Yep, calibrating solution, same stuff. You should use that to test your pH kit, make sure it's accurate. Your question was whether a reading of 6 was normal for RO water, right? I would say, no that's not normal, plain old water should be close to 7 pH, so maybe your pH kit is not reading correctly. Or am I totally off the mark, and your question wasn't about the pH of the RO water...?? :-P