Water pH really isn't very important. What is important is alkalinity. Either get the alkalinity number from your supplier or send a sample off to Ward Labs. Unless you are one of the fortunate few with very low alkalinity water the simplest approach is to dilute the water you have with low ion content (DI,RO) water until the alkalinity is low. Then follow the guidance in the Primer in the Stickies and step off from there as your experience increases.