Manganese causes interesting issues for pool owners and is often difficult to diagnose. If your pool water turns purple or black after the addition of chlorine, this can indicate a manganese problem. As the manganese is oxidized by the chlorine or non-chlorine shock, the water darkens. You could have crystal clear water one second and the next- black water! This can cause alarm for pool owners. No need to worry, with the proper diagnosis and treatment the problem can be addressed and rectified.
How To Treat Manganese Staining
Superchlorination is the best way to treat manganese staining. The superchlorination oxidizes the manganese completely and allows it to settle to the bottom of the pool. It can then be vacuumed out. The “rust”-like substance that settles on the pool floor should be vacuumed out. You then need to clean your pool filter. The manganese has the tendency to stick.
If You Don’t Treat the Stain
If you do not treat the manganese staining it can result in unsightly stains on the pool surfaces, especially on plaster, pebble-tec, marcite, and tile grouting. The stains usually appear purple or black, making them very noticable.
How Does Manganese Enter My Pool?
The EPA limits manganese in water mains, it should not be a problem if the water is used in a swimming pool. Manganese can cause problems in swimming pools near to processing plants containing higher levels of the substance. It can also come from pools that are fed from wells which have traces of the mineral.