Hot Shower on shabbos


Does it depend on how hot the water gets and/or if I live in an apartment building?


There are two issues with showering on Shabbat.

  1. Bishul - heating up or causing water to be heated up.
  2. A Rabbinic gezera of bathing on Shabbat.

If the boiler is set below Yad Soledet - 130°F then there’s no Bishul problem.

If the bathing is not for pleasure (you’re uncomfortable because you’re sweaty…) then there’s no gezera by mitztaer

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Are there issues with a woman and hair, and with drying with a towel (i.e. squeezing dry)?

No problem

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I wanted to determine how hot my boiler gets, if when I measure the hot water coming out of the tap at 120, can I assume that it doesn’t get hotter than 130F?

No you need to measure the temp at the hot water where there is a release valve

Does this still apply if the building is owned and operated by non-Jews?

No difference. You cant cook water on Shabbat even if its not your water.

Can one take a shower on yom tov without the water being less that yad soledet?

Yes but the shower should just be at a comfortable temperature to clean yourself. Not to sit and enjoy a hot shower

The way I understand hot water boilers work is : You set a temperature and the boiler’s heating element goes on full blast (higher than Yad Soledet) to heat the water adjacent to the heating element to a high temperature. As the newly heated water mixes in with the rest of the water, eventually the average temperature measured by the thermostat at a point far away from the actual heating element reaches the desired temperature and then the thermostat signals for the heating element to turn off. If this is the case, then even setting the temperature to below Yad Soledet would cause Bishul of the water adjacent to the heating element and should be a problem.

The concern isn’t what will happen to the water next to the heating element. The main concern is the new water entering the boiler. We don’t want to cook that water.