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Tannins & Groundwater
What are the health effects of Tannins?
Tannins are considered an aesthetic problem. While they may make water unappealing to
drink and stain laundry, they generally present no health hazard. It should be noted that tannins can sometimes interfere with equipment used to treat other water problems. For example, the resins or medias in iron filters, cation exchange filters and neutralizing filters can become coated by the tannins, and may no longer work properly.
Should I test my water for Tannins?
Tannins create a light yellow to dark brown discoloration in the water. A simple test for
tannins involves filling a clear glass with water and letting it sit overnight. If the colour settles to
the bottom of the glass, the discoloration is most likely caused by iron and/or manganese and
not tannins. If the intensity of the colour remains intact, it is most likely caused by tannins.
If you suspect your water may contain tannins and wish to know how much tannin is present in
your water, contact an Accredited Water Testing Laboratory that can perform tannin testing.
You may also wish to test for sulphates, alkalinity, iron, total dissolved solids (TDS) and hardness,
as these may help determine which treatment method(s) will be most effective for your
situation. There is another reason to test for iron along with tannins; iron creates a false
positive for tannins and must be subtracted from the tannin result to determine that true
What can I use to remove Tannins from my water?
Treating by oxidation and filtration is one method to remove tannins. Another treatment method includes using an anion exchange resin. The anion resin is sensitive to hardness, so most systems include a water softener as a pre-treatment.
We are happy to refer water treatment specialists in your area for assistance.