Iron is one of the most common elements in the Earth's crust and dissolves in underground water. This carries the iron into the water supply as ground water seeps into aquifers. Iron can be found in drinking water as ferrous iron which is soluble and ferric iron which is insoluble. You can determine if you need to have the iron concentration in your water measured by observing its color and other properties.
Pour water in a clear container and allow it to stand. An iron concentration of as little as 0.3 milligrams per l (mg/l) may be sufficient to produce reddish brown sediment. Iron is not generally harmful at this level, so an unhealthy level of iron in the water is easily detectable.
Detect ferrous iron if the water is completely clear and the reddish brown sediment doesn't appear until after the water is allowed to stand. The presence of ferrous iron indicates that the water's hardness should be checked, especially if any users are on a sodium restricted diet.
Observe water with a red or yellow color as soon as it comes from the tap. This indicates the presence of ferric oxide if the color remains after the iron particles fall to the bottom of the glass. Ferric oxide may indicate inadequate water pressure or dissolved organic matter.
Check your plumbing for a reddish brown or yellow sludge, possibly accompanied by an unpleasant odor. This can indicate the presence of iron-producing bacteria, which will typically require a shock treatment of chlorine followed by prolonged chlorination.
Check for water with a brown or yellow color when the water source is groundwater. This can indicate the presence of organic iron which can require treatment with activated carbon.