Iron is one of the most troublesome elements in water supplies, and it creates nasty rust in sinks, tubs and toilets. Manganese causes black staining and is often found with iron. Making up at least 5 percent of the earth’s crust, iron is one of the earth’s most plentiful resources. Rainwater as it infiltrates the soil and underlying geologic formations dissolves iron, causing it to seep into aquifers that serve as sources of groundwater for wells. Although present in drinking water, iron is seldom found at concentrations greater than 10 milligrams per liter (mg/l) or 10 parts per million. However, as little as 0.3 mg/l can cause water to turn a reddish brown color.
Iron is mainly present in water in two forms: either the soluble ferrous iron or the insoluble ferric iron. Water containing ferrous iron is clear and colorless because the iron is completely dissolved. When exposed to air in the pressure tank or atmosphere, the water turns cloudy and a reddish brown substance begins to form. This sediment is the oxidized or ferric form of iron that will not dissolve in water.
Iron is not hazardous to health, but it is considered a secondary or aesthetic contaminant.
Taste and Food
Dissolved ferrous iron gives water a disagreeable taste. When the iron combines with tea, coffee and other beverages, it produces an inky, black appearance and a harsh, unacceptable taste. Vegetables cooked in water containing excessive iron turn dark and look unappealing.
Stains and Deposits
Concentrations of iron as low as 0.3 mg/l will leave reddish brown stains on fixtures, tableware and laundry that is very hard to remove. When these deposits break loose from water piping, rusty water will flow through the faucet.
When iron exists along with certain kinds of bacteria, problems can become even worse. To survive, the bacteria utilize the iron, leaving behind a reddish brown or yellow slime that can clog plumbing and cause an offensive odor. This slime or sludge is noticeable in the toilet tank when the lid is removed.
Since iron combines with different naturally occurring organic materials, it may also exist as an organic complex. The combination of naturally occurring organic material and iron can be found in shallow wells and surface water. This type of iron is usually yellow or brown but may be colorless.
Test Your Water
If there is an iron problem with the water supply, the first step is to determine the source. The source of iron may be from the corrosion of iron or steel pipes or other components of the plumbing system where the acidity of the water, measured as pH, is below 6.5.
A laboratory analysis of water to determine the extent of the iron problem and possible treatment solutions should begin with a test for iron concentration. A water sample kit can be obtained from a certified laboratory. The laboratory’s instructions for collecting the water sample should be followed. Collect the sample as close to the well as possible.
If the source of water is a public water system and you experience iron-related problems, it is important to contact a utility official to determine whether the red water is from the public system or from the home’s plumbing or piping.
The table on the next page lists the treatment methods for the various forms of iron. Before choosing a water treatment method or device, use the attached chart to answer the following questions:
Treatment Methods for Various Forms of Iron
1. Manganese Greensand: A naturally occurring mineral or manufactured material, treated with potassium permanganate that is capable of removing iron; it absorbs dissolved iron and requires chemical regeneration.
2. Catalytic Filtration: A granular filter medium that enhances the reaction between oxygen and iron and then filters the insoluble iron.