Water discolored from tannins in mangrove roots. / © Adobe Photo
Tannins are naturally occurring chemical compounds, known as polyphenols, found in many plants. They are founds in foods such as wine, tea, and coffee, and help deter animals and insects from eating woody flowering plants. When water passes through decaying vegetation, peaty soil, and other organic materials in the earth, the tannins can be absorbed, giving the water a yellowish or brownish hue.
Tannins are not considered to be a health risk but can still impact your private water well. They are considered a secondary contaminant by the US EPA because they can cause staining, taste, or odor issues.
What are the effects of tannins in well water?
Discoloration – Water will have a yellowish or brownish hue.
Staining – Brown stains in toilets, sinks, tubs, and clothes.
Odor – Earthy or musty.
Taste – Tangy, bitter, or even like tea.
When should I test for tannins in my well water?
If you notice a change in the taste, smell, or color of your water, you should have it tested. To ensure you are protecting your family’s health, we have developed a set of recommendations for testing that are provided in our article, "What do I need to know about sampling my well water?". When testing your well water you will very rarely be testing for only one thing — like color — and instead testing for a suite of constituents that are important to identify if they are in your drinking water.
What treatment should I use if there is tannins in my well water?
Once you test and have decided to treat your water to remove tannins, the Minnesota Department of Health has developed a Home Water Treatment Guide that covers treatment for any common constituent in well water. The most important advice we can provide you is if you are going to add treatment to your home water system, be sure the treatment device has been certified to remove tannins by an independent third-party certification organization.
Where can I get local help and information about tannins in my well water?
Contact your local health department – They can help you interpret your sample results and may have information on the best treatment options for your situation. If they personally aren’t able to answer your questions, they will know who to contact who will be able to help you, likely at your state health department.
Contact a water treatment professional – We would recommend contacting a water treatment professional who has been certified through the Water Quality Association’s Professional Certification Program.
State or Federal Geologic or Water Resource Agency – They may have completed field studies of your area or collected samples from water wells to map and understand the water quality in your state. In addition, they may house water well logs (including yours), or be able to provide additional information about the aquifer your well is getting water from.
Consult your well driller or drilling contractor – The contractor that drilled your well, or other local contractors, may be aware of the water quality issues nearby, including tannins, and might have worked with other well owners in your area to solve this issue.
Research online – You should be inquisitive; it will help you significantly because there may be great information available online. Use search terms like “my state (CA, ME, IL, etc.) water well logs”, “my state groundwater quality”, or “my state well water quality”.
Contact us directly – If these other local sources don’t work out for you, we may be able to help. We may be able to provide direct assistance, and/or direct you to a technical assistance provider in your area who can help answer your questions. (This is a free service funded by the US EPA).
Additional Resources
Home Water Treatment. Minnesota Department of Health.
Want to learn more about your private well and how to care for it?
Sign up for the free 10-week email course from PrivateWellClass.org. The class is a project of RCAP and the University of Illinois, with funding from USEPA.
Not finding the answer you need?
Send us a message in the chat or call us at 1-866-945-0699.