Iron in water supplies, particularly from groundwater sources, is a common concern for many homeowners. This naturally occurring element can cause various problems that affect water quality and household plumbing. Boiling water is often used to eliminate biological contaminants. The central question is whether this common household practice is an effective way to address the presence of iron.
Forms of Iron Found in Water
Iron exists in water in two primary states that dictate its visibility. The first state is ferrous iron (\(\text{Fe}^{2+}\)), often referred to as “clear water iron” because it is dissolved and invisible to the naked eye. This soluble form is commonly found in groundwater where oxygen levels are low.
The second state is ferric iron (\(\text{Fe}^{3+}\)), known as “red water iron.” This form is insoluble, remaining suspended as tiny, solid particles. It is responsible for the rust-colored, cloudy appearance of water and the reddish-brown sediment that settles at the bottom of a container.
The Impact of Boiling on Iron Content
Boiling water does not physically remove iron; instead, it initiates a chemical process that changes the iron’s state. When water containing dissolved ferrous iron is heated to a boil, it introduces oxygen into the water, a process similar to aeration. This exposure promotes the oxidation of the soluble ferrous iron (\(\text{Fe}^{2+}\)) into the insoluble ferric iron (\(\text{Fe}^{3+}\)).
The heat accelerates this reaction, causing the dissolved iron to convert into a solid precipitate known as ferric hydroxide (\(\text{Fe}(\text{OH})_{3}\)). The water will often develop a cloudy, reddish-brown tint as the particles form. Once the water cools, this newly formed particulate iron will settle to the bottom of the container.
This process is often mistaken for removal, but the total amount of iron in the water remains unchanged. Unlike volatile contaminants, iron concentrates as the water evaporates. Boiling only makes the iron visible and capable of settling, requiring a subsequent step like decanting or filtration to achieve actual physical separation.
Consequences of High Iron Levels
The presence of high iron concentrations in household water causes significant aesthetic and infrastructure issues. Concentrations as low as 0.3 milligrams per liter can result in reddish-brown or rust-colored staining on plumbing fixtures, sinks, and laundry. These stains are notoriously difficult to remove and can permanently discolor fabrics and surfaces.
Iron also imparts an unpleasant metallic taste to the water, which can affect the flavor of beverages and cooked vegetables. Furthermore, the iron particles can accumulate over time, leading to the clogging of pipes, showerheads, and water-using appliances. This buildup can reduce water flow and decrease the efficiency and lifespan of household equipment.
Alternative Home Treatment Options
Since boiling only changes the form of iron, homeowners must rely on proven treatment technologies for true removal. The most appropriate method depends on the type of iron present, which can be determined through water testing.
For water containing insoluble ferric iron, simple sediment filtration is the most direct solution. These systems use a physical barrier, such as a cartridge filter, to trap the suspended particles before they enter the home’s plumbing. This method is effective because ferric iron is already in a particulate form.
Treating dissolved ferrous iron requires a two-step approach: oxidation followed by filtration. Oxidation systems introduce an agent, such as air (aeration), chlorine, or potassium permanganate, to chemically convert the soluble ferrous iron into insoluble ferric iron. The newly created solid iron particles are then captured and removed by a specialized filter.
Another effective alternative for dissolved iron is an ion exchange water softener. While primarily designed to remove hardness minerals, these systems can also remove lower concentrations of ferrous iron. The iron ions are exchanged for sodium or potassium ions as the water passes through a resin bed, effectively removing the dissolved iron from the water.