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ALUMINUM (Guidance Level = 0.2 mg/L)

Aluminum occurs naturally in water and is also used in water-treatment processes to flocculate suspended particles. No standard has been set, but at high levels it has been suggested that it may cause skeletal and neurological problems.

ARSENIC (MCL = 0.01 mg/L)

Arsenic in water can result from both natural processes and industrial activities, including smelting operations, use of arsenic pesticides and industrial waste disposal. Exposure above MCL may cause skin damage, cancer, or problems with circulatory system. 


Calcium is the major source of “hardness” in water where it can be a nuisance. It builds up on the interior of pipes, water heater coils, boilers, and plumbing fixtures, but it also makes the water taste good, and it is good for you. At low levels, it is helpful in water supplies as it tends to form a coating on pipes and helps prevent corrosion.

CHLORIDE (Guidance Level = 250 mg/L)

There has been a general rise in chloride levels in wells resulting from salt being used for road de-icing. High levels contribute to the corrosiveness of water on pipes and heating equipment. It’s usually accompanied by high sodium levels, which can be a health concern to some individuals.


A failing bacteria test means that Coliform bacteria have been detected in the water. The EPA has designated Coliform bacteria as the indicator organism for safe drinking water. If no Coliforms are found in the water the assumption is made that no other more pathogenic bacteria exist in the water. If Coliform bacteria are detected, it is possible that other harmful (pathogenic) bacteria are present in the water. A result of <1 or <1.1 means that no bacteria were detected.  Frequently bacterial testing is done for both Total Coliforms and Fecal Coliforms or E-Coli. Total Coliforms are the garden variety bacteria present on the surface of the ground. Their presence in well water frequently means that the well is contaminated with surface water due to the drilling process or due to a well construction flaw. Fecal Coliforms or E-Coli come from one source only-the gut of a warm blooded animal such as cows, horses, cats, dogs, rabbits, deer, birds, or humans (septic tank). They do not come from cold blooded animals such as fish, toads, snakes, or insects. The presence of Fecal Coliforms or E-Coli in the water can cause gastrointestinal distress.

COPPER (Guidance Level = 1.3 mg/L)

Water can be a significant source of copper intake depending upon the geographical location, the character of the water, the temperature of the water, and the presence of copper pipes. At concentrations above 1 mg/L copper can cause blue/green staining in laundry and plumbing fixtures and a metallic taste in the water.

FLUORIDE (MCL = 4.0 mg/L)

Fuoride at an optimum level of 1 mg/L has been shown to be effective in reducing dental carries. At levels over 2.4 mg/L it may cause mottling of teeth and bone disease. 


Hardness is a measure of how much lime (calcium and magnesium carbonate) is dissolved in the water. Hard water is generally good tasting and good for you; however it can produce scaling on plumbing fixtures and gives poor sudsing characteristics. A water softener removes the calcium and magnesium and replaces them with sodium. Washing characteristics are improved and scaling is reduced but the water does not taste as good and it is more corrosive to copper pipes.  Fredericktowne Labs measures hardness in mg/l (CaCO3 equivalent). Water is considered to be “soft” or low of hardness if the level is 0-75 mg/l. Moderate hardness is 76-150, hard is 151-250 and very hard is 251 and up. Hardness is sometimes expressed in “grains per gallon”. To change mg/l to grains per gallon, multiply mg/l by 0.058. To change grains per gallon to mg/l multiply the grains per gallon by 17.1.

IRON (Guidance Level = 0.3 mg/L)

Iron in drinking water is a very common aesthetic problem. It is not a health problem. In the aquifer, iron is usually dissolved in water and is not visible. When iron comes in contact with oxygen, it oxidizes to a reddish compound that can discolor bathroom fixtures and laundry. It can also impart a metallic taste to the water.

LEAD (MCL = 0.015 mg/L)

Lead is a relatively rare metal in the earth’s crust. The main source of lead in drinking water is leaching from lead pipes and lead solders used to assemble copper pipes and from brass fixtures. Lead enters drinking water primarily as a result of corrosion of plumbing and fixtures, particularly in areas having soft, acidic waters. The most serious effects associated with markedly elevated blood levels include irreversible brain damage and sometimes death. Children and fetuses are especially sensitive to lead.


Along with calcium, it is a contributor to the hardness of water. See comment on Calcium. Both calcium and magnesium enter the water when it is in contact with limestone. Water softeners remove “hardness” by replacing the calcium and magnesium with sodium. 

MANGANESE (Guidance Level = 0.05 mg/L)

The chemistry of manganese in water is similar to iron with the exception that manganese produces a brownish black discoloration rather than the brownish red of iron. A high level of manganese produces a very unpleasant odor and taste in water and at very high levels can have adverse health consequences.

