The pH level of most reverse-osmosis-treated water ranges from 6.5 to 8.0. The exact pH level depends on the age and condition of the filtering system and the composition of the source water. Water with a pH below 6.5 are considered acidic, while water rating over 8.0 are alkaline.
When water has an acidic pH level, it has a metallic taste and may contain higher amounts of copper or lead, depending on the type of pipes and fixtures used in the plumbing system. Adding a mineralizng filter to the reverse-osmosis system neutralizes the pH level and removes the metallic taste. Environmental Protection Agency regulations require drinking water to maintain a pH value of 6.5 to 8.5.