acid
Water that contains substances that lower the pH value below 7.0 (neutral).

acidity
The capacity for neutralizing an alkaline substance.

alkaline
Water that contains substances that raise the pH value above 7.0 (neutral).

alkalinity
The capacity for neutralizing an acid.

acute, chronic
Bacteria in water can cause immediate symptoms of flu or intestinal distress. Such acute illnesses are generally of the highest priority among water utility managers, who are less concerned with longer-term, poorly understood chronic disorders that result from exposure to metals, industrial chemicals, and pesticides. Acute cases are rarely fatal, and thousands of U.S. cases of water-based ailments such as cramps, diarrhea are probably never reported to physicians.

acquifer
An underground body of water that is more protected from contaminants than surface, but is still susceptible to perils such as fecal coliform  from septic tanks. Half of all Americans get drinking water from such underground sources. Of these, roughly a third have their own wells, which are not regulated by government. The remainder use municipal water systems, which draw on underground supplies that are subject to the same rules as surface water.

action levels
With some contaminants, the [EPA] does not establish hard and fast levels allowed in water supplies, but does set a course of events for the most extreme cases.  Lead is an example of a water pollutant that has no primary or secondary standards but does have an action level that is calculated on a community-wide basis.

bacteria
Single-cell organisms that can reproduce in the human gut and cause vomiting and diarrhea, bacteria also cause acute health problems that can kill AIDS and cancer patients. 


chloride
Chloride imparts a salty taste, and can indicate contamination from sea water, brackish water, or salt storage.

chlorine
Chloride may make your water taste salty and indicates contamination from an outside source such as salt storage, seawater, or septic waste.

chlorinated pesticides
Commonly used agricultural pesticides. Some people who drink water contaminated with these compounds could experience problems or damage to the eyes, liver, kidneys, or spleen and may have an increased risk of getting cancer.

Alachlor
Aldrin
Atrazine
alpha-BHC
beta-BHC
delta-BHC
Chlordane
p,p-DDD
p,p-DDE
p,p-DDT
Dieldrin
Endosulfan I
Endosulfan II
Endosulfan Sulfate
Endrin
Endrin Aldehyde
Endrin Ketone
Heptachlor
Heptachlor Epoxide
Hexachlorobenzene
Hexachlorocyclopentadiene
Lindane (gamma-BHC)
Methoxychlor
Toxaphene

coliform bacteria
Indicates contamination from an unsanitary condition such as septic waste or surface water entering the water supply. Health effects include gastrointestinal illness, cryptosporidium and giardia lamblia.

color
Determines the coloration level. MCL - 5 units.

copper
Usually associated with the corrosion of copper pipes. Can cause stomach or gastrointestinal illness, liver and kidney damage and anemia.

cryptosporidium
A protozoan one-half as large as a red blood cell, cryptosporidium is so small and tough that it is very hard to detect, much less kill. It causes acute health problems in healthy individuals and may be fatal to individuals whose immune systems are compromised by illness, old age, or medical treatments. 


dis-infection
To water experts, dis-infection is a general process to kill living organisms. It does not refer to the removal of unwelcome chemical compounds in the water supply.

distillation
Distillation refers to the boiling of water to make steam, which is then collected and condensed for drinking.

environmental estrogens
These are man-made chemicals, including PCBs, dioxin and triazines, that can cause chronic reproductive and behavioral problems in animals. The molecules of environmental estrogens are chemically similar to natural hormones and trigger subtle hormonal changes, especially in the fetus in early stages of human development. The effects in man are still much disputed by scientists. Some researchers believe these chemicals are responsible for learning disabilities, attention-deficit disorder, breast cancer, and low sperm counts. See the book [Our Stolen Future] for more information.

fecal coliform Bacteria from excrement, fecal coliform are not necessarily harmful by themselves, but are indicative of the presence of other disease-causing organisms that may cause diarrhea, vomiting, or a more serious illness.

fecal streptococcus
These are another group of bacteria that indicate human or animal waste. In some situations, these bacteria survive better than Total or Fecal Coliform. Therefore, they are useful as an indicator of human or animal waste contamination.

filtration, flocculation, sedimentation
Filtration is the process by which water is forced through sand beds. Flocculation is the process by which chemicals are added to the water, causing tiny clumps of debris to form. Sedimentation is the process of removing the flocculate matter.

first draw
This term refers to water that has been sitting in pipes or plumbing fixtures overnight and is first drawn when taps are opened in the morning. Such samples will usually have the highest levels of lead contamination. In homes with severe lead problems, first-draw readings for lead may be three times as high as purged-line samples.

fluoride
Added to many municipal water supplies, also found naturally. Excessive levels may damage teeth.


