Red stains are usually caused by iron in the water. You must test to determine both the amount and the type of iron present. Common types include oxidized, soluble, colloidal, bacterial, or organic-bound iron. All are problematic. It takes only 0.3 ppm to stain clothes, fixtures, and more.
Oxidized Iron
This type of iron is often found in surface water supplies. It appears as red particles when first drawn from the tap. The simplest way to remove oxidized iron is with a fine mechanical filter. A cartridge filter is usually not ideal, as the element plugs quickly. Another method is chemical treatment, which causes the iron particles to clump together and settle at the bottom of a holding tank, where they can be flushed away..
Soluble Iron
Soluble iron, also called clear water iron, appears colourless when drawn from the well. Once exposed to air, the iron oxidizes—or “rusts”—and forms reddish-brown particles. Depending on the concentration, this problem may be solved with a water conditioner, a softener combined with a filter, or a dedicated iron filter recharged with chlorine or potassium permanganate. Chemical treatment can also oxidize the iron so it can be filtered out mechanically. In some cases, chemicals are used to coat the iron, preventing oxidation and reducing staining, though this does not truly remove it.
Colloidal Iron
Colloidal iron consists of extremely small oxidized particles suspended in the water, usually bound with other substances. These particles resist combining into larger, filterable clumps due to their static charge. Colloidal iron often appears more like a tint than visible particles when viewed in a glass. Treatment options include feeding chlorine to strip organics from the iron (allowing agglomeration) or adding polymers that neutralize static charges, enabling filtration.
Bacterial Iron
Iron bacteria are living organisms that feed on iron in water, pipes, and fittings, forming slime along the flow path. When the slime breaks free, it can cause severely discoloured water and clog fixtures. If you suspect iron bacteria, look for reddish or green slime in your toilet flush tank. To confirm, collect a sample and have it examined by your local health or water department.
This problem is very difficult to eliminate. The bacteria must be killed, usually through shock chlorination with high doses throughout the plumbing system. Continuous chlorination may be required to prevent regrowth. Filtration alone will not solve this problem.
Organic-Bound Iron
When iron combines with tannins and other organic compounds, complexes form that cannot be removed by ion exchange or oxidizing filters. This type of iron may be mistaken for colloidal iron. Test for tannins—if they are present, the iron is likely bound.
Low levels can sometimes be treated with a carbon filter, which absorbs the complexes (though the carbon bed must be replaced once saturated). Higher concentrations usually require chlorine feed, which oxidizes the organics and frees the iron to precipitate into filterable particles.
I Have Blue or Green Stains on my Fixtures -- Help!
If you notice blue or green stains, the cause is typically copper in your water supply or copper plumbing reacting with corrosive water.
Copper
Copper can be removed by ion exchange with a water softener. Removal efficiency is comparable to iron removal.
Copper Pipes and Corrosive Water
If the pH is between 5 and 7, it can be raised by passing the water through a sacrificial media such as calcium carbonate, which reduces corrosiveness. If the pH is below 5, chemical feed is usually necessary.
If corrosion is caused by excess oxygen, hot water will corrode more aggressively than cold. Treatment includes feeding polyphosphates or silicates to coat and protect the plumbing, or aerating the water to release the excess oxygen.