Tannins in well water: tea-colored water and how to clear it
Short answer
Tannins are natural organic matter from decaying leaves and peat. They give water a yellow or tea color that doesn't settle out the way iron does. They're harmless to health but stain laundry and fixtures. The usual fix is a tannin filter using anion exchange resin. UV systems need tannins under 0.1 ppm, so treat them before UV.
Tannins or iron?
Fill a clear glass and let it sit for a few hours. If color settles to the bottom, it's likely iron. If the water stays evenly yellow, it's likely tannins. A lab can measure both.
Treatment
- Anion exchange tannin filter, regenerated with salt like a softener
- Combination softener/tannin units for water that is both hard and tannic
- Activated carbon for very light tannins (it fills up fast)
Put iron removal before the tannin filter. Iron fouls tannin resin.
Questions well owners ask
Are tannins in well water dangerous?
No. They're an aesthetic problem: color, taste and staining.