QUOTE(Pinchas @ Dec 31 2007, 09:06 AM)

What about with hot water heated in a dood shemesh?
I'm not sure exactly how those work, but I'm not sure how that would be different. After all, what's the big difference between that sort of hot water tank and one heated by gas? At the end of the day, the water you are using right now was heated maybe yesterday, but if it's YT day, it was maybe heated this morning, and you use it for ochel nefesh, and new water comes in that you may or may not use later in the day.