I recently attended a homebrew course being run by a local shop ( I like to keep up with things ), the course was very good, but it was suggested that hot water from the kitchen tap could be used in homebrew.
Well as a microbiologist I had to put this one right. If your hot water is fed directly from the mains, and comes out of the tap at mains pressure it is probably safe to use.
However, if you use any form of header tank in the loft to store water and maintain hot water pressure this practice is an absolute no no.
Just image the mice and pigeons in your loft trying to get a drink and falling in and dying. That's what would be going into your food / homebrew / etc. The decaying corpse will provide nutrients to a variety of nasty micro-organisms, and these organisms will flourish in the nice warm sugary solution you are about to provide. Even Legionella sp can live in header tanks.
So, the best practice is still the good old fashioned kettle, but as Pasteur told us - if a wine tastes OK it is probably safe to drink.
By Paul Dowrick