Tap water is not as clean as we expect. It may be contaminated during the delivery to our home. The contaminants can be from pipe leakage, pipe repair works or pipe corrosion.
One way to clean the water is to use water purifier/water filter. Nowadays, the most reliable brand is Coway Water Purifier/Water Filter from South Korea.
For more details, please visit http://www.the-coway.com.