In a water distribution system, red water is an indication of what problem?

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Red water in a distribution system points to iron-related corrosion products entering the water. The reddish tint comes from iron oxides and hydroxides that are released when iron or steel pipes, fittings, or service lines corrode or when sediments in the mains are disturbed by flushing or high flow. This discoloration is a visual cue that iron particles are present, not a direct signal of chlorine residual or low pH by itself. If the red color persists, it suggests ongoing corrosion or sediment release and may prompt investigation of the corrosion-control program (such as adjusting pH/alkalinity or adding inhibitors) and targeted flushing or pipe replacement.