We continue with our Erev Shabbos-Hilchos Shabbos Series:

1.    Our custom is to treat a Dovor Gush (a solid food item which is 110 degrees and above) with all of the restrictions of a Kli Rishon for most practical purposes--even if it is in a Kli Shlishi.  Therefore, one may not sprinkle garlic, celery, diced onion, or any previously uncooked spices and seasoning directly onto a hot Dovor Gush, just as one may not put these items into a Kli Rishon.  (The 39 Melochos of Shabbos by Rabbi Dovid Ribiat, Shlita, p. 583)

2.    It is permitted to wash dishes using hot water that was heated before Shabbos.  However, care must be taken not to pour the hot water directly onto the dirty dishes, as this can cause bishul of the food residue left on the dishes.  The correct procedure is to first pour the hot kettle water into a large cup or container (i.e., a Kli Sheni), and then to transfer this hot water into an empty wash basin.  The dishes may then be put into the basin, which is now a Kli Shlishi.  Liquid Shabbos soap may then be added.  Note that dishes may only be washed on Shabbos if needed later on Shabbos (ibid., 641-642).

3.    If the hot water faucet was accidentally turned on (or left running) on Shabbos, there may be a problem with turning it off, as shutting the faucet may cause cold water remaining in the tank to become hot and cook.  If one is uncertain as to how his hot water/heating system works, or how his cold water is being heated, he may apprise a non-Jew of the problem in the hope that he will understand on his own that his services are needed to shut the water (if possible, the Non-Jew should not be instructed directly to shut the water) (ibid.).