Halacha Date: 25 Iyar 5771 May 29 2011
Answer: We have previously established that although Yom Tov is equal to Shabbat regarding the prohibition of work, nevertheless, there are some forms of work which may be performed on Yom Tov, provided that they are works are enjoyable by all. Thus, one may cook something on Yom Tov to be eaten on Yom Tov itself, as long as he does not create a new fire on Yom Tov, rather, he should use a flame from a pre-existing fire.
Additionally, one may light a bonfire on Yom Tov in order to use it for warmth during the cold season, since this is considered an “enjoyment equal to all” (meaning everyone enjoys such a thing), as all indeed require warmth (once again, provided that one does not create a new fire, rather, only transfers a flame from a pre-existing fire.)
For the same reason, one may heat water on Yom Tov (using an electric/gas boiler that was already turned on from before sunset on Erev Yom Tov) in order to wash his face, hands, and feet, for this too is considered an “enjoyment equal to all.” However, one may not heat water on Yom Tov in order to wash his entire body, for washing one’s entire body daily is not considered an “enjoyment equal to all.”
Nevertheless, since the only prohibition involved here is regarding the way the water is heated on Yom Tov whereas the actual act of washing one’s entire body with hot water is not forbidden, one may indeed wash his whole body on Yom Tov with water that was heated before Yom Tov (i.e. before sunset on Erev Yom Tov), as our Sages did not ban this on Yom Tov as they did on Shabbat. Similarly, water that was heated through a solar heating tank (a.k.a. “Dud Shemesh,” common in Israel) on Yom Tov itself may be used to wash one’s entire body on Yom Tov. (All this applies only in one’s private shower at home, however, regarding a public shower room, such as in a dormitory where there are several shower stalls, one may not use the hot water from these showers even to wash his face, hands, and feet, for our Sages forbade washing with hot water in public places since the public bathhouse attendants would act derisively and heat up the water in forbidden ways.)
Summary: One may wash his entire body on Yom Tov either with water that was heated through an electric/gas boiler before the onset of Yom Tov or with water heated in a solar heating tank even on Yom Tov. This only applies, however, to one’s private shower at home. Nevertheless, water that was heated on Yom Tov itself through an electric/gas boiler that was turned on before the onset of Yom Tov yet continues to operate on Yom Tov may not be used to wash one’s entire body; however, one may use this water to wash his face, hands, and feet.
By popular request: Regarding water that was heated in an electric/gas boiler before the start of Yom Tov and the boiler continues to work on Yom Tov, causing the water to retain its heat, is it permissible to use this water on Yom Tov?
We have posed this question to Maran Harav Ovadia Yosef Shlit”a and his response was that if the water was heated well before the onset of Yom Tov and the boiler’s operation on Yom Tov serves only to retain the water’s heat but not to reheat it, one may use this water to wash his entire body on Yom Tov.
Nevertheless, one must take care that no new water enter the hot-water tank, for if so, by showering one is causing the new water entering the tank to be cooked. Thus, the only way it will be permissible to shower on Yom Tov (using water from an electric/gas boiler) is only if the cold-water valve, through which new water enters the hot-water tank, is shut. However, if one does not shut the cold-water valve, it seems there is no room for leniency in this matter.