Definitions of Water Quality Terms
pH (Acidity) - pH is a measure of the
acidity of a solution, in terms of activity of hydrogen ions (H+).
Total Alkalinity - Alkalinity or AT is a measure of the ability of a
solution to neutralize acids to the equivalence points of carbonate or
Nitrate - Nitrates such as potassium nitrate (saltpeter) and ammonium
nitrate are important nitrogen carriers in fertilizers
Nitrite - Sodium nitrite is used for the curing of meat because it
prevents bacterial growth and, in a reaction with the meat's myoglobin,
gives the product a desirable dark red color. Because of the toxicity
of nitrite (lethal dose of nitrite for humans is about 22 mg per kg
body weight), the maximum allowed nitrite concentration in meat
products is 200 ppm.
Total Hardness - Hard water is water that has a high mineral content
(water with a low mineral content is known as soft water). This
content usually consists of high levels of metal ions, mainly calcium
(Ca) and magnesium (Mg) in the form of carbonates, but may include
several other metals as well as bicarbonates and sulfates.
Free Chlorine - Free available chlorine (FAC). The portion of the
total chlorine remaining in chlorinated water that has not reacted
with contaminants — and is "free" to go to work to kill bacteria and
other contaminants. Make sure your test kit can measure FAC; many only
test for total chlorine.
Combined Chlorine - Combined available chlorine (CAC) or chloramines.
The portion of chlorine in the water that has reacted and combined
with ammonia, nitrogen-containing contaminants and other organics such
as perspiration, urine and other swimmer waste. Some chloramines can
cause eye irritation and chlorine odors.
Total Chlorine - The sum of both the free available and combined
Iron - Iron is essential to all known organisms. It is mostly stably
incorporated in the inside of metalloproteins, because in exposed or
in free form it causes production of free radicals that are generally
toxic to cells. To say that iron is free doesn't mean that it is free
floating in the bodily fluids. Iron binds avidly to virtually all
biomolecules so it will adhere nonspecifically to cell membranes,
nucleic acids, proteins etc. The main drawback to iron and steel is
that pure iron, and most of its alloys, suffer badly from rust if not
protected in some way. Painting, galvanization, plastic coating and
blueing are some techniques used to protect iron from rust by
excluding water and oxygen or by sacrificial protection.
Copper - There are numerous alloys of copper — speculum metal and
bronze are copper/tin alloys, and brass is a copper/zinc alloy. Monel
metal is a copper/nickel alloy, also called cupronickel. While the
metal "bronze" usually refers to copper/tin alloys, it also is a
generic term for any alloy of copper, such as aluminium bronze,
silicon bronze, and manganese bronze.
Pesticide - A pesticide may be a chemical substance or biological
agent (such as a virus or bacteria) used against pests including
insects, plant pathogens, weeds, mollusks, birds, mammals, fish,
nematodes (roundworms) and microbes that compete with humans for food,
destroy property, spread disease or are a nuisance. Pesticides are
usually, but not always, poisonous to humans. Pesticides can also be
classed as synthetic pesticides or biological pesticides, although the
distinction can sometimes blur. A systemic pesticide is a pesticide
applied to a plant which is absorbed into its sap and so distributed
throughout the plant to make all parts of it poisonous to pests,
without harming the plant, although systemic insecticides which poison
pollen and nectar in the flowers may kill needed pollinators.
Hydrogen Sulfide - Hydrogen sulfide is a colorless, toxic, flammable
gas that is responsible for the foul odor of rotten eggs and
flatulence. It often results when bacteria break down organic matter
in the absence of oxygen, such as in swamps, and sewers (alongside the
process of anaerobic digestion). It also occurs in volcanic gases,
natural gas and some well waters.
Chloride - The salts of hydrochloric acid HCl contain chloride ions
and are also called chlorides. An example is table salt, which is
sodium chloride with the chemical formula NaCl. In water, it dissolves
into Na+ and Cl- ions.
Sulfate - Sulfates occur as microscopic particles (aerosols) resulting
from fossil fuel and biomass combustion. They increase the acidity of
the atmosphere and form acid rain.
Iron Bacteria - In the management of water-supply wells, iron bacteria
are bacteria that derive the energy they need to live and multiply by
oxidizing dissolved ferrous iron (or the less frequently available
manganese and aluminium). The resulting ferric oxide is insoluble, and
appears as brown gelatinous slime that will stain plumbing fixtures,
and clothing or utensils washed with the water carrying it, and may
contribute to internal corrosion of the pipes and fixtures the water
flows through. They are known to grow and proliferate in waters
containing as low as 0.1mg/l of iron. However, at least 0.3 ppm of
dissolved oxygen is needed to carry out oxidation. The proliferation
of iron bacteria, in some way, increases the chance of sulfur bacteria
infestation. Common effects of excess iron in water are a
reddish-brown color, stained laundry and poor tasting coffee. An
equally common but less well understood problem is infestation of
water supplies with iron bacteria.
