why do people boil cold water and not hot water?

If your home is equipped with a water softener, the water softener is generally attached to the hot water line. Thus, the hot water line has various "salts" added to the water. And if you want "pure" water, you'd use the "cold" line and then boil that water.

If you don't have (or need) a water softener, there is no difference between the hot and cold lines. We do not have a water softener. If we need to boil some water, we always take it from the hot line, which is pre-heated, and thus our water boils faster!

We should clean the hot water tank once in a while. Almost everybody does not!

When you empty the tank the water at the bottom is pitch black.

So for making a drink it is much safer and probably healthier to use cold water.

You might find some interesting story here

http://www.askthebuilder.com/045_Hot_Water_Heater_...

http://www.google.ca/search?hl=en&q=why+does+hot+w...

Hope this properly answers your question

Guru

something to do with the difference betwixt the molecules in cold water and hot water

boiling makes things hot.

why would you want to make something hot that already is hot?