Iron in Drinking Water
Iron is present in many water supplies. Iron comprise 5% of the Earth's crust and for that reason Iron is especially prevalent in ground water supplies such as drilled wells. When ground water percolates through this rock it dissolves small quantities of the iron. Iron is rarely present in water at concentrations greater than 10 ppm however concentrations as low as 0.3 ppm are enough to stain drinking water a reddish brown colour and cause many issues for the homeowner.
Iron can be present in two forms in water. "Clear water iron" or ferrous iron which is the soluble form and the insoluble ferric form. Ferrous iron is completed dissolved when it is in the groundwater source. As this ferrous iron is dispensed in the home it becomes exposed to oxygen, oxidation occurs, and the iron changes from dissolved iron to the non-dissolved ferric iron. This change from ferrous to ferric iron may take place at different locations within the water system. Where this change occurs is a function of temperature, pH, oxygen concentrations, and time.
While iron in water is not a health concern, it can drastically affect water taste and usability. Iron imparts a very distinct metallic taste to water, and iron in water will stain sinks, bathtubs and toilets a reddish brown color eventually fouling them to the point that they need to be replaced. Iron in water can also act as a food source for iron metabolizing bacteria. These bacteria use the iron as their primary food source creating black slimy colonies that may line pipes and toilet bowls.
Removing iron from a water supply is first an exercise in determining the type of iron which is present. The test is quite straightforward. Fill a 5 gallon white pail with water from your home. If the water dispensed has a visible tint to it, the iron is most likely ferric iron - the non-dissolved form of iron. If the water dispensed is first clear, but then over time becomes cloudy and/or reddy brown in color, and/or particles settle to the bottom, the iron present is most likely dissolved iron (ferrous iron).
Ferrous iron is the most common form of iron encountered with drilled wells. Ferrous iron in low quantities (less than 2.0 ppm) can be removed quite well using a water softener. For higher quantities of ferrous iron, or to remove ferric iron, the best way is to use a dedicated iron water filter that expose the water oxygen to cause it to change to its particulate form, and then filter the particles out of the water. Once the filter becomes saturated with iron, it backwashes sending all the iron to drain. Where a water softener or iron water filter cannot be used, Pentek Water Filtes offers a cartridge system that will do a good job for low iron concentrations.
The best thing any homeowner can do when presented with a possible iron problem, is to have the water tested by an accredited laboratory. A "metals scan" is usually sufficient in determining the water chemistry and this makes the choosing of a much more straightforward process.
