How to Remove Tannins From Water

Reviewed by: James Layton
Updated on:
January 17, 2024

Key Takeaways

How to Remove Tannins From Water

Life in the modern world has its advantages, including multiple advanced water filtration technologies.

Finding the right filtration method to remove tannins from your water involves testing your water to see what else is present. That way you can tackle multiple impurities with as few filtration systems as possible.

Reverse osmosis systems (RO)

Reverse osmosis systems can effectively remove large-molecular-weight tannins in water.

RO systems can tackle many other contaminants, such as microbes, volatile organic compounds, metals, and hydrogen sulfide. If you have a wide variety of toxins besides tannins, RO is your best bet.

Reverse osmosis systems are most common at the point of use, such as the kitchen sink. They are available for the whole house, as well, though, which may be the solution if you’re dealing with high tannins.

Check out our review of the best whole-house reverse osmosis systems for more information.

Anion exchange systems

Anion exchange resin replaces negatively charged tannin ions in the water with chloride ions.

Besides tannins, anion exchange systems, which are designed for the whole-house, and their specific resins can also remove nitrate, fluoride, and arsenic.

The system backwashes and regenerates itself using brine water every two days. Typically, it will require two to three bags of chloride every month and about 50–80 gallons of regenerating water in every cycle.

One downside of anion resins is that toward the end of the life of the resin, it starts giving off an unpleasant fish odor in the anion resin bed. The foul smell becomes more prominent if the water is hard.

Regular regeneration can diminish the smell, but if water pH levels are greater than 8, the problem will resurface frequently.

It’s best to pair up an anion exchange system with a water softener that removes hardness-causing minerals that can otherwise damage the anion bed. Although a water softener doesn’t directly remove tannins, it improves tannin absorption in the anion exchange filter.

A good quality whole-house anion exchange system can cost anywhere from $800 to $3,000.

Activated carbon filters

Activated carbon filters can remove tannins and other organic contamination. However, they are not as effective as the anion-exchange method. They are cheaper though.

This system can be combined with a reverse osmosis system for optimal results.

For better results, you can also go for an arrangement in which tannins are oxidized first using chlorine in a retention tank.

Chlorine injection

Chlorine can effectively break down tannins to later be adsorbed by a carbon filter.

However, in cases of high tannins, this method can produce trihalomethane, a carcinogen made by a combination of chlorine and tannins. Luckily, activated carbon can remove it.

In fact, while tannins aren’t often found in municipal water, the reason they’re not found in municipal water is routine chlorination. The tannins react with the chlorine, resulting in trihalomethane in city water supplies.

Interestingly, chloramine, or a combination of chlorine and ammonia, does not react in the same way with tannins so does not result in trihalomethane. If you’re on city water and you’ve heard of chloramine, remember that it’s not all bad.

But I digress.

Shock chlorination coupled with carbon filters is an affordable route if you don’t want to spend heaps of money on removing tannins.

However, if tannins are an ongoing problem, a more permanent solution than chlorination may be in order.

Ultrafiltration (UF) membranes

Ultrafiltration membranes use hydrostatic energy to force water through the filters. As a result, heavy molecular particles are trapped in the system while low-molecular-weight solute passes through the filter.

A semipermeable membrane captures many types of suspended contaminants in water, like natural organic material, bacteria and viruses, and other dissolved solids.

These filters are available in different pores sizes ranging from 0.005 to 0.1 micron.

UF membranes need regular maintenance to flush away the captured particles in membranes lest they get clogged.

For UF to work efficiently, you need to pretreat the water for any iron and hardness-causing molecules.

To be honest, they’re more practical in industrial application than residential.

What Are Tannins?

Tannins — containing fulvic and humic acid — are a group of organic molecules that make plants, trees, leaves, and fruits unpalatable to insects and other predators.

