This was asked by one of my students in my class. I know it is the pH of 7, but others say it can be 6.55 pH
keep in mind that water (distilled, deionized, or tap) is NOT "pure" (i.e., pH equal to 7). The moment it comes in contact with air, CO2 gas begins dissolving into it, forming carbonic acid. The actual pH, therefore, will often be slightly less than 7.