Frequent Questions

Why do water systems add phosphate to drinking water? What are the health effects of drinking water containing phosphates.

Public water systems (PWSs) commonly add phosphates to the drinking water as a corrosion inhibitor to prevent the leaching of lead and copper from pipes and fixtures. Inorganic phosphates (e.g., phosphoric acid, zinc phosphate, and sodium phosphate) are added to the water to create orthophosphate, which forms a protective coating of insoluble mineral scale on the inside of service lines and household plumbing. The coating serves as a liner that keeps corrosion elements in water from dissolving some of the metal in the drinking water. As a result, lead and copper levels in the water will remain low. The key to ensuring that orthophosphate reduces lead and copper levels, is for PWSs to maintain proper orthophosphate levels.

The health effects of drinking water with phosphates are not known. The Food and Drug Administration (FDA) has issued a report on the toxicology of inorganic phosphates as food ingredients. The FDA considers phosphates as a food additive to be "generally recognized as safe." This report is available at: Also, NSF International maintains recommended maximum dosages of drinking water additives including phosphate products. The typical phosphate levels found in a liter of drinking water are about one hundred times lower then the phosphate levels found in the average American diet. For example, a person would have to drink ten to fifteen liters of water to equal the amount of phosphates in just one can of soda.

People concerned about their health and phosphates added as a corrosion inhibitor to the drinking water, should contact their medical care provider.

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