Originally Posted by poppalarge
Apologies if this has been asked a million times.
Is it safe to 'top off' with tap water?
If so, why can't I dump tap water in to chill my wort?
Yes, I've done it. But you don't want to use water with chlorine or chloramines, as that will ruin the taste of the beer. (When fermentation occurs with chlorinated water, bad off-flavors called chlorophenols result).
I always had great tap water, and used it often to top off and to help chill the wort.
When chilling the wort, though, you still have to chill the wort in the boil kettle to under 90 degrees or so. That's because if you have, say, 2.5 gallons of boiling hot wort, 2.5 gallons of cold water will not chill it enough. Then you'll have 5 gallons of too-warm wort that will take even longer to chill! But if you chill it in an ice bath to 90 or less, and then add 2.5 gallons of 40 degree water, you'd be right at pitching temps!