Does Reverse Osmosis Remove Iron from (Well) Water?

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Well water is prone to various contaminants, and while some are just aesthetic issues, others can cause more serious problems.

Iron is one of the latter; it can lead to discolored laundry and clogs in your appliances among other issues.

If you’ve got a well with iron present, you may wonder if your reverse osmosis system can help eliminate it.

In this article, we’ll discuss whether reverse osmosis can remove iron from well water.

Key Takeaways

  • Reverse osmosis is capable of removing all types of iron from water.
  • Higher concentrations of iron may require specialized iron filters for removal.

Ferrous, Ferric & Organic – Does Reverse Osmosis Remove Iron from Water?

Reverse osmosis can remove any type of iron, whether it is in a ferrous (dissolved) or ferric (insoluble) form. It can also remove organic-iron-containing compounds such as chelated iron.

However, if the water contains high levels of iron, it may require a specialized iron filter for removal. Too much iron increases the chances of your RO unit clogging, so a pre-filter may be necessary.

Generally speaking, it is not recommended that you run anything more than 0.3 ppm of iron through a reverse osmosis system.

How an RO System Removes Iron

A standard RO system consists of three main filtration stages, all of which have a hand in removing iron from water. Each stage is discussed in detail below.

Sediment Pre-Filter

The first stage of an RO system is a sediment pre-filter. This mechanical filter is designed to remove sediment and other large particulates, including ferric or insoluble iron. It works like a screen door, trapping the large particles inside a filter media and allowing clean water to pass through.

Carbon Filter

Carbon filters are the next stage of an RO system. This filter uses activated carbon to remove ferric iron and other contaminants such as chlorine and VOCs.

Just like a sediment filter, the carbon filter media acts like a sieve, blocking larger bits of floating iron as the water passes through.

Different Water Filter Cartridges and Membranes

Semipermeable Reverse Osmosis Membrane

The final stage of an RO system is the semipermeable membrane. This is where all types of iron and other contaminants, such as lead and fluoride, are removed from your water.

The tiny openings in this membrane allow almost only clean water to pass through while trapping the impurities on the other side.

Reverse osmosis membranes remove ferrous, ferric, and organic forms of iron.

What Are Other Iron-Removing (Well) Water Treatment Systems?

You have a few options if you want a specialized iron treatment system to go together with your RO unit.

For Ferrous (Clear-Water) Iron: Water Softeners and Iron Filters

Ferrous iron is iron that is dissolved in water. Therefore, you won’t be able to see it unless the water is tested.

There are specialized iron filters, such as greensand, Pro-OX, or Birm filters, that can be used to reduce clear-water iron in wells. These systems rely on oxidation and filtration. They typically require periodic backwashing to prevent clogging from the iron.

While not classified as a filter, a water softener can also remove ferrous iron. This is because it exchanges mineral ions with sodium or potassium ions from a special resin bed inside the tank.

That said, water softeners are mainly used to remove hard minerals like calcium and magnesium

For Ferric (Red-Water) Iron: Iron and Mechanical Water Filters

Ferric iron is insoluble and does not dissolve in water. It appears reddish-brown, which is why it’s sometimes referred to as red-water iron.

Mechanical and specialty iron filters can remove ferric iron from water.

  • Mechanical filters (like sediment and carbon filters) use a physical barrier to trap particles as small as a few microns in size.
  • Iron filters typically contain media such as greensand or Birm, which oxidizes the iron and traps it inside the filter bed.

For Organic Iron and Iron Bacteria: Chemical Oxidation + Filtration

Organic iron is bound to organic compounds such as humic acid. It’s typically found in water with high levels of dissolved organic matter and can be difficult to remove without chemical treatment.

On the other hand, bacterial iron is caused by the presence of iron-oxidizing bacteria. These bacteria can produce a slimy substance that accumulates in your plumbing lines, leading to clogs and other plumbing issues.

Chemical pre-oxidation is typically used for both organic iron and bacterial iron removal. Chlorination is a popular choice for this purpose; it oxidizes the compounds so that they can be filtered out with an appropriate mechanical filter.

How to Detect Iron in Water

There are several indicators of iron in well water, but it’s best to get a professional test done to determine the exact level. Here are a few signs there may be iron present in your well water:

Metallic Taste

Iron can give your water a metallic taste, similar to the taste of pennies. If you detect this in tap water, it may be time to test for iron.


Iron can cause clogs in your appliances, such as dishwashers and washing machines. This is because the iron combines with other minerals in the water to form a sticky residue that can build up over time.

Staining or Discoloration

Iron in your water can cause staining of sinks, tubs, toilets, and clothing. If you notice any discoloration around these areas or on clothing washed with the water, it could be a sign of iron in your well.

Conducting a Water Test

To reliably determine whether there is iron in your well water, you’ll need to get a professional test done. The test will measure the total amount of iron in your water, its pH level, and other factors that could be causing staining or other problems.

Once you have this information, you can easily decide what type of filtration system best suits your needs.

Water Testing Report

What Is Iron and How Does It Get into Our Water Supplies?

Iron is a mineral that occurs naturally in the earth’s crust. It can make its way into our water supplies from natural sources, such as when it leaches from soil and rocks. Iron can also come from manufactured sources, such as corroding pipes or agricultural runoff.

Regardless of the source, iron can be present in both well and municipal water supplies. However, the former is more likely to contain higher concentrations.

The Negative Effects of Iron in Water

Iron can cause issues in parts of your home but is not usually a health hazard. In fact, the human body needs iron to function properly since it is a crucial component of hemoglobin in the blood.

However, high levels of iron consumption can damage vital organs like the heart, liver, pancreas, and spleen. The World Health Organization (WHO) reports that the average lethal dose of iron is 200–250 mg/kg of body weight, which leads to hemorrhagic necrosis and sloughing of areas of the mucosa in the stomach. But iron overdoses are rare, especially amongst generally healthy people.

What’s a Safe Level of Iron in Drinking Water?

The Environmental Protection Agency (EPA) has issued secondary drinking water standards that set the maximum acceptable concentration of contaminants in drinking water. For iron, the standard is 0.3 ppm.

If you have any thoughts about the question, does reverse osmosis remove iron from water, please don’t hesitate to leave a comment below!

About the Author Gene Fitzgerald

Gene Fitzgerald is one of the founders of BOS and currently head of content creation. She has 8+ years of experience as a water treatment specialist under her belt making her our senior scientist. Outside of BOS, Gene loves reading books on philosophy & social issues, making music, and hiking.
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