With more than 30 years’ experience in the residential and commercial water treatment space, Mark Nelson is a Class 1 Drinking-Water Operator and a CBWA (Canadian Bottled Water Association) Certified Plant Operator. As founder and president of Nelson Water in Ottawa, Mark focuses on dealing with challenging water treatment system designs for problem water. He also heads the largest water bottling plant in the city of Ottawa with a delivery network throughout the Valley.

If your drinking water is supplied by a well and you don’t have a water filtration system, it’s likely that you encounter contamination issues on a regular basis. This could range from high concentrations of iron, strong sulfuric odors, hard water, and tannins. If you’re not familiar with tannins, you may be surprised to learn that they are found in compounds that impart that bitter taste that you find in unripe fruit, dark chocolate, and wine. So, what are tannins doing in your well water? Are they harmful? And how do you get rid of them for good? Let’s find out.

Are Tannins a Contaminant?

Yes, at least when they are found in a supply of water, they are considered to be a contaminant. When tannins are found in water, they turn the water a brown, yellow, or amber color that is often mistaken for dirt or sediment. If you spend a great deal of time outdoors, you may see water contaminated with tannins. This is a common phenomenon in many rivers or lakes, and if the water source for your home is in a coastal or swampy area, tannins can enter your tap water.

What are Tannins?

Tannins are organic plant materials, and they appear naturally in water. The most common theories are that tannins are produced as a byproduct of fermentation when water passes through an area with swamp soil or vegetation that’s decaying. The best example that we can present is a simple teabag, it contains dried vegetation (the tea), and when hot water passes through it, the tannin molecules are dissolved. This changes the taste of the water into tea, and it changes the color in accordance with the type of tea you are making. Now try to image some water passing through some decaying vegetation or peaty soil and then flowing into a stream, river, lake, or aquifer, and you can see the same principle at work. The tannins are absorbed into the water, causing discoloration and a bitter or stringent taste.

How Do Tannins Enter My Water Supply?

If your home is supplied by a well, it’s easy to see how tannins could enter your water. After all, the water may pass through vegetation as shown above, or organic materials could enter the well and add tannins there. This compound can easily leach into your groundwater sources that feed your well and enter a private well through cracks in the well wall.

But, how can this happen if your water is supplied from a municipal water treatment plant? If you live in an area where the public water is sourced from another area near the coast or a swampy location, you can still find tannins in your drinking water. The water treatment plant does not remove tannins, and they are not considered to be a major threat to health.

Do Tannins Represent a Health Hazard?

Although tannins are a contaminant in water, they are considered to be more a nuisance and not a serious health hazard. In fact, most of the issues that homeowners are affected by are aesthetic in nature. This manifests as a bitter taste and unpleasant color in drinking water that makes it unpalatable. Let’s take a look at seven problems that are associated with tanning contamination in water.

  1. Tannin Stains: Tannins can cause dark brown or light yellow colors in the water. This is a tea like tint that can cause staining. If you have tannins in your water, you may notice permanent staining of china, fabrics, laundry, and plumbing fixtures in your home.
  2. Bacteria Growth: Tannins can accelerate the growth of bacteria in water.
  3. Water Clarity: Because tannins can affect the water clarity, they can be oxidized easily, and this will have an impact on certain disinfection methods, including chlorination and UV light.
  4. Iron Removal: If you have elevated concentrations of iron in your water, the presence of tannins can make iron harder to remove.
  5. Mineral Binding: Tannins can bind with the mineral content in water; this softens the water and lowers the pH level. This may seem like an advantage because the water will be softer, but it will be more acidic. Bear in mind, if you use this water to fill an aquarium, the acidity will cause stress for the fish. Under these conditions, aquatic life is unlikely to thrive.
  6. Chlorine Byproducts: Tannins can react with chlorine, and new compounds are formed. These are known as disinfection byproducts, and the most common is trichloromethane, which is suspected to be a carcinogen.
  7. Water Treatment: If you have other water filtration systems installed, they can be affected by tannins. The tannins coat the surface of iron, neutralizing and cation exchange filters, reducing their efficacy and efficiency.

How Would I Know if There are Tannins in My Water?

Relying on your sense is not accurate when it comes to detecting water. If you only have trace amounts, it can be hard to notice with a water test. A good water test will also detect other types of contaminants, including bacteria, trihalomethanes (THMs), total dissolved solids (TDS), volatile organic compounds (VOCs), inorganic chemicals, heavy metals, and more.

The Importance of Well Water Testing

If your home is supplied with well water, it needs to be tested regularly. This is crucial because you need to secure a safe and reliable source of drinking water for your home. There are five main reasons why you need to check your well water annually; they are:

  1. Information: Regular well water testing will help you to learn more about the quality of your water and any contamination issues.
  2. Protection: When you’re informed about your well water, you can take steps to protect it against potential contamination.
  3. Tracking: Annual well water testing helps you to understand how the quality changes over time.
  4. Feedback: Regular testing will help you to determine the efficacy of your water treatment systems.
  5. Confidence: When you’re informed, you will have confidence that your water is safe to drink and use in the home.

If you want to get your well water tested or remove tannins, contact your local water treatment specialist today.