Science, Tech, Math › Science What Is the pH of Water, and Why Does It Matter? Share Flipboard Email Print Michael Heim / EyeEm / Getty Images Science Chemistry Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated October 20, 2019 At 25 C, the pH of pure water is very close to 7. Acids have a pH less than 7, while bases have a pH higher than 7. Because it has a pH of 7, water is considered to be neutral. It is neither an acid nor a base but is the reference point for acids and bases. Is Water Basic or Acidic? The chemical formula for water usually is written as H2O, but another way to consider the formula is HOH, where a positively charged hydrogen ion (H+) is bonded to a negatively charged hydroxide ion (OH -). This means water has properties of both an acid and a base, where the properties essentially cancel each other out. H+ + (OH)- = HOH = H2O = water The pH of Drinking Water Although the pH of pure water is 7, drinking water and natural water exhibits a pH range because it contains dissolved minerals and gases. Surface waters typically range from pH 6.5 to 8.5, while groundwater ranges from pH 6 to 8.5. Water with a pH less than 6.5 is considered acidic. This water typically is corrosive and soft. It may contain metal ions, such as copper, iron, lead, manganese, and zinc. The metal ions may be toxic, may produce a metallic taste, and can stain fixtures and fabrics. The low pH can damage metal pipes and fixtures. Water with a pH higher than 8.5 is considered basic or alkaline. This water often is hard water, containing ions that can form scale deposits in pipes and contribute an alkali taste.