Seasonal Variations in the Taste of Drinking Water

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The Town of Cary’s water source is Jordan Lake, a large reservoir located approximately 10 miles west of Cary in eastern Chatham County. Like many large bodies of water, Jordan Lake is influenced by environmental factors and undergoes seasonal variations caused by factors such as temperature, available sunlight, rainfall and runoff. These seasonal variations in environmental conditions can lead to fluctuations in naturally occurring algae and algal activity.

Commonly occurring algae in Jordan Lake can impact water quality in a variety of ways. One way algal impacts are most notable to water customers is unpleasant taste and odor. Under certain seasonal environmental conditions, algae in Jordan Lake can release taste and odor compounds into the water that have the potential to be noticed at the customer’s tap. Customers typically characterize the unpleasant taste and odor as “earthy," “musty," or “dirty.” These variations most commonly occur in the early spring and fall time periods.

We typically get several questions from Town customers during times when algal induced taste and odor is greatest in Jordan Lake. Following are answers to some of the frequently asked questions regarding this issue:

Is the water safe to drink?
Yes. The taste and odor is purely an aesthetic issue. The Town's water remains completely safe to drink and use for all purposes. All of our drinking water continues to surpass all regulatory standards for safety.

What causes the taste and odor?
Seasonal variations cause algae in our source water (Jordan Lake) to release unpleasant taste and odor compounds. These compounds are naturally occurring and not harmful to people. They are released to the water in extremely tiny quantities (nanograms/Liter or parts per trillion), but for those with sensitive noses and palates their arrival is quite obvious. The reason for the release can be due to several factors, including:

  • Significant increases in algae levels, or commonly known as an algal bloom
  • Change in algae types from those that do not produce taste and odor compounds to those that do 
  • A die-off of certain types of algae due to seasonal variations in water temperature or sunlight availability or other environmental conditions
  • Seasonal turnover of the lake water column in the fall when the surface water cools and settles and remixes with water containing low oxygen from the deep regions in the lake  

What steps does the Town of Cary take to control the taste and odor?
It is our goal to produce high quality drinking water that is not only safe to drink but is aesthetically pleasing as well. We closely monitor our source water for algae and taste and odor compounds and utilize treatment techniques such as activated carbon adsorption and advanced oxidation by ozone to minimize the unpleasant taste and odors. However at times, levels of taste and odor compounds can be high enough that our water treatment processes cannot remove 100% of the unpleasant taste and odor from our finished drinking water.

The Town installed an intake aeration system in 2017 and we continually plan for additional upgrades to the Cary/Apex Water Treatment Facility that will further reduce the frequency of taste and odors detected by our customers.

How long will the taste and odor last?
The length of historical taste and odor episodes has typically been for just a few weeks in duration. While treatment for taste and odor in our source water is a routine part of the normal water treatment process, the peak periods where customers may notice this condition is generally only for a few days or up to a couple weeks. The time it takes for the taste and odor of the water to improve varies from household to household and is impacted by the fact that our drinking water has to work its way through the water distribution system, which contains over 900 miles of water lines, before it is delivered to your home. While the taste and odor may be completely removed and water restored to normal at the water treatment plant, it may take several days for these improvements to reach customers across town.

What steps can be taken at home by customers to minimize the taste and odor? Some customers have reported improved taste and odor by adding a lemon wedge to a refrigerated open pitcher of drinking water. Additionally, standard home water filtration systems that contain fresh carbon may help to mitigate the taste and odor of these substances.

We encourage our customers to contact us with any questions or to report any concerns.


Town of Cary
311 or (919) 469-4090

For more information about annual water quality of the Town’s drinking water:

For information about changes at the tap during March of each year:

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