These astringent molecules, such as witch hazel, play a big role in protecting vegetation and regulating plant growth. Have you ever noticed a mouth-coating, puckery, or dry sensation in your mouth after eating an unripe fruit?

Tannin molecules cause that.

How Do Tannins Enter Water?

Tannins are generally more common in marshy, low-lying areas along the coast or near a body of water. When leaves, tree bark, and other types of vegetation decay, highly soluble tannin molecules are released into the soil and slowly find their way into the aquifer.

Sometimes, surface water, or local runoff, passes through the decayed leaves and tannin-rich soil and absorbs all the tannins before seeping into your well through cracked well walls.

Effects of Tannins on Drinking Water

Water extremely contaminated by tannins will appear yellow or brown, like tea or apple juice, depending on the concentration of contamination.

Did you know that the Blackwater River of Florida is black because of the presence of tannins? Well, now you do.

In addition to a darker appearance, tannins also affect taste and odor. The astringent in tannins adds a bitter taste and a musty, plant-like smell to drinking water.

Despite the physical effects, which may be alarming to the observer, tannin water is not toxic. Tannins are organic plant molecules that are harmless to humans. Many beverages and foods that we consume daily contain tannins, including coffee, leafy vegetables, and legumes.

What is problematic is the strong staining ability of tannins. If you wash your laundry and utensils with this water, you’ll end up dyeing all your clothes and linens, not to mention your white porcelain basins and ceramic floor tiles.

How to Test for Tannins in Well Water

It’s not a good idea to rely on appearance alone to diagnose a tannin problem. And there are no DIY testing kits that will test for tannins. You can buy a tannin test on the internet for about $300, but it doesn’t test for anything else.

That’s a lot of money to spend on something you’ll use once.

I’ve got a better idea.

Send a sample to a lab.

It’s often hard to distinguish tannins from ferrous and ferric oxide at home.

The best way to check for tannins in your water is to send a sample or send your tap water to an accredited laboratory. Laboratories use special methods to accurately determine the concentration of each type of contaminant in your water.

The results will help you get a good idea of what is lurking in your water.

You can either test only for tannins only or go for a package that covers ferrous, ferric oxide, manganese, total dissolved solids, volatile organic compounds, sulfur, and more to get a wholistic overview.

Final Thoughts

Before moving into a new home, make sure you test the water quality and observe the structure and location of the well, if there is one.

Tannins in water are not harmful to consume, but they give the water a musty odor, bitter taste, and tea-like color that can stain your white fixtures and laundry.

There are a few water filter systems to help remove tannins, such as ultrafiltration membranes, anion exchange system, chlorination followed by active carbon filtration, and reverse osmosis.

Choose the one that suits your needs, and if you’re indecisive, don’t hesitate to seek expert advice. 

Interested in delving deeper into various water treatments? Expand your knowledge using these additional resources:

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In a 5 stage RO unit, which filter tends to clog up and slow the flow first? Wondering if changing only the sediment filter (easier and cheaper) extends the cycle for the more expensive filters (tannin filter is pricey).

James Layton

Hello Dennis, This is a very good question. I can say with 100% confidence that the first filter in the series of filters will be the first cartridge to get clogged. This is normally a sediment filter. It will capture suspended particles but the other thing that happens is it gets coated with naturally occurring bacteria. Even with chlorinated tap water, eventually the inside of the filter canister and the sediment filter will get slimy from bacteria. This is normal and happens with just about all home water filters.The cartridge will have a reduced flow rate due to these factors. I change my sediment filter every 6 months. When I was using a spin-off filter housing I could feel the slime inside the housing. I would soak the canister with water containing about a teaspoon of bleach. After an hour I would scrub out the canister with a bottle brush. You can use dish detergent after bleaching. I am now experimenting with a counter-top RO system. The cartridges are sealed, meaning you simply twist off the filter and replace it with a new filter. You’ll never be able to notice the slime build-up. That is why I change it every 6 months. It really helps keep the flow rate up.