Lead - A soft, heavy, toxic and malleable poor metal, lead is bluish
white when freshly cut but tarnishes to dull gray when exposed to air.
Lead is used in building construction, lead-acid batteries, bullets
and shot, and is part of solder, pewter, and fusible alloys. Lead is
also poisonous. Lead poisoning was recognized even by the ancients.
Similarly, in the Twentieth Century, the use of lead in paint pigments
was ended because of the danger of lead poisoning, especially to
children. By the mid-1980s, a significant shift in lead
end-use patterns had taken place. Much of this shift was a result of
the U.S. lead consumers' compliance with environmental regulations
that significantly reduced or eliminated the use of lead in nonbattery
products, including gasoline, paints, solders, and water systems.
Recently, lead use is being further curtailed by the RoHS directive.
Arsenic - Arsenic and its compounds are used as pesticides,
herbicides, insecticides and various alloys. as an insecticide on
fruit trees (resulting in brain damage to those working the sprayers)
The application of most concern to the general public is probably that
of wood which has been treated with chromated copper arsenate ("CCA",
or "Tanalith", and the vast majority of older "pressure treated"
wood). CCA timber is still in widespread use in many countries, and
was heavily used during the latter half of the 20th century as a
structural, and outdoor building material, where there was a risk of
rot, or insect infestation in untreated timber. Although widespread
bans followed the publication of studies which showed low-level
leaching from in-situ timbers (such as children's playground
equipment) into surrounding soil, the most serious risk is presented
by the burning of CCA timber. Recent years have seen fatal animal
poisonings, and serious human poisonings resulting from the ingestion
- directly or indirectly - of wood ash from CCA timber (the lethal
human dose is approximately 20 grams of ash).
Asbestos - Asbestos is used in brake shoes and gaskets for its heat
resistance, and in the past was used on electric oven and hotplate
wiring for its electrical insulation at elevated temperature, and in
buildings for its flame-retardant and insulating properties, tensile
strength, flexibility, and resistance to chemicals. The inhalation of
some kinds of asbestos fibers, however, can cause various serious
illnesses, including cancer. Many uses of asbestos are banned in many
Drinking Water Contaminants
Drinking water, including bottled water, may reasonably be expected to
contain at least small amounts of some contaminants. The presence of
contaminants does not necessarily indicate that water poses a health
risk. EPA sets standards for approximately 90 contaminants in drinking
water. EPA's standards, along with each contaminant's likely source
and health effects, are available at www.epa.gov/safewater/mcl.html.
More detailed information on specific contaminants is available below:
Microbes ~ Radionuclides ~ Inorganics ~ Volatile Organics ~ Synthetic
Organics ~ Disinfectants ~ Disinfection Byproducts ~ MTBE ~ Health
are common in the environment and are generally not harmful. However,
the presence of these bacteria in drinking water is usually a result
of a problem with the treatment system or the pipes which distribute
water, and indicates that the water may be contaminated with germs
that can cause disease.
Fecal Coliform and E coli are bacteria whose presence indicates that
the water may be contaminated with human or animal wastes. Microbes in
these wastes can cause short-term effects, such as diarrhea, cramps,
nausea, headaches, or other symptoms.
Turbidity has no health effects. However, turbidity can interfere with
disinfection and provide a medium for microbial growth. Turbidity may
indicate the presence of disease causing organisms. These organisms
include bacteria, viruses, and parasites that can cause symptoms such
as nausea, cramps, diarrhea, and associated headaches.
Cryptosporidium is a parasite that enters lakes and rivers through
sewage and animal waste. It causes cryptosporidiosis, a mild
gastrointestinal disease. However, the disease can be severe or fatal
for people with severely weakened immune systems. EPA and CDC have
prepared advice for those with severely compromised immune systems who
are concerned about Cryptosporidium.
Giardia lamblia is a parasite that enters lakes and rivers through
sewage and animal waste. It causes gastrointestinal illness (e.g.
diarrhea, vomiting, cramps).
Certain minerals are radioactive and may emit a form of radiation
known as alpha radiation. Some people who drink water containing alpha
emitters in excess of EPA's standard over many years may have an
increased risk of getting cancer.
Beta/photon emitters. Certain minerals are radioactive and may emit
forms of radiation known as photons and beta radiation. Some people
who drink water containing beta and photon emitters in excess of EPA's
standard over many years may have an increased risk of getting cancer.
Combined Radium 226/228. Some people who drink water containing radium
226 or 228 in excess of EPA's standard over many years may have an
increased risk of getting cancer.
Radon gas can dissolve and accumulate in underground water sources,
such as wells, and in the air in your home. Breathing radon can cause
lung cancer. Drinking water containing radon presents a risk of
developing cancer. Radon in air is more dangerous than radon in water.
Technical fact sheets on Inorganic Contaminants
Arsenic. Some people who drink water containing arsenic in excess of
EPA's standard over many years could experience skin damage or
problems with their circulatory system, and may have an increased risk
of getting cancer.
Fluoride. Many communities add fluoride to their drinking water to
promote dental health. Each community makes its own decision about
whether or not to add fluoride. EPA has set an enforceable drinking
water standard for fluoride of 4 mg/L (some people who drink water
containing fluoride in excess of this level over many years could get
bone disease, including pain and tenderness of the bones). EPA has
also set a secondary fluoride standard of 2 mg/L to protect against
dental fluorosis. Dental fluorosis, in its moderate or severe forms,
may result in a brown staining and/or pitting of the permanent teeth.
This problem occurs only in developing teeth, before they erupt from
the gums. Children under nine should not drink water that has more
than 2 mg/L of fluoride.
Lead typically leaches into water from plumbing in older buildings.
Lead pipes and plumbing fittings have been banned since August 1998.
Children and pregnant women are most susceptible to lead health risks.
For advice on avoiding lead, see EPA's lead in your drinking water
Synthetic Organic Contaminants,
including pesticides & herbicides
Di 2-ethylhexyl adipate
Di 2-ethylhexyl phthalate Dibromochloropropane
Heptachlor epoxide Hexachlorobenzene
PCBs [Polychlorinated biphenyls]
Technical fact sheets on Synthetic Organic Contaminants
Volatile Organic Contaminants
Technical fact sheets on Volatile Organic Contaminants
Many water suppliers add a disinfectant to drinking water to kill
germs such as giardia and
e coli. Especially after heavy rainstorms, your water system may add
more disinfectant to guarantee that these germs are killed.
Chlorine. Some people who use drinking water containing chlorine well
in excess of EPA's standard could experience irritating effects to
their eyes and nose. Some people who drink water containing chlorine
well in excess of EPA's standard could experience stomach discomfort.
Chloramine. Some people who use drinking water containing chloramines
well in excess of EPA's standard could experience irritating effects
to their eyes and nose. Some people who drink water containing
chloramines well in excess of EPA's standard could experience stomach
discomfort or anemia.
Chlorine Dioxide. Some infants and young children who drink water
containing chlorine dioxide in excess of EPA's standard could
experience nervous system effects. Similar effects may occur in
fetuses of pregnant women who drink water containing chlorine dioxide
in excess of EPA's standard. Some people may experience anemia.
Disinfection byproducts form when disinfectants added to drinking
water to kill germs react with naturally-occuring organic matter in
Total Trihalomethanes. Some people who drink water containing
trihalomethanes in excess of EPA's standard over many years may
experience problems with their liver, kidneys, or central nervous
systems, and may have an increased risk of getting cancer.
Haloacetic Acids. Some people who drink water containing haloacetic
acids in excess of EPA's standard over many years may have an
increased risk of getting cancer.
Bromate. Some people who drink water containing bromate in excess of
EPA's standard over many years may have an increased risk of getting
Chlorite. Some infants and young children who drink water containing
chlorite in excess of EPA's standard could experience nervous system
effects. Similar effects may occur in fetuses of pregnant women who
drink water containing chlorite in excess of EPA's standard. Some
people may experience anemia.
MTBE is a fuel additive, commonly used in the United States to reduce
carbon monoxide and ozone levels caused by auto emissions. Due to its
widespread use, reports of MTBE detections in the nation's ground and
surface water supplies are increasing. The Office of Water and other
EPA offices are working with a panel of leading experts to focus on
issues posed by the continued use of MTBE and other oxygenates in
gasoline. EPA is currently studying the implications of setting a
drinking water standard for MTBE.
Health advisories provide additional information on certain
contaminants. Health advisories are guidance values based on health
effects other than cancer. These values are set for different
durations of exposure (e.g., one-day, ten-day, longer-term, and
Measure and adjust pool water to the following levels
1) pH to 7.2-7.6
2) Total Alkalinity to 80-150 ppm
3) Calcium Hardness 200-400 ppm for concrete or 175-225 ppm for vinyl
4) Free Chlorine to 1-3 ppm