Tannins in Water: What Are They & Where Do They Come From?

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If your well water has a yellowish, tea-like color and a musty smell, you might be concerned that it’s contaminated with something nasty.

Most likely, the source of contamination is tannins. While tannins aren’t dangerous in drinking water, they can give water an unpleasant taste and smell.

In this guide, we’ve shared everything you need to know about drinking water tannins, including what they are, where they come from, and how to test for them.

๐Ÿ“Œ Key Takeaways:

  • Tannins occur in drinking water when this water passes through decaying vegetation and organic matter in the earth.
  • Coastal areas, shallow wells, and surface water sources are most prone to tannins contamination.
  • You can test for tannins with a DIY at-home test kit or a laboratory test.

๐Ÿค” What Are Tannins In Water?

Tannins are yellowish coloration that occurs in water that passes through peaty soil and natural organic matter in the earth.

Alongside iron, manganese, and hardness minerals, tannins are common in well water that doesn’t undergo pre-treatment before it’s delivered to a home.

Tannins are present in surface water supplies (such as rivers and lakes) as well as groundwater supplies (like underground aquifers). Shallow wells, marshy areas, and low-lying or coastal areas are most likely to experience tannins contamination.

Tannins in water

๐Ÿ”Ž How Do Tannins Get Into Water?

Tannins get into drinking water as this water passes through decaying vegetation, peaty soil, and other natural organic materials in the earth.

As water travels through layers of soil and earth into a well aquifer, some of the color from the organic matter and decaying vegetation in the earth leaches into the water. This causes the water to take on a yellowish color.

The easiest way to imagine tannin contamination is to think of making a mug of tea. When you pour water over a teabag, tannins from the tea cause the water to change color.

๐Ÿ“ Signs Of Tannins In Water

So, how do you know if you have tannins in your drinking water supply?

There are a few signs to look out for:

  • Water with a yellow or brown tea-like color
  • A musty odor or earthy odor
  • A bitter taste
  • Yellow staining of your laundry, toilet bowl, and white dishware

You might also find that certain foods taste bitter if you cook them in water containing tannins.

Tannins often get confused with iron and manganese, which are also common in tap water from a well. We’ve discussed how to know which contaminant your water contains later in this guide.

Yellow, tea-like color from tap water in home

๐Ÿง Are Tannins Harmful In Water?

Are tannins in water harmful to humans?

No, from a health perspective, drinking water tannins aren’t harmful. That means it’s safe to drink water containing tannins without the concern that you might get sick or develop health problems.

However, tannins can be aesthetically harmful in your home, meaning that they’re known to stain surfaces.

Tannin-contaminated water in your washing machine may stain your clothes light yellow, and particularly high concentrations of tannins may even cause your white dinnerware and porcelain fixtures to be stained.

๐Ÿšฐ Are Tannins Regulated In Drinking Water?

No, tannins aren’t regulated in drinking water. However, they do have a secondary drinking water standard (which isn’t legally enforced) for coloration.

Why do tannins have a secondary drinking water standard, and not a primary regulation? Essentially, tannins are considered a nuisance contaminant with aesthetic effects, but they aren’t a health hazard.

The Environmental Protection Agency (EPA) only regulates contaminants that have health effects. Since tannins don’t fall into this category, they’re not regulated. However, many municipal suppliers and private well owners reduce tannins in their water for aesthetic purposes.

๐Ÿ†š Tannins Vs Iron In Water

Tannins and ferric iron have similar properties in water: both give water an orange tinge and both stain surfaces.

The best way to find out whether your water has tannins, iron, or both, is to conduct a water test (more on that below).

But if you’re looking for a free and faster method of detecting either one of these contaminants, here’s what to do:

  1. Fill a glass with water from your faucet.
  2. Let the glass sit overnight.
  3. Observe the intensity of color.

If the orange coloration is darker at the bottom of the glass, you likely have iron or manganese (or both) in your water.

If the orange coloration is still consistent throughout the water in the glass, you probably have tannins.

Or, if you notice some settling at the bottom of the tank but your water still has a yellow or brown tint, you might have tannins and iron.

Tannin vs iron water testing

๐Ÿงช How To Test For Tannins In Water

To learn whether or not your well water supply contains tannins, and what concentration of tannins are present, buy a tannins water test.

DIY At Home Tannins Test

You can buy a simple tannins test kit online (costing $30-$60 on average) that lets you test for tannins at home.

To use the test, you add a couple of drops of liquid reagent (included in the test package) to a small sample of your water.

You then add a titrant solution to the water sample one drop at a time, counting each drop, until the liquid stays consistently pink/red for 1 minute.

You can work out the concentration of tannins in your water based on the number of drops you used to turn the water pink or red.

Laboratory Testing

If this all sounds like too much work for you, you can save yourself the effort (but spend more money) with a laboratory water tannins test.

There are dedicated laboratory tests for tannins (we recommend this test sold by Tap Score), which cost around $50-$80. You can also buy testing packages that test for a handful of common well water contaminants, including tannins, which costs around $80-$150.

If you buy a laboratory test for tannins, you’ll just need to send off a sample of your well water to the lab. You’ll then receive your test results within 2 weeks.

The benefit of laboratory testing for tannins is that it provides clearer, more accurate results – but it’s also about 2-3 times the price of a DIY tannins test.

Getting tap water tested with tapscore

๐Ÿ“‘ Final Word: Dealing With Tannins In Water

Once you’ve tested and confirmed that your water contains tannins, it’s up to you whether or not you want to remove them with a tannin filtration system.

As we mentioned, tannins aren’t dangerous in your water, despite their bitter taste and unpleasant color.

But you might want to remove them and improve your overall water quality. If so, you’ll be interested to read our guide on the best methods to remove tannins from well water.

  • Jennifer Byrd
    Water Treatment Specialist

    For 20+ years, Jennifer has championed clean water. From navigating operations to leading sales, she's tackled diverse industry challenges. Now, at Redbird Water, she crafts personalized solutions for homes, businesses, and factories. A past Chamber President and industry advocate, Jennifer leverages her expertise in cutting-edge filtration and custom design to transform water concerns into crystal-clear solutions.

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