Tannins in Groundwater

Any rural homeowner will tell you the challenges they encounter when using well water. Most city residents get their water supply through government-regulated facilities responsible for the quality and safety of their water. Anyone with a home that uses water supplied by a well is directly responsible for regulating and treating their water. As a homeowner, you may encounter everything from discoloration, strong odors, especially sulfur, and high levels of iron and hardness ion contents as well as tannins in your groundwater.

A responsible well owner will test their water annually for contaminants. You will also need to be keen and pay attention to any local reports of contamination in groundwater. This is especially important for residents near industrial operations or large farms.

One problem that affects well owners is the presence of tannins. This is a significant issue for those with shallow wells or who live in coastal or low-lying areas. This issue that not associated with any particular health or safety concern. However, using water with tannins will lead to unpleasant consequences in your household.

Tannins in Water


Outdoor lovers and explorers sometimes encounter rivers and lakes with amber or light brown water. This phenomenon is common in fast-flowing water. Sometimes, the water will look like root beer as it moves over rocks and descends small waterfalls. Many people mistake the color for pollutants or dirt, but it’s produced by tannins.

When vegetation breaks down, it creates fermented organic materials called tannins. The material dissolves into flowing water as it passes through, and the water acquires a yellow or amber color. For a river to have a root beer color, the water has to flow through marshes, swamps, and other places with high amounts of decayed vegetation. The first flowing water will collect the small plant particles causing the yellow color.

Well water encounters tannins in the same way. Water from the surface will encounter peaty soil and decaying fermented vegetation as it moves down towards the aquifer feeding your well. Like the root beer water in fast-flowing rivers, the water entering your home will acquire a brown or light yellow color. The concentration of the decayed material will determine the color of the water.

How Do Tannins Affect Your Home?

As mentioned previously, tannins do not affect people’s health or safety when consumed. When drunk, the water will have an unappealing color, a musty plant-like odor, and an unpleasant tangy aftertaste. This pigmentation works just like dye and can stain your clothes permanently. You may also find stains that are hard to get rid of on dinnerware and porcelain fixtures.

Tannins in Running Tap Water

How Do You Test For Tannins?

Tannins are not the only cause of water discoloration. High levels of iron will also change the watercolor. If you want to determine whether your water contains tannins, you can use this simple test. Put water in a clear glass and leave it overnight. Examine it in the morning, and if you notice a heavier discoloration at the bottom of the glass, your water likely contains iron. Iron and other heavy particles will naturally settle after some time. If the water retains the same color overnight, then it most likely contains tannins.

Test your water in a certified laboratory if you want more accurate results. Besides tannins, you can also test for several other components that can cause discoloration of your well water, such as iron and other hard minerals.

Tannin Test Kit

Tannin Test Kit

How Do You Treat Tannins?

If you discover tannins in your well water, several options are available for you. However, you need to know that tannins are really difficult to treat despite these options. For example, you cannot use the same treatment method for wells that are a few miles apart because each well has different tannins that come from other plants found in the water.

The process of filtering tannins is unique because it’s not really a true water filter. Instead, it works the same as a water softener. A tannin filter operates by using resin media with ion exchange properties to trap the tannins and other organic particles. Resin beads in a tannin filter are white and very fine. Once the media holding the resin beads reach their capacity, they undergo regeneration. A brine solution washes the medium, and the filtration process is ready to reoccur.

One of the most common tanning treatments is using an organic scavenging anion exchange resin. You will need to install a water softener before using this resin because it is susceptible to hardness minerals. Calcium and magnesium ions reduce tannin absorption and affect the lifespan of the anion resin. Anion resin systems require regular maintenance. You may need to regenerate your system occasionally with a saltwater solution or baking soda, which improves the resin’s effectiveness.

Tannin Filter Valve Front View

A fouled anion resin will cause a fishy odor, and this indicates that your system needs to be cleaned. Before purchasing anion exchange resin systems, you need to know that these systems alter the levels of sulfate, chloride, and alkalinity in your water. Therefore, once you install the system, you will have to monitor how it affects these substances.

Filtration and oxidations remove tannins to an extent through a process that is not as simple as using an anion exchange system or a softening system. You can seek advice from Affordable Water Treatments for a solution custom to your situation.

You need to note that tannins may tamper with water treatment equipment. For example, the tannins may coat the media and resins found in neutralizing filters, iron filters, and cation exchange filters, destroying their functionality. Remember to test for tannins before installing these types of water treatment systems. You can use the simple, clear glass test.

Remember, if your drinking water starts to taste earthy and bitter, or looks like iced tea, get it tested and treated for tannins. Look for an anion exchange or a water filtration system that will remove the tannin problem in your well. Also, don’t forget that the discoloration, odor, and taste issues in your water may result from other minerals commonly found in the well water supply.

Tannin filter Valve side view

Tannin filter Valve side view

For a free estimate call Affordable Water at 204 333-9250