The presence of coliform bacteria which are a group of micro organisms in drinking water suggest contamination from a surface or shallow subsurface source such as cesspool leakage, barnyard runoff or other source. The presence of these bacteria indicate that disease-causing (pathogenic) organisms may enter the drinking water supply in the same manner if preventive action is not taken. Drinking water should be free of Coliform.

Cysts and viruses are microbiological contaminants, usually found in surface water supplies.

Nitrate in drinking water supplies may reduce the oxygen carrying capacity of the blood (cyanosis) if ingested in sufficient amounts by infants under 6 months of age. This could cause a disease called "methemoglobinemia", or "blue baby" syndrome. If you have high nitrate water, either treat it with an approved treatment methodology or find another source: Boiling will only make it worse!

Lead is now known to leach from older sweat joints in copper pipe. As the water sits in the pipes, small amounts of lead 'dissolve' into the water, contaminating it. Lead is particularly harmful to small children as they more rapidly absorb the toxic substance into their systems.