MERCURY (MCL = 0.002 mg/L)

Almost all mercury detected to date in drinking water is in the form of inorganic mercury. Inorganic mercury is poorly absorbed through the gastrointestinal tract, does not penetrate cell membranes rapidly, and is less toxic than methyl mercury. However, inorganic mercury may cause liver damage. 

NITRATES (MCL = 10 mg/L) & NITRITES (MCL = 1.0 mg/L)

Although nitrates and nitrites occur naturally, the major source of elevated nitrates in drinking water is long term fertilization of agricultural land. Other sources are surface water intrusion from feedlots, barnyards or leaking septic tank. Elevated nitrates can interfere with the transport of oxygen by the blood in the unborn fetus and the very young infant.

pH (Recommended Range 6.5 - 8.0)

pH is a measure of how acidic or alkaline the water is.  EPA recommends that the pH of drinking water be between 6.5 and 8.5.  A pH of 7.0 is neutral.  As the numbers get smaller the acidity increases. “Acid rain” has a pH of about 5. Vinegar has a pH of about 2.5. Coke has a pH of about 3. Numbers greater than 7.0 are considered alkaline. “Draino” has a pH of about 12. Other household products that are alkaline include toothpaste, baking soda, antacids and bleach.  A low pH (less than 6.5) can contribute to copper pipe corrosion but is not considered a health problem.  A low pH can also increase the likelihood of lead being leached from the plumbing pipes.


Orthophosphates are applied to agricultural land or residential cultivated land as fertilizers and are carried into surface waters as runoff which may then penetrate into wells or aquifers. These can indicate a possible contamination of the water by agricultural practices. 


Potassium is an essential element in both plant and human nutrition and occurs in groundwater as a result of mineral dissolution from decomposing plant material, and from agricultural runoff. 

SELENIUM (MCL = 0.05 mg/L)

Selenium occurs naturally in some rocks and soils but can also indicate contamination from mines and refineries. Selenium is an essential nutrient at low levels but at high dose levels it is toxic. 

SODIUM (Guidance Level = 20 mg/L)

A guidance level of 20 mg/L in drinking water is suggested by the EPA for the high risk population of hypertensives and heart patients. Food accounts for approximately 90% of the daily intake of sodium, whereas drinking water contributes up to the remaining 20%.

SULFATE (Guidance Level = 250 mg/L)

Sulfate is found in almost all natural  waters. At high levels it may indicate septic or agricultural leaching into the water supply. Can be a precursor to hydrogen sulfide or “rotten egg” odor and taste in the drinking water.


Trihalomethanes (THM) compounds have been found in most chlorinated water supplies in the US; typically they are produced in the treatment process as a result of chlorination. Toxicological studies suggest that chloroform is a potential human carcinogen. Exposure above MCL may cause liver, kidney or central nervous system problems.

TURBIDITY (Max. 10 ntu)

Turbidity refers to the degree of cloudiness in the water due to suspended particles. It is considered to be an indication of general water quality. High turbidity is frequently seen in newly drilled wells. If turbidity increases after a rain, it can indicate that surface water intrusion is occurring. This frequently causes the well water to be contaminated with bacteria.

Volatile Organic Compounds (VOCs)
Volatile Organic Compounds (VOCs)

VOCs include 58 different organic compounds. None of them occur naturally in water. They can indicate gasoline contamination if Benzene, Ethylbenzene, Toluene, Xylenes, or MTBE are observed, or they can detect other organic compounds and solvents such as methylene chloride, trichloroethylene (TCE), tetrachlorethylene (PERC/PCE), or carbontetrachloride

ZINC (Guidance Level = 5 mg/L)

Zinc most commonly enters the domestic water supply from deterioration of galvanized iron and dezincification of brass. In such cases lead and cadmium also may be present because they are impurities of the zinc used in galvanizing. Zinc in water also may result from industrial waste pollution.


  • MCL stands for “Maximum Contaminant Level”.  It is the highest level of a contaminant allowed in drinking water.  MCL’s are EPA enforceable standards.  EPA has also published non-enforceable guideline levels for contaminants causing cosmetic problems (such as taste, odor or color).  Some states have made these enforceable standards.
  • < stands for “less than” and indicates that the component in question was not detected
  • > stands for “greater than” and indicates that the component was present in an amount greater than what the test could measure.
  • mg/l stands for milligrams per liter and is nearly synonymous with ppm (parts per million).
  • ug/l stands for micrograms per liter and is nearly synonymous with ppb (parts per billion).
  • NTU stands for Nephelometric Turbidity Units  This is a measure of haziness or cloudiness.
  • NPV stands for Non-Productive Visit. This occurs when the Fredericktowne Labs water collector in the course of a scheduled pickup is unable to collect a sample. This can happen if chlorine is present, entry is not possible, or water is not available.

Photo Credit: Aleksandra Sapozhnikova