We can drink distilled water. Distilled water is more clean and pure than ordinary water. But the adverse effect is that it does not contain essential minerals.
Distilled water of good quality may have pH value between 7.0 and 6.7 since it absorbs carbon dioxide from air and becomes acidic. Distilled water of low pH like 5.5 is not good for drinking purpose. But we can drink distilled water having pH closer to 7.