The ONLY way to be sure your diluting water is free of any chemicals (especially chlorine) is to use steam-distilled water. It's available at any supermarket or discount drug chain and costs less than $2. for a gallon. Since a gallon contains 128 ounces, and the shot-glass dilution method uses 1.5 ounces each time, that gallon will last you all summer.

What's the big deal? $2 for the proper distilled water is less than one gallon of ultra bleach.