i may have read this in palmer, maybe saw it on here somewhere but it seems a little useless to me, i mean kitchens clean food cooking equipment with unboiled water, why would we have to? little info please?
I've never heard of this personally. I know Iodophor for example works best in cool water, not warm water so you are right, it would make no sense. I've only heard of boiling water you're going to top off with, which makes total sense.
What about if there is lots of chlorine in the water? Would mixing the sanitizer not make the chlorine be able to give off flavors to the beer? I don't know if it takes a lot or a little to give off flavors.
The chlorine itself can give off flavors, but it won't interact with the sanitizers we use for brewing. Boiling the water would drive off chlorine, but not chloramine which is what many water treatment plants use for sanitation. For that, add a tablet of campden to your water.
I've always used unboiled tap water to top off as well. It really depends on the cleanliness of your local water supply. Your city should have available documention on both water characteristics and cleanliness.