Nice... We share the same water.
What I've been doing for 5 gallon BIAB batches for a typical beer is 5 US gallons of RO water (I get mine at CO-OP for $2. Canadian tire has the refill stations too for a little bit cheaper) and 3.x gallons of tap water. Then I add 5 or 6 grams of CaCl2 to get...