MML tests water and waste water for many different properties, but here is a list of the common contaminates found in drinking water that you should test for in your home and manufacturing facilities water. Common Contaminants Found in Residential Well Water Well water can become contaminated without any change in the water’s taste, smell or appearance. The following are common contaminants found in residential wells throughout the United States: COLIFORM BACTERIA. A natural part of the microbiology of soils, insects, and warm blooded animals, coliform bacteria is the primary indicator for the presence of disease-causing organisms in water. NITRATES. Elevated levels can be an indication of contamination by farm chemicals, lawn fertilizers, or septic saturation. Nitrates can pose a serious health risk to infants. ARSENIC. This toxic element is found naturally in soil and bedrock, but occurs in particularly high levels in Northeast Wisconsin. Ingestion can lead to serious health problems. LEAD. Houses built before 1985 may contain lead pipes or lead-based solder. Lead can cause serious health problems in young children. FLUORIDE. Found naturally in water. While low levels of fluoride are desirable, excessive amounts may stain teeth. SULFATES. High levels of sulfates can cause odors, leave spots, taste bitter and have a temporary laxative effect. CHLORIDES. Small amounts of salt are natural. Higher levels are unnatural and may indicate a faulty water softener, road salt, septic waste or fertilizer contamination.