Commonly Used Water Terms G - L
Welcome to the Water Guy list of commonly used water terms. Navigate the page
sections below:
GPG
Abbreviation for grains per gallon.
GRAIN
(gr.) A unit of weight equal to 1/ 7000th of a pound. or 0.0648 gram.
GRAIN PER GALLON
(gpg) A common basis for reporting water analyses in the United States and
Canada; one grain per U.S. gallon equals 17.12 milligrams per liter (mg/I) or
parts per million (ppm). One grain per British (Imperial) gallon equals 14.3
milligrams per liter or parts per million.
GRAM
(g) The basic unit of weight (mass) of the metric system, originally intended to
be the weight of one cubic centimeter of water at 4?C.
GREENSAND
A natural mineral. primarily composed of complex silicates, which possesses ion
exchange properties.
HARDNESS
A characteristic of natural water due to the presence of dissolved calcium and
magnesium; water hardness is responsible for most scale formation in pipes and
water heaters, and forms insoluble "curd" when it reacts with soaps. Hardness is
usually expressed in grains per gallon, parts per million. or milligrams per
liter. all as calcium carbonate equivalent.
HARDNESS LEAKAGE
The presence of a consistent concentration of hardness in the effluent from an
ion exchange water softener, often due to high concentrations of hardness or
sodium in the water being treated (see Leakage)..
HARD WATER
Water with a total hardness of one grain per gallon or more, as calcium
carbonate equivalent.
HEAD
A measure of the pressure at a point in a water system; expressed in pounds per
square or in the height of a column of water which would produce the pressure.
HEAD LOSS
See Pressure Drop.
HYDRAULIC
Referring to water or other fluids in motion.
HYDRAULIC CLASSIFICATION
A process in which particles of the same specific gravity may be graded
according to size by backwashing or other relative upward flow of water; the
smallest particles tending to rise to the top of the bed, and the largest
particles tending to sink to the bottom, due to variations in weight to surface
area ratios.
HYDROGENCYCLE
The cation exchange cycle in which the cation exchanger is regenerated with
acid, and cations are removed from the solution treated in exchange for hydrogen
ions.
HYDROGEN ION CONCENTRATION
The concentration of hydrogen ions in moles per liter of solution; often
expressed as pH (see pH).
HYDROLOGIC CYCLE
The water cycle, including precipitation of water from the atmosphere as rain or
snow, flow of water over or through the earth, and evaporation or transpiration
to water vapor in the atmosphere. (see Transpiration)
HYDROLYSIS
The reaction of a salt with water to form an acid and a base.
HYDROXIDE
A chemical compound of an element or elements with the hydroxyl (OH) anion. (See
Hydroxyl)
HYDROXYL
The chemical group or ion (OH) which is neutral or positively charged.
HYPOCHLORITE
The "OCI" anion; calcium and sodium hypochlorites are commonly used as bleaches
and disinfecting agents.
ION
An atom or group of atoms which functions as a unit. and has a positive or
negative electrical charge, due to the gain or loss of one or more electrons.
(see Ionization)
ION EXCHANGE
A reversible process in which ions are released from an insoluble permanent
material in exchange for other ions in a surrounding solution; the direction of
the exchange depends upon the affinities of the ion exchanger for the ions
present. and the concentrations of the ions in the solution. (see Base Exchange)
ION EXCHANGER
A permanent, insoluble material which contains ions that will exchange
reversibly with other ions in a surrounding solution. Both cation and anion
exchangers are used in water conditioning.
IONIZATION
The process in which atoms gain or lose electrons and thus become ions with
positive or negative charges; sometimes used as a synonym for dissociation, the
separation of molecules into charged ions in solution. .
IONIZATION CONSTANT
A constant, specific for ~ach partially ionizable chemical compound, to express
the ratio of the concentration of ions from the compound to the concentration of
un-ionized compound.
IRON
An element often found dissolved in ground water (in the form of ferrous iron)
in concentrations usually ranging from zero to 10 ppm (mg/I). It is
objectionable in water supplies because of the staining caused after oxidation
and precipitation (as ferric hydroxide); because of tastes; and because of
unsightly colors produced when iron reacts with tannins in beverages such as
coffee and tea.
IRON BACTERIA
Organisms which are capable of utilizing ferrous iron (either from the water or
from steel pipe) in their metabolism and precipitating both ferric hydroxide in
their sheaths and gelatinous deposits. These organisms tend to collect in pipe
lines and tanks during periods of low flow, and to break loose in slugs of
turbid water to create staining, taste, and odor problems.
JACKSON TURBIDITY UNIT (JTU)
A quantitative unit of turbidity originally based on the comparison of a liquid
(such as water) with a suspension of a specific type of silica, using the
turbidity measure in a Jackson Candle Turbidimeter.
KILO
A prefix used to indicate 1000 of the succeeding unit. (Kilo is also sometimes
used as an abbreviation for kilogram.)
KILOGRAIN (Kgr)
One thousand grains.
KILOGRAM (Kg)
One thousand grams.
LANGELIER'S INDEX
A calculated number used to predict whether or not a water will precipitate, be
in equilibrium with, or dissolve calcium carbonate. It is sometimes erroneously
assumed that any water which tends to dissolve calcium carbonate is
automatically corrosive.
LEAKAGE
The amount of contaminant or hardness remaining in water after filtering or
other treatment.
LIME
The common name for calcium oxide (CaO); hydrated lime is calcium hydroxide
[Ca(OH)2).
LIME SCALE
Hard water scale containing a high percentage of calcium carbonate.
LIMESTONE
A sedimentary rock, largely calcium carbonate, usually also containing
significant amounts of magnesium carbonate.
LITER
The basic metric unit of volume; 3. 785 liters equals one U.S. gallon. One liter
of water weighs 1000 grams.
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