
question was asked to rabbi schwei
This question was asked to rabbi schwei. He said the water should be boiled before shabbos. Also he said to tell the goyish workers in 770 not to add more water to the urn on shabbos
(1/13/2019 8:56:24 AM)
To #15: Please clarify!!
Did the rabbi say "the water SHOULD be boiled before shabbos" (meaning l'chatchila it is better that the water be boiled before shabbos), or did he say, "the water MUST be boiled before shabbos" (meaning that if it was not boiled before shabbos - it cannot be used!)????
(1/13/2019 3:55:31 PM)
The following is Psak of a senior Chabad Rov
L'chatchilah the water temperature in the urn should reach 45 degrees Celcius (113 degrees Fahrenheit) by shkiyah. (This gives deference to Reb Moshe Feinstein's psak that water should be boiled before shabbos - as such it is "boiled" at yad tzoledes bo). Usually, with most urns, this is easily reached in approx 20 minutes, if one fills the urn just prior to licht tzinden till shkiyah. This is "the best" practice l'chatchila!

B'di'eved, if one forgot and simply filled the urn closer to zaman of shkiyah - it is 100% perfectly ok to use the water (only) AFTER it is fully cooked water on shabbos. This is the ruling of major poskim such as Reb Shlomo Zalman Aurebach that all agree it is MUTTAR!

Indeed Reb Shlomo Zalman Aurebach commented on Reb Moshe's psak (requiring that water be boiled before shabbos) that this is merely a "zihirus b'almah" (just being "extra careful" - preferred, to prevent the ability of someone mistakenly using the water before it is fully boiled), but not a requirement.

This is also the accepted practice of Anshei Yerushalayim and has been the practice of Yidden since ancient times.
(1/14/2019 4:09:26 PM)
Two rabbis - 2 opinions
So #15 says that Rabbi Schwei said the water "should" be boiled before shabbos (and not clear if should means it must or it is better,,,)

While #17 says that Senior Chabad Rov (local or international) says that best to have water warm by shkiya (113 degrees) but if not, it is ok, even cold - but caution not to use water till it is fully boiled...

Can a third opinion settle this REAL question!!!!
(1/14/2019 9:50:35 PM)
On Line Rov

Heating the water before Shabbos:[6] In all cases[7], the water in the electric urn must be heated to half its heat [i.e. to at least 50 Celsius/122 Fahrenheit[8]] before Shabbos [sunset[9]] begins, and hence one must make sure to set it up and turn it on with enough time before sunset for it to heat up to this amount.
(1/14/2019 9:53:35 PM)
Hot and Cold mixing
To #9:
The concept referred to is known as "tata'ah gavar" ("what's on the bottom has precedence). It's not about the actual mixing involved, but rather when they are mixed, the resulting temperature is in the middle.

For example, (this is described in great detail in Shulchan Aruch ch 318, if memory serves) pouring cold water onto a bunch of hot water is assur (when the hot water is at least half of the amount of cold water that you wanna pour), since the bottom is hot, and thus is stronger in its affect.

However if you want to pour hot water into (at least as much) cold water, that's fine since in the end you're only "cooling down" the hot water.

Here too, when a bit of hot water pours into water of lesser heat in the chamber, it would seem to be OK.
(1/21/2019 1:41:15 AM)
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