Think it's probably closer to 60 at my house. I use bleach and rinse alot. As far as actual beer water, I probably don't use much over 5 gallons. How much can I possibly lose in an extract boil?
I use about 5.25 gallons for actual beer water. 20-40 sounds about right for cleaning/sanitizing. And that's just on brew day...that's not counting bottling day...etc.