This is an issue that mostly occurs with hard (heavily mineralized) water. The healthiest water has a higher PH level because it has less acidity. When the PH level of the purified water is raised, the acidity of the water goes down and the water is no longer able to hold as many minerals in solution.  When this happens the minerals begin to precipitate out over time and,  depending on the mineral composition,  they will either sink to the bottom or float to the top.  This process is known as flocculation and the precipitated minerals are usually referred to as “white floaters”.  The bottom line is that this is nothing to be concerned about. The white floaters are minerals that were already in your water; they are now simply visible whereas they were previously invisible due to their suspension in an ionic form.