Texas Commission on Environmental Quality (TCEQ). Class C Water License Exam

Red water or red stains in water are typically caused by high levels of which substance?

1. Chlorine

2. Iron

3. Manganese

4. Sulfate

The correct answer is: Iron

Red water or red stains in water are predominantly caused by high levels of iron. Iron is a common element found in soil and rocks, and when it dissolves in water, it can create a reddish tint. This is particularly noticeable when water is oxidized, which can occur when water enters the distribution system or when it is exposed to air. As iron oxidizes, it forms iron oxide, commonly known as rust, which contributes to the red coloration. When assessing water quality issues, it's important to recognize that iron can also contribute to other problems, such as staining of laundry and fixtures, as well as imparting an unpleasant metallic taste to drinking water. High concentrations of iron can also interfere with disinfection processes and create challenges for water treatment systems. In contrast, while chlorine can create a range of other water quality concerns, it does not typically cause red coloration. Manganese can contribute to dark brown or black stains but is not associated with red water. Sulfate generally does not impart any color to water in the same way iron does. Therefore, recognizing iron as the primary culprit behind red water is essential for effective water treatment and management.