Tannins are naturally-occurring particles in plants, flowers, trees and other organic materials. They play an integral role in the flavoring and coloring of wine, and herbs containing tannins have been used in the process of tanning hides for centuries. Tannin coloring can cause trouble in swimming pools. When leaves, branches and other organic materials fall into the water and settle on the stairs, walls or floor of the pool, they can leave black or rust-colored stains. Tannin stains will dissolve under an intensive chlorine treatment.
Things You'll Need
Pump or bottom vacuum
Water chlorine test
Chlorine shock treatment
Increase the water circulation in your pool. Depending on the type of pool you have, you may be able to simply turn the pump up higher. Using a bottom-cleaning vacuum can also increase water circulation, which will increase the stain's exposure to the chlorine in the pool.
Measure the level of free chlorine in your pool, using a chemical test kit. Follow the instructions to ensure that you read the free chlorine level. Free chlorine fights off bacteria in your pool. A pool generally contains two to four parts per million parts of water.
Add a super-dose of chlorine as a shock treatment. The extra chlorine must bring your free chlorine reading up to at least six PPM for an effective shock treatment. Use your regular chlorine product or special shock treatments.
Add the recommended chlorine to maintain a reading of at least six PPM for two days, or until you see the tannin stain dissolve completely. Once the stains are gone, stop adding the extra chlorine. Your water should return to its normal PPM reading within two days.
If you apply Vitamin C tablets to the stain and it begins to dissolve, you have metal stains. Those require different forms of treatment.
Read all product instructions and warnings for chlorine products and shock treatments to avoid ruining the pool water or making the pool unsafe for swimmers.