Color in water supply should be less than ______ units?

• A. 10 units
• B. 15 units
• C. 20 units
• D. 25 units

Answer: (B)

Color is an aesthetic water quality parameter that tells us how clear or discolored the water appears, often due to dissolved organic matter. In drinking water, the commonly cited guideline is to keep color below 15 color units (CU) because that level generally yields clear water with acceptable taste and appearance. The 15 CU target comes from the EPA’s secondary maximum contaminant level for color, focusing on consumer acceptability rather than safety.

So, the best completion is fifteen units. Values up to 15 CU are typically considered acceptable, while higher values indicate noticeable coloration and may signal the need for treatment steps like coagulation, filtration, or activated carbon to remove color.