Q. If you are staying Shabbos in a hotel, can you use the hot water from the cafeteria that was warmed by the dining-room attendants on Shabbos to make yourself a coffee? What about a Pesach Hotel?
A. See prior question (1012.) Horav Shlomo Miller's Shlit'a opinion is that if the Gentile in charge is unaware that he is boiling water also for an Yisroel, since only a few are attending and they don't stand out, in need it would be permitted.
In a Pesach Hotels one has to ascertain that the water heaters are full and turned on before Shabbos or are on a timer. If there is a cold fresh water intake it should be closed for Shabbos. And no fresh water should be added to the heaters on Shabbos by the attendants.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a