A chemical that contains hydrogen and can dissolve metals, reacts with
bases to form salts, and neutralizes alkaline materials.
The amount of acid needed to lower pH to the proper level for pool
Microscopic plants deposited in pool or spa water by wind, rain, and
Natural or synthetic substance used for killing, destroying, or
A condition where the pH of water is above 7.0 on the pH scale.
Alkaline (often referred to as "base") is the opposite of acidic.
Reversing the flow of water through the filter to clean the elements
of the filter.
Microscopic organisms which may be living in the pool water, many of
which can cause infection or disease.
A chemical of an alkaline nature that reacts with acids to form salts
and neutralizes acidic materials.
The amount of base (or pH increaser) water needs to reach the proper
A type of algae that grows on pool walls and floors as dark spots.
Colonies usually form in areas with less circulation. Black algae
feels slimy and can be brushed off with some effort. The algae imbeds
itself into porous pool surfaces and can be difficult to completely
A chemical that works to prevent fluctuations in pH.
Scale that forms on pool surfaces from calcium compounds when pool
water is too alkaline, calcium hardness is too high, or total
alkalinity is too high.
The amount of calcium dissolved in water expressed in ppm (parts per
A chlorine compound using calcium as the carrying salt for
A chemical compound that ties up iron, copper, or calcium to prevent
staining and scaling. Also called a sequestering agent.
Substances formed when chlorine combines with swimmer wastes (nitrogen
or ammonia), causing chlorine odor and irritation to skin and eyes.
The most widely used bacteria-killing agent for recreational water
treatment. In its elemental form it is a gas and stored in cylinders.
Various chlorine compounds are available for pool sanitation,
including calcium hypochlorite and chlorinated isocyanurates.
The chlorine needed to establish a stable, residual chlorine amount
for proper sanitation.
The amount of chlorine readily available after the chlorine demand has
been satisfied or not bound up in chloramines.
A product that causes fine suspended particles in water to combine
into filterable or vacuumable clusters.
Chlorine that is chemically bonded to other compounds.
The effect of an acidic environment where pH and/or alkalinity are
A chemical compound added to pool water to reduce the degradation of
chlorine by the ultraviolet rays of the sun.
Diatomaceous Earth (DE):
A powdery filtering agent composed of the skeletal remains of diatoms
(a form of plankton) used in DE filters.
Dichlor (sodium dichloro-s-triazinetrione):
A fast-dissolving chlorine compound with a neutral pH.
The reagent that measures free available chlorine.
Sand, DE, or other material used to filter particles out of the water.
A chemical compound added to water causing suspended particles to bond
together and sink to the bottom of the pool where they can be
Free Available Chlorine:
Chlorine in pool water that is not combined with ammonia or
nitrogenous compounds and is available to sanitize the water.
A free-floating organism that turns water cloudy and green. This type
of algae is the most common and easiest to clear up.
The amount of calcium and magnesium dissolved in water. It is measured
in ppm (parts per million).
An inorganic (unstabilized) family of chlