Authors: Blake Ross, Extension Specialist, Agricultural Engineering, and Kathleen Parrott, Extension Specialist, Housing.
Publication Number 356-489, April 1998
Water Testing Terms
Acidic
A descriptive term used in reference to water having a pH of less than 7; pertains to the corrosiveness of water.
Acute Health Effects (acute toxicity)
Any poisonous effect with a sudden and/or severe onset produced within a short period of time after using contaminated water, resulting in mild to severe biological harm or illness. Acute symptoms include, but are not limited to, upset stomach, loose stool, bowel upset, and gastrointestinal difficulties. If symptoms occur as a result of drinking contaminated water, medical attention should be sought promptly.
Aesthetic Characteristics
The nonhealth-related characteristics of water which make it desirable for human use. Generally taste, color, odor, and turbidity are considered to be aesthetic characteristics.
Alkaline
A water sample having a pH greater than 7 is alkaline (non-acidic).
Carcinogenic
Capable of causing cancer.
Certified Testing Laboratory
A lab listed by the Virginia Division of Consolidated Laboratory Services as qualified to test drinking water in Virginia. Information about local state-approved labs is available at local Virginia Cooperative Extension or Health Department Offices.
Chronic Health Effects
Chronic means long-term. Chronic health effects occur and persist as a result of repeated or longterm use of contaminated water. Often, it takes a lifetime of exposure for chronic health effects to occur. Chronic health effects include irreversible damage to internal organs, and mutagenic effects (changes in the gene structure) which can result in cancer, birth defects, disabilities, and other problems.
Coliform Bacteria
A type of bacteria found in large numbers in the intestinal tracts of humans and animals. Coliform bacteria are used as an indicator test“if the coliform count is unacceptable, it is an indicator that the water is polluted and that further tests for other bacteria or pathogens would be advisable.
Concentration
The amount of a given substance (weight) in a specific amount of water (volume).
Contaminants
Substances that make water unfit for drinking and/ or other household uses; used interchangeably with pollutants.
Corrosive Water
Water that is acidic and "soft" may be corrosive and may deteriorate plumbing and leach toxic metals such as lead and copper from pipes.
Detection Limit
The minimum concentration of a substance that may be measured and reported in the given testing method. Many lab reports will state what the detection limit is for each contaminant.
Disinfection
The destruction of all pathogenic organisms.
EPA
The abbreviation for the Environmental Protection Agency, properly called, "the United States Environmental Protection Agency." This agency has the responsibility of developing and enforcing Primary Drinking Water Standards. The EPA also develops, but does not enforce, Secondary Drinking Water Standards.
Grains per Gallon (gpg)
Apothecaries' weight of a chemical substance in one gallon of water used in the water-conditioning trade to indicate hardness of water. One gpg equals approximately 17 mg/L hardness.
Hardness
A major water quality problem in western Virginia. Hardness is a relative term. It describes the content of the dissolved minerals, calcium and magnesium, and is reported as grains per gallon. Water with less than 3.5 grains per gallon is considered "soft"; while hard water above 7 grains per gallon may affect the appearance of plumbing fixtures, the lifespan of water heaters, and the effectiveness of detergents.
Health Risk
The risk or likelihood that a chemical will adversely affect a person' s health. Estimating health risks is a complex and inexact science.
Heavy Metals
Elements with higher molecular weights which are generally toxic in low concentrations to plant and animal life. Examples include mercury, chromium, cadmium, arsenic, and lead. Heavy metals are often found in runoff from industrial sites, hazardous waste disposal and landfills.
Hydrogen Sulfide
A hazardous, suffocating gas that smells like rotten eggs when it escapes from water, and will result from sulfates in the water.
Iron Bacteria
Microorganisms that feed on iron in the water. They may appear as a slimy rust-colored coating on the interior surface of a toilet flush tank or as a glob of gelatinous material in the water.
Maximum Contaminant Level (MCL)
The maximum level of a contaminant which is permitted in public water supplies. Maximum contaminant levels are specified in the Primary Drinking Water Standards set by EPA for contaminants that affect the safety of public drinking water.
Milligrams per Liter (mg/ L)
Metric weight of a substance in a liter of water. 1 mg/ L = 1 ounce per 7,500 gallons. (1 mg/L = approximately 1 ppm in water).
Most Probable Number (MPN)
An index expression used in the multiple-tube fermentation-testing procedure to indicate the presence of coliform bacteria in a sample of water. MPN is a "most probable number," or estimate, rather than an actual count of microorganisms.
Nitrate
A salt form of the chemical, nitrogen. The presence of nitrates in a water supply generally indicates contamination by human or animal waste, and/or commercial fertilizer.
Nuisance Contaminants
Contaminants which affect aesthetic or functional aspects of water quality and have little or no impact on health. They are managed by setting Secondary Maximum Contaminant Level Standards.
Organic Chemicals
Those chemicals which contain carbon. Historically, organic compounds were obtained from vegetable or animal sources. Today, many organic chemicals are synthesized in a laboratory. Organic chemicals which can contaminate water supplies include trihalomethanes, pesticides, and volatile organic chemicals.
Parts per Million (ppm)
Concentration of a substance on a weight basis in water. 1 ppm = 1 pound of a contaminant per million pounds of water (I ppm in water = approximately 1 mg/L).
Pathogens
Live organisms which contaminate water such as bacteria, viruses, and parasites.
pH
A factor used to measure the acidity and alkalinity of water. Values for pH fall on a scale ranging from O to 14. Water that has a pH of 7 is neutral; water that is acid has a pH lower than 7 and water that is alkaline has a pH greater than 7. The secondary standard for drinking water is a pH between 6.5 and 8.5.
Pollutants
Natural or man-made substances that make water unfit for human consumption or use.
Potable Water
Water fit for drinking.
Primary Standards
The Primary Drinking Water Standards are published, monitored, and enforced by the EPA. Primary standards regulate contaminants which pose serious health risks to the water user. The primary standards are only enforceable in public water systems.
Private Water Systems
Any systems which do not meet the definition of public water systems, for example, a private individual water source, such as a backyard well. Private water systems are not regulated by VDEQ or EPA standards.
Public Water System
In Virginia, a public water system is one that serves at least 15 connections (for example households) or at least 25 individuals. VDEQ and EPA regulations apply to public water systems.
Pure
Without contaminants.
Radon
A tasteless, odorless, colorless radioactive gas formed from decay of radium in rocks that has been found dissolved in some groundwater supplies. Though it can be swallowed in a glass of water, it is most dangerous when inhaled. Activities that release radon as vapor from water include showering, bathing, and cooking. Radon is known to be carcinogenic and is linked with increased risk of lung cancer.
Safe
The level of contaminants, if any, is low enough that no health problems will occur.
Saturation Index
One of the methods (see Stability Index) for assessing the scale-dissolving (corrosive) or scaleforming potential of water. A positive number indicates a tendency to deposit calcium carbonate. If the result is negative, it is an indication that the water will dissolve calcium carbonate and enhance corrosion.
Scale
Mineral deposits which build up on the inside of water pipes and water-using appliances, like coffee pots. Scale is primarily composed of calcium carbonate and usually associated with hard water.
Secondary Standards
The Secondary Drinking Water Standards are published by the EPA. Secondary Standards set desirable/ acceptable levels for nuisance contaminants which affect taste, odor, color, and other aesthetic and functional qualities of the water supply. These secondary standards are not enforced by law, but rather are guidelines for municipal water treatment plants and state governments.
Stability Index
One of the methods (See "Saturation Index") for assessing the scale-forming or scale-dissolving potential of water; an index of about 6.0 or less indicates scale-forming tendencies, an index of 7.5 to 8.0 shows scale-dissolving (corrosive) tendencies.
Total Dissolved Solids (TDS)
A good general indicator of water quality which measures the total amount of dissolved minerals, metals, and salts. Water with more than 500 milligrams per liter TDS is of poor quality and may contain undesirable amounts of calcium, magnesium, sulfates, chlorides, or other substances.
Toxic Metals
Arsenic, barium, chromium, mercury, selenium, silver, and other toxic metals are regulated by Primary Drinking Water Standards. Toxic metals may be naturally occurring in rock and soil, or may contaminate water as a result of runoff or leaching from industrial or agricultural sites or hazardous waste disposal.
Toxicity
The toxicity (poisonous effect) of a water contaminant depends on the concentration of the contaminant in the water and the period of time the contaminated water is consumed. Any chemical can be toxic, if you swallow enough of it. Also, people react differently to different toxic substances; some people may be harmed more than others. Pregnant and nursing women, the elderly, infants, ill or malnourished people, and people taking medication may be especially vulnerable to certain contaminants.
Trihalomethanes
Organic chemicals which can form when residual chlorine from treated drinking water combines with traces of bromine and natural organic materials.
Turbidity
A cloudy condition in water due to suspended silt or organic matter.
VDEQ
The abbreviation for the Virginia Department of Environmental Quality. The VDEQ is responsible for developing, monitoring, and enforcing Virginia' s water quality standards.
Volatile Organic Chemicals (VOCS)
Synthetic compounds which evaporate readily and are difficult and expensive to detect. Primary Drinking Water Standards set limits for several volatile organic chemicals, including the solvents such as trichloroethylene and carbon tetrachloride, and the gasoline component, benzene. Tests for synthetic organic chemicals are not routine and tend to be fairly expensive because of the difficult and precise laboratory work involved.
Water Quality
Determined by these characteristics: safety, taste, color, smell, corrosivity, staining, and hardness.
Interpreting Your Water Test Report