Tannin is a natural forming underground organic substance that is found in water wells. It is derived from dissolved and decayed organic matter in the water. Coal seams in Alberta water wells are a common cause of tannin. Water with tannin will be brownish in colour, taste bitter, stain laundry and sinks, toilets, and tubs, as well as causing corrosion on chrome plumbing fixtures. The most effective way to remove tannin from water is to use Nano or Ultra Filtration Systems. An initial water test needs to be done to determine what pre-treatment is necessary. Tannin removal systems can be expensive but are incredibly effective. Whole house Nano-Ultra filtration systems are the same as a whole house RO system except for they have a different type of membrane in them.