Iron in concentrations as low as .3 parts per million can cause staining. Iron can also clog pipes and damage the internal parts of water-using appliances. The elemental form of iron is found in the ground. Ferrous iron is in a dissolved state within a water supply and will not cause any discoloration, although a distinct metallic taste will be present. When the dissolved iron reacts with oxygen however, ferric iron results.
Ferric iron turns the water a hazy, reddish-brown color and makes it very unappealing.
Ferric iron stains bathtubs, sinks and fixtures when it comes in contact with them. Even though iron is generally dissolved in water, when the water is drawn from the tap, the iron reacts with the oxygen in the air and enters the ferric state. In some cases, water may already carry ferric iron when it's drawn from a faucet, and may appear discolored. No matter which form iron appears in, there is a solution available. When iron appears in excessive amounts, a specialized iron removal system may be required.