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Treatment for Rust in Water

Rust is caused by high levels of iron in water. However, the treatment for this varies with the type and source of iron and the resources and time available.

  1. Sources of Rust

    • Rust forms when iron reacts with water to create iron oxide, more commonly known as rust. Iron makes up 5 percent of the Earth's crust and enters the water cycle by seeping into aquifers (ground water supplies). When iron quantities rise above 0.3 mg/l then the water becomes red in color. An alternative, less common, source of iron is from pipes which have corroded over time, releasing iron into the water system.

    Types of Iron

    • Two types of iron occur in water, soluble ferrous iron or insoluble ferric iron. The former will only turn the water red after exposure to air (initially the water will be clear) and the latter will give the water an immediate red tint. Fve types of treatment are available; the type to select depends on the level and type of iron.

    Option 1: Phosphate Treatment

    • This is used for low iron levels and requires you to have access to the source (e.g. the well). You should inject phosphate compounds into the water between the well and the pressure tank. This treatment ensures the iron remains dissolved and is low cost. However, compounds can become unstable at high temperatures and they contribute to high levels of nutrients in surface water which is detrimental to the environment.

    Option 2: Ion Exchange Water Softener

    • This can be used for medium iron contents of 1 to 5 mg/l and works by replacing the iron with sodium. It is the same device used to remove water hardness and so can act as a dual treatment if needed. It is important to check the manufacturer's recommendations as not all water softeners remove iron and, if the recommended concentration of iron is exceeded, the softener will become clogged. This treatment raises the sodium content in the water and so is not recommended for people with high blood pressure.

    Option 3: Oxidizing Filter

    • This treatment works for dissolved iron levels of up to 15 mg/l. Filters vary depending on the amount of dissolved oxygen in the water and so this needs to be tested first. The filters normally use manganese greensand which absorbs the iron.

    Option 4: Pressure-Type Aerator

    • This is used for high levels of dissolved iron and works by oxidizing iron into a solid form by mixing it with air. It is not recommended for water containing organic iron complexes.

    Option 5: Oxidation and Filtration

    • Used for high levels of iron only, this treatment uses chlorine (or another oxidizing agent) to oxidize iron to a solid form before removing it using a sand filter. This treatment is recommended when iron bacteria are present. Unfortunately, this makes your water taste of chlorine.

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