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Color in Drinking Water

Water Contaminants: Color
Published on 12/30/2016

People are naturally uneasy about drinking water that has a strange color. Many different factors can cause water to have color. Even pure water appears blue when light passes far enough through it because it absorbs light from the red end of the color spectrum.

“A number of factors can cause color in water, usually due to the presence of dissolved material or suspended solids.”

Milky-white or hazy water is usually caused by harmless air bubbles in the water. To test this, pour water into a clear glass. If the color is due to air, it should start to clear up within 2 to 3 minutes, starting from the bottom of the glass.

A number of other factors can cause color in water, usually due to the presence of dissolved material or suspended solids. A brownish, tea-like color can come from dissolved tannins produced by decaying plants, and similar yellow or brown colors can come from other dissolved organics, humus and peat. Algae and phytoplankton can cause the water to be green. Runoff from eroding soil can contribute clay and silt particles that make water yellow, brown, red or gray. A brown, rusty color usually comes from rust in water pipes, and corrosion of copper pipes can cause blue-green color in water.

Color and Human Health

Color by itself is not toxic and does not pose a health concern. Color is listed as a secondary water quality characteristic by the U.S. Environmental Protection Agency (USEPA). Secondary drinking water standards are for factors that may cause cosmetic or aesthetic effects rather than health concerns. The USEPA standard for color in drinking water is 15 color units, which is enough to give a noticeable tint to the water.

Diagnosing Color in Drinking Water

“Coloring of water due to copper can indicate contamination by other metals associated with corrosion of pipes, such as lead.”

The following table can help diagnose the source of color in your water.




May stain sinks or discolor laundry


Dissolved natural organic matter

Possible sources include marshes or wetlands



Not a health concern



* Excessive copper concentrations can cause vomiting, diarrhea or other problems with the digestive system

* Can indicate contamination by other metals associated with corrosion of pipes, such as lead

* Corrosion of pipes can damage plumbing

Milky white

Air bubbles or precipitated solids

Refer to the text above for how to test for air bubbles.

If the cloudiness does not go away when water stands for a few minutes, it could be due to precipitates formed in heated water. This can be treated by flushing the water heater periodically.


How to Remove Color from Drinking Water

If the color is from iron or copper, treatment methods designed for those contaminants should be used. There are many possible causes of iron in water, and the treatment method depends on the source. The presence of copper in drinking water may be due to acidic water, which can be treated using an acid-neutralizing filter or a soda ash chemical feed where the water enters the house. Otherwise, color can usually be removed from drinking water by granulated activated carbon (GAC) filters.

Granulated activated carbon (GAC) filters are simple to use and relatively inexpensive. They remove contaminants that stick to small particles of material such as coal or charcoal. These filters can take the form of point-of-use systems (such as at a kitchen sink) or pitchers manually filled with water. GAC filters should be replaced or regenerated periodically to maintain their effectiveness.