Iron is one of the few contaminants that need no water analysis to identify. It is very easy to tell if the water has been contaminated by iron because of the rusty odor and taste it gives off. The level of iron in water has to be extremely high in order to pose a threat to health. If you one can stomach the flavor of the iron-contaminated water, it is most likely safe to drink. Most people that install water filter for iron do so not because of the potential health risk but to get rid of the awful taste and smell.
Like iron, contaminants that belong to the non-health threatening group are more of annoyances rather than threats. Other examples of non-health threatening water contaminants are aluminum, copper, fluoride and manganese. These are all contaminants commonly found in water and pose no real danger unless the contamination level is extremely high.
However, these contaminants can cause all kinds of inconveniences. Iron, for example, can cause the browning of white clothes, affect the cleaning power of detergents and corrosion of pipes. That is why certain measuring equipment must be used to make sure that the amount of this non-health threatening water contaminants is under control.