What Are Tannins in Water?

July 22, 2022
This guide will look at tannins in detail

If your water is murky or has an yellow tinge, it may contain tannins. This guide will look at tannins in detail, including how tannins get into water, their effects in a water supply, how to test for tannins in water, and how to remove them. 

What Are Tannins?

Tannins are naturally occurring fermented materials that are produced by the breakdown of vegetation and are found in soils, tree barks, leaves, and other plant structures. These materials aren’t harmful to human health, but affect the color, taste, and quality of drinking water. 

How do Tannins Enter A Water Supply?

Most tannins enter water through soil seepage: when water seeps through layers of soil and decaying matter. 

Surface runoff can also deliver tannins into a water supply. Low-lying, marshy, or coastal areas, or areas that contain a lot of decaying vegetation, are more susceptible to water tannin contamination. If a lake or river supplying drinking water contains tannins, the drinking water will likely contain tannins, too.

Tannins may be reduced in public drinking water to improve its appearance and taste. People who get their water from a private source, like a well, will need to remove the tannins themselves. 

Signs of Tannins in Water

Some of the common signs of tannins in water are: 

  • A yellow, tea-like water color
  • Yellow staining on laundry, fixtures, and china
  • A musty or earthy odor
  • Bitter, unpleasant aftertaste

Effects of Tannins in A Water Supply

If your water contains tannins, you may notice the following effects in your water supply: 

Stained Fixtures

Sinks and toilet bowls will develop yellow staining if they’re in regular contact with water containing tannins. This staining is difficult to remove and may not come off with standard bathroom cleaning products. 

Stained Laundry

Washing your clothes with water containing tannins may leave stains on your fabrics. Light-colored laundry is especially susceptible to tannin staining. 

Unappealing Drinking Water

Tannins give water an unappealing appearance, taste and smell. Some people think that tannins have a musty, earthy taste. Tannin water is also known to be bitter. You may not want to drink your water due to its unpleasant taste and smell.

Are Tannins Dangerous to Drink?

Despite their staining qualities and their effects on water’s taste and smell, tannins aren’t dangerous to drink. The worst that tannins can do is discourage you from drinking water, which could lead to mild dehydration. 

However, if your water contains tannins, there’s a high likelihood that it contains other contaminants - and some of these contaminants could be dangerous to drink. Test your water to find out whether or not it contains harmful impurities. 

How to Test Water for Tannins 

To test your water for tannins, there are two options to consider. 

DIY Test Kit

The first option is to use an at-home DIY test kit. Dedicated tannin tests are the most commonly available DIY tests for tannins. All-in-one tests, which can detect tannins and other common well water parameters, are more difficult to find.

Most DIY kits detect tannin levels between the range of 50 and 300 parts per million (PPM). Follow the instructions to take a sample of water from your faucet and perform the test to get an instant tannins reading. 

Laboratory Test

The second option is to get a laboratory test for tannins. You can choose a dedicated tannins test or opt for a test package that also detects several of the most common well water impurities and paramaters, such as iron, hardness, pH, and bacteria.

Laboratory tests are a hands-off testing option. After taking a sample of your water, send the sample to the laboratory and wait for your results. Most laboratories deliver test results within two weeks.  

Laboratory testing will give a more accurate, detailed reading of tannins in water compared to DIY testing, but lab testing is the most expensive choice.

How to Remove Tannins from Water

The best way to remove tannins from water is with an activated carbon filter. 

Activated carbon is a natural media, usually made from coconut shell or activated charcoal, with a large surface area. When water flows through an activated carbon filter, the media’s pores pull asthetic contaminants out of the water in a process known as adsorption. 

Alongside tannins, activated carbon can also remove chlorine, pesticides, VOCs, and some heavy metals. 

Other tannin removal options to consider are ion exchange tannin softener systems, reverse osmosis water filtration systems, and oxidation systems. 


Tannins are natural materials that aren’t harmful to human health. However, tannins give water an unpleasant tea-like color, musty smell, and bitter taste. 

At-home DIY kits are available to buy online for testing tannins. For more thorough results, consider using a laboratory tannins test. Tannins can be reduced or removed from water with an activated carbon filter, a tannin softener system, or a reverse osmosis system. 

About the Author

Brian Campbell

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