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Tannin Water Treatment

Discoloration Due to Tannin

Tannins are dissolved, decayed organic matter in the water, and generally not a health risk. Tannins appear primarily in river or surface water and swamps (Florida), but, often find their way into wells through cracks and fissures in rock formations.

Tannins will generally cause a yellow, yellow/brownish tinge to the water. They come from decayed vegetation or animal matter and are carbon-based. This is significant because carbon tends to deplete oxygen and tannin-laden waters will reduce the amount of free oxygen in water. This depletion of oxygen helps explain how tannins contribute to the problem of acid water.

Tannins also prevent iron from being oxidized and precipitated (process whereby iron is changed from a dissolved form to a particle). Tannins in water are responsible for many failures of iron removal filter systems and water softeners. The best way to remove the iron in cases such as this is to treat the iron as an organic and remove it with a tannin filter media.

There are so many variations of tannins that they are hard to define and measure with standard testing. We have heard of estimates of 12,000 different types of tannins. Some companies offer Lignin Test Kits or more advanced labs have a T.O.C. (Total Organic Carbon) test, but, neither test is foolproof.

Tannin Concentration in
Parts Per Million (PPM)
Water color
0 - 0.5
Faint tinge of yellow
0.5 - 2.0
Darker golden yellow (ginger ale)
2.0 - 3.0
Light tea color
3.0 - 5.0
Dark tea color