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Water that Stains



Red stains are normally caused by iron in the water. You must test to determine the amount and the type of iron you have. Some types are: oxidized, soluble, colloidal, bacteria or organic-bound. All are a problem! It only takes 0.3 ppm to stain clothes, fixtures, etc.

Oxidized

This type of iron is usually found in a surface water supply. This is water that contains red particles when first drawn from the tap. The easiest way to remove this type of iron is by a fine mechanical filter. A cartridge type filter is usually not a good solution, due to the rapid plugging of the element. Another method or removal is by feeding a chemical into the water to cause the little particles of iron to clump together and then fall to the bottom of a holding tank, where they can be flushed away.

Soluable

Soluble iron is called "clear water" iron. After being drawn form the well and contacting the air, the iron oxidizes, or "rusts", forming reddish brown particles in the water. Depending on the amount of iron in the water, you may solve this problem with a water conditioner, or a combination of softener and filter. You may use an iron filter that recharges with chlorine or potassium permanganate, or feed chemicals to oxidize the iron and then filter it with a mechanical filter. You can sometimes hide the effects of soluble iron by adding chemicals that, in effect, coat the iron in the water and prevent it from reaching oxygen and oxidizing.

Colloidal

Colloidal iron is the suspension of very small particles of oxidized iron in water. They are usually bound together with other substances. They resist agglomeration, ie, the combining together of like substances forming larger, heavier, more filterable ones, due to the static electrical charge they carry. This iron looks more like a color than particles when held up in a clear glass, as they are so small. Treatment is usually one of two: Feed chlorine to oxidize the organic away from the iron, thus allowing agglomeration to occur, or, feeding polymers that attract the static charge on the particles, forming larger clumps of matter that is filterable.

Bacterial

Iron bacteria are living organisms that feed on the iron found in the water, pipes, fittings, etc. They build slime all along the water flow path. Occasionally, the slimy growths break free, causing extremely discolored water. If a large slug breaks loose, it can pass through to the point of use, plugging fixtures. These types of bacteria are becoming more common throughout the United States. If you suspect bacteria iron, look for a reddish or green slime buildup in your toilet flush tank. To confirm your suspicions, gather a sample of this slime and take it to your local health department, or water department for observation under the microscope. This type of iron problem is very hard to eliminate. You must kill the bacteria, usually by chlorination. You must use high amounts of chlorine throughout your plumbing system to kill all organisms. You may find it necessary to feed chlorine continuously to prevent regrowth. A filter alone will not solve this problem.

Organic bound

When iron combines with tannins and other organics, complexes are formed that cannot be removed by ion exchange or oxidizing filters. This iron may be mistaken for colloidal iron. Test for tannins; if they are present, it is most likely combined with the iron. Low level amounts of this pest can be removed by use of a carbon filter, which absorbs the complex. You must replace the carbon bed when it becomes saturated. Higher amounts require feeding chlorine to oxidize the organics to break apart from the iron and cause both to precipitate into a filterable particle.

Blue or Green Stains indicate copper in your water supply, or you have copper pipes and corrosive water. Test for copper in your water. Test the pH, total dissolved solids content and the oxygen content of your water.

Copper

Copper can be removed by ion exchange, ie, a water softener. The removal rate is about the same as it is for iron.

Copper pipes and corrosive water

If your pH is from 5 to 7, you may raise it by passing the water through a sacrificial media. By sacrificing calcium carbonate into the water, the corrosively will be reduced. If the pH is below 5, you will need to feed chemicals into the water.

If the corrosively is caused by excess oxygen, the hot water will be much more corrosive than the cold. Treatment is by feeding polyphosphate or silicates to coat and protect the plumbing, or to aerate the water to release the excess oxygen.

Prepared by Trevor Croll,

42 Pearse Street, Keperra, Queensland Australia, 4054.
Phone 61 7 3855 1115