Quality water is safe water, but what does “water quality” mean? According to the US Geological Survey, water quality can be thought of as a measure of the suitability of water for a particular use based on selected physical, chemical, and biological characteristics. Drinking water is a necessity to sustain life; its quality varies from place to place but it ultimately must meet certain water quality standards such as the Philippine National Standards for Drinking Water (PNSDW) to ensure that it is free from harmful contaminants and is safe for public consumption.