Which substance can lead to discolored water in distribution systems?

The presence of iron in distribution systems is notorious for causing discolored water. When iron is oxidized or disturbed, it can release particles into the water supply, resulting in a reddish-brown hue. This is often noticeable in areas where the water has been stagnant in pipes or where rusting of iron pipes has occurred. The aesthetic quality of water is significantly affected by iron, even if it is not harmful to health at typical concentrations.

While calcium, copper, and lead can also interact with water systems, they tend to cause different issues. Calcium may lead to hardness and scaling, copper can cause a blue-green tint and is more associated with corrosion of copper pipes, and lead is primarily a health hazard rather than a cause of discoloration. Iron, specifically, is recognized for its direct impact on the visual clarity of drinking water, making it the most relevant choice for this question.