Iron Removal for Water Softeners

Iron in your home water supply is not a health hazard, but it stains clothing, appliances and fixtures an ugly, brown color. Ion-exchange water softeners can remove small quantities of iron, but may get clogged with higher iron concentrations. Other types of water treatment remove iron and some other impurities by oxidizing the iron and filtering it out, helping avoid water softener damage. You have to get the right type of water treatment for your iron problem.

Woman drinking glass of water in kitchen, view through window
credit: Michael Blann/Photodisc/Getty Images
Water containing iron may look clear, but still leaves stains.

Types of Iron

You can have two types of iron in your water supply, and water softeners only work for one of them. Ferrous iron is soluble in water, and the water remains clear, but as the water is exposed to air, the ferrous iron changes to ferric iron. Ferric iron is like rust, and forms small brown flakes in the water or colors it a brown color. If ferric iron combines with organic material or reacts with bacteria, it forms a sludge or gelatinous material that clogs your water softener and releases slugs of brown jelly into the water supply.


Traditional ion-exchange water softeners that work with salt regeneration can remove ferrous iron in the same way they treat water hardness. If your water reaches the water softener without being exposed to air, this method is effective. If your water is exposed to air -- for example, in a well -- the ferrous iron changes to ferric iron. The water softener still removes small quantities, and the regeneration process cleans out the iron, but for larger amounts of iron, the ferric iron fouls the ion exchanger, reducing its function. Iron that has formed a sludge clogs the water softener and has to be treated separately.


For water supplies that have a high iron content, it helps to introduce oxygenation before the water softener to create rust particles that can be filtered out. Such systems introduce oxygen into the water with oxygen-containing chemicals such as chlorine, or via aeration, then filter the water before releasing it for treatment in the water softener. This method avoids water softener fouling, and can handle high levels of ferrous iron, but the oxygenation does not affect iron that has reacted with organic material or bacteria.


For water softeners being fouled by slime resulting from organic or bacterial iron, a robust filter may solve the problem. A sand filter with a frequent and powerful backwash action can remove iron sludge from the water and prevent it from accumulating in the water softener. These filters operate similarly to swimming pool filters, and need a drain pipe to remove the backwash water. The sand may have to be replaced periodically, depending on the amount of filtering the water requires.

Bert Markgraf

Bert Markgraf

Bert Markgraf is a freelance writer with a strong science and engineering background. He started writing technical papers while working as an engineer in the 1980s. More recently, after starting his own business in IT, he helped organize an online community for which he wrote and edited articles as managing editor, business and economics. He holds a Bachelor of Science degree from McGill University.