Water Color Odor Appearance and Taste
Your First Evidence of a Problem


Secondary Water Quality Issues

algal, bacteria, fecal coliform, e_coli, contaminated water, slime bacteria, water color, odor, trihalomethanes   environmental monitoring, remote monitoring, water quality, water testing, watershed monitoring




Is your water safe to drink? Does it smell funny or is it cloudy or off-color?  The increase in the reported cases of  chemical spills, leaking oil tanks, toxic waste sites, and pesticide use may make you wonder about the quality and safety of your water.

what is in your water. Whether you get your water from a public or a privately-owned public water system, or your own well or spring, having a safe source of drinking water is vital to the health of you and your family.  

Changes in the appearance, taste, odor, and color may be your first evidence of a problem. Color in water can be caused by a number of contaminants such as iron which changes in the presence of oxygen to yellow or red sediment. Color from iron is referred to as "apparent color" rather than "true color". True color is distinguished from apparent color by filtering the sample.


The most common source of true color is decaying organic matter such as the yellowish "tea color" of water in tundra or wet bogs. True color is mostly found in surface water, although ground water may contain some color if the aquifer flows through a layer of buried vegetation, such as from a long buried slough of a river.


Potential Health Hazards

Color is not a toxic characteristic, but is listed by the EPA as a secondary (aesthetic) parameter affecting the appearance and palatability of the water. When chlorinated, color-causing organic matter may form chlorinated organic compounds such as trihalomethanes. Chloroform is a common trihalomethane, and is along with several others, considered to be a potential carcinogen. For this reason ADEC limits total trihalomethanes (TTHM's) in public water supplies to 0.1 ppm (100 ppb). Color is measured in units based on a platinum-cobalt standard solution which forms a yellow tint and is limited to 15 units in public water supplies.



Color can be removed by activated carbon filters, sometimes marketed as taste and odor filters. The activated carbon or charcoal must be replaced after a period of time when its capacity for adsorption of the color is exhausted. Another treatment method is coagulation and sedimentation using alum or other chemicals. This process is normally used only in large plants since its complexity requires the care of a trained water treatment plant operator.



Color analysis is done by visual comparison to a set of platinum-cobalt standards in Nessler tubes. Sample collection is done in a clean rinsed bottle which should be refrigerated if stored for more than a few hours.

If the color of the water exceeds 15 color units and the water is being chlorinated, we suggest having the water examined for total trihalomethanes by gas chromatography. This is a more expensive and time consuming analysis, but is extremely sensitive with detection limits down to the ppb level. Sample vials specially designed to eliminate the air space above the sample are required for sampling.  For laboratory testing for organics and other chemicals, please visit the Drinking Water Testing Website.

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