@Dabber like they said, depending on your starting water and desired pH will determine if you need to make adjustments. When we were testing the pH balance we asked friends around the country to send us some of their tap/well water and found that with most water types the pH ends up between 5.8-6.3. Using RO the pH will be closer to 5.8 and as the hardness of your water increases the final pH will be higher. If you have very hard water then you can get a final pH higher like
@Dichoti has. Once you start mixing you sill see where your feed ends up and it should be consistent from batch to batch in the res.