This article focuses on the internal corrosion of iron and copper in potable water as these are still the prevalent materials. It tabulates the corrosion and water-quality problems caused by materials in contact with drinking water. The article provides a theoretical description of reduction-oxidation reactions in water to analyze the causes of corrosion of metals in contact with water. It discusses the Langelier saturation index and the Larson index for determining corrosion in potable water systems. The article describes the two major ways of mitigation against corrosion in potable water systems. The first way is to line the pipe surface physically such that water and dissolved oxygen cannot reach the metal surface and the second way is to add chemical inhibitors to alter water chemistry.