GAC
This acronym stands for granulated activated carbon, an inexpensive treatment technology by which water passes through grains of carbon. Compared with more expensive solid-block models, GAC filters sometimes affect mostly the taste and smell of water.

ground water
Water from a well or underground acquifer.

hardness
Calcium and magnesium are the main hardness minerals. Although hardness is not a health threat, excessive levels may be harmful to plumbing fixtures and pipes. White deposits around faucets and on dishware are often caused by excessive hardness.


hemochromatosis
An often overlooked ailment associated with iron in drinking water.

immune system
The immune system is the body's way of identifying and destroying diseases, intruders, or foreign cells. The immune system weakens with age, and during medical treatments for some cancers and organ transplants. Persons with Acquired Immune Deficiency Syndrome (AIDS) can have particularly weakened immune systems that are vulnerable to organisms such as cryptosporidiu. The EPA and the Centers for Disease Control (CDC) advise people with such immune deficiencies to boil their water.

iron
Usually comes from a natural source. High levels of iron may cause a bad taste in the water and cause severe staining of laundry and plumbing fixtures. Excessive iron can be a health risk to people with a medical condition known as hemochromatosis.

lead
Usually comes from corrosion of pipes and plumbing fixtures. Causes numerous health disorders and reduced IQ scores. 

manganese
Naturally occurring metal. Not usually considered a health threat. Can cause brownish-black stains on laundry, dishes, and fixtures.

maximum contaminant level (MCL)
The MCL is the amount of a water contaminant which must be reported to state authorities if discovered by a local water treatment plant .


nitrate
Comes from natural decay of organic matter and agricultural runoff. Nitrate causes decreased oxygen carrying capacity in infants and some adults. This can lead to methemoglobinemia (blue baby syndrome). High levels of nitrate indicate possible contamination from agriculture and suggest the need for pesticide testing.

nitrite
Similar to nitrate, however nitrite can cause decreased oxygen carrying capacity in anyone.

odor
Determines the odor level. MCL - 5 units.


PCB's
Environmentally persistent compounds that were used in electronic components and some well pumps. They can cause an increased cancer risk.

Aroclor 1016
Aroclor 1221
Aroclor 1232
Aroclor 1242
Aroclor 1248
Aroclor 1254
Aroclor 1260

pH
Indicates whether water is acidic or basic. Acidic water can cause corrosion of plumbing and fixtures, which leads to elevated levels of metals such as lead and copper. High pH can cause scaling of the plumbing system.

point-of-use or -entry
These are two terms the plumbing industry uses to describe the equipment homeowners use to filter their own water. Point-of-use filters, typically used in the kitchen, apply to water used only for drinking. Point-of-entry devices, often placed in the basement, treat water that is used throughout a home.

primary or secondary standards
The EPA divides contaminants into many lists, charts and tables. Some contaminants are dubbed primary, while others are labeled secondary. But the only contaminants that require immediate notification of the public are bacteria and nitrates. 

purged line
A faucet that has been opened and allowed to run for a specified length of time, usually 1-5 minutes.

radon
Radon is a naturally occurring radioactive gas. The worst exposure to radon probably occurs when a person takes a shower.

reverse osmosis
Reverse osmosis is a [purification] process by which water flows over a membrane that blocks contaminants. Reverse osmosis membranes must be cleaned periodically or replaced. This technology wastes significant amounts of water. Reverse osmosis is available as a point-of-use or entry system.

spring water
According to the U.S. Food and Drug Administration, spring water is water that comes out of the ground on its own or is bottled near water that comes out of the ground on its own.

surface water
Water from rivers and lakes. Roughly half of all Americans get drinking water from surface water sources. 

sulfate
Naturally occurring but can indicate outside contamination of the water supply. Causes gastrointestinal discomfort in individuals who are not accustomed to drinking the water.

trace metals
Trace metals may come from industrial contamination or natural deposits. They can cause increased cancer risk, damage to organs and changes in blood chemistry.

Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromium
Mercury
Selenium
Thallium

triazines
Triazines are herbicides, or weed killers, that are used on a variety of U.S. crops, including grains and citrus. Triazines are currently present in both ground and surface waters. They're banned in Europe; the U.S. Environmental Protection Agency is reviewing two triazines--atrazine and simazine--but is unlikely to ban them. These and other triazines are a cheap way for farmers to kill a wide range of weeds.

VOC's
Compounds which are found in many household products, paints, petroleum products and industrial solvents. People who drink water containing these compounds in excess of the MCL could experience damage to liver, kidneys, spleen, or circulatory system, or changes in the blood. There is also an increased risk of cancer associated with most of these compounds.

benzene
carbon tetrachloride
chlorobenzene
o-dichlorobenzene
p-dichlorobenzene
1,2-dichloroethane
1,1-dichloroethylene
cis-1,2-dichloroethylene
trans-dichloroethylene
dichloromethane
1,2-dichloropropane
ethylbenzene
styrene
tetrachloroethylene
1,2,4-trichlorobenzene
1,1,1-trichloroethane
1,1,2-trichloroethane
trichloroethylene
toluene
vinyl chloride
xylenes
total trihalomethanes