Q. Is it permitted to use hot water to wash dishes on Yom Tov? Are there any problems of machshirey ochel nefesh?

A. On question1211 we wrote in regards to using hot tap water on Yom Tov from a new type of gas water heater; Horav Shlomo Miller’s Shlit’a opinion is that it is not different than any other water heater that people use on Yom Tov. Poskim (Horav S.Z. Auerbach zt”l – Meor Hashabos 1: p.509, Shemiras Shabbos Kehilchoso 2:7) are lenient for a number of reasons. The lowering of the water temperature by extracting the hot water, is not immediate (grama), nor a certainty, (psik – reisha). On a large tank, taking out a reduced amount of water may not turn on the gas flame at all, it happens by itself anyway, and one does not have intention for it (eino miskaven), besides some heaters have already an existing pilot flame on, therefore many are lenient and use the hot water on Yom Tov.
Washing dishes on Yom Tov when needed for that day is therefore permitted. (Rema O.H. 511: 2, see Shemiras Shabbos Keh. 12: 5: n. 14).

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a