“Red water” describes any situation where water takes on a red, yellow, orange, or brownish hue. This discoloration can occur in household tap water or in large natural bodies of water like lakes and oceans. While often startling, red water signals different underlying issues depending on where it is found. The phenomenon is a concern for both water quality in homes and the ecological balance of natural environments.
Sources of Red Tap Water
The most frequent cause of red or brown water flowing from a home’s faucet is the presence of iron from corrosion within the water supply lines. Many older homes and municipal water systems use pipes made of iron or galvanized steel. Over time, these pipes can rust, and the iron oxide particles can flake off and mix with the water, giving it a distinct rusty color.
Physical disturbances in the water distribution system are another common trigger. Nearby construction, firefighting activities that require opening hydrants, or routine flushing of water mains can all increase the speed and change the direction of water flow. This abrupt change can stir up settled sediments, including iron and manganese particles, leading to temporary discoloration.
For homes with private well systems, red water can indicate high concentrations of iron in the groundwater. In these cases, the water might come out clear but turn reddish-orange after being exposed to oxygen, a process called oxidation. The issue could also be isolated to a home’s hot water heater. Corrosion of the tank or a failing anode rod can release rust particles, causing only the hot water to appear discolored.
Causes of Reddened Natural Waters
In natural settings, red discoloration is caused by biological or environmental events. The most well-known cause is a harmful algal bloom (HAB), often called a “red tide.” These blooms occur when microscopic algae grow so rapidly that they visibly color the water. Favorable conditions like warm water temperatures and an influx of nutrients from land runoff can fuel these growths.
Sediment runoff is another primary cause of reddened natural waters. Following heavy rainfall, soil, clay, and silt from surrounding land can be washed into rivers and lakes, making them appear brown or red. This is common in areas with significant land development or agriculture, where erosion can be more pronounced.
A different process involves tannins, organic compounds released from decaying vegetation. When leaves and wood break down near a body of water, they can leach tannins, staining the water a tea-like brown or reddish color. This is a common and harmless occurrence in forested wetlands. Less frequently, industrial pollution or chemical spills can also cause discoloration.
Understanding Red Water Risks
The risks of red water differ between tap water and natural water bodies. For household tap water, discoloration from iron rust is primarily an aesthetic issue. While the water may have an unpleasant metallic taste and can stain laundry and plumbing fixtures, it is not considered a direct health hazard. The EPA classifies iron as a secondary contaminant, monitored for cosmetic and technical reasons, not for posing a health threat.
Conversely, red water in natural environments can signal danger. Harmful algal blooms can produce potent neurotoxins that accumulate in shellfish, making them poisonous to humans who consume them. Direct contact with or inhaling aerosols from this water can cause respiratory irritation and skin rashes. Additionally, water heavy with sediment can reduce visibility for recreation and may carry other pollutants or pathogens from the land.
Responding to Red Water
When encountering red tap water, run a cold water tap for several minutes to see if the discoloration flushes out. If the water clears, the issue was likely a temporary sediment disturbance in the mains. If the problem persists, affects all taps, or only occurs with hot water, it points to an issue with the home’s plumbing and a licensed plumber should be contacted. For recurring problems with municipal water, notify the local water utility.
For reddened natural waters, avoid swimming, fishing, or harvesting seafood in areas with visible algal blooms or discolored water. Public health departments or environmental agencies often issue advisories or beach closures during these events, so check these resources before recreational activities. Reporting observations to park services or environmental authorities can help them monitor the situation.