Iron and Manganese
Iron and manganese are naturally occurring metals which are of concern as they can cause discoloration and off flavors in water and staining of laundry and plumbing fixtures. Chlorine bleach may react with these metals and intensify staining of laundry.
Iron and manganese can effect the flavor and color of food and water. Manganese is objectionable in water even when present in small concentrations.
Except in rare cases, iron is not considered hazardous to health. Iron levels greater than 0.3 mg/L and manganese levels greater than 0.05 mg/L are considered likely to cause red, brown, or yellow staining of laundry, glassware, dishes, and household bathtubs and sinks.
When iron and manganese exist along with bacteria, a brownish-black (manganese) or reddish-brown or yellow (iron) slime can develop that can clog plumbing and cause an offensive odor. This slime or sludge may be noticeable in your toilet tank when you remove the lid.
Low levels can be removed with a water softener or with reverse-osmosis filtration, while high levels may require an iron removal system.