The rule of showering on Shabbat
The following is from the Shulchan Aruch, Orach Chaim – 326
It is forbidden to bath the whole body {on Shabbat}, even limb by limb, even in water which was heated before Shabbat, Their is no difference if the water is in a utensil or on the ground. Even to poor the water on his head and to bathe like that is forbidden. However, it is permitted to wash with such water his face, hands and feet…. All of this refers to water which is heated from fire, but water which is from a hot spring (like that in Tiberius) is permissible to bathe in, even to wash the whole body, We need not even discuss cold water {that is permissible like water from a hot spring}….
- The opinion of Maran, Rabbi Yosef Karo in the Shulchan Aruch is that it is permissible to wash your entire body in Cold water on Shabbat. But only on condition that no hot water is added which has been heated from a fire or from electricity.
- In places where they heat water from solar heaters it is permissible to wash your hands and face with the hot water.
- And so it is permissible to wash your hands and face with water which is preheated before Shabat.
- A boiler which is heated by oil, gas or electricity which lets in cold water when hot water is removed is completely forbidden to use on Shabbat. A solar water heater is permissible to use even tough cold water enters and gets heated.
- In places where water is heated with a solar water heater, even though it is forbidden to wash your entire body in hot water, it is permissible to add a little hot water so that the water will be warm and to wash your entire body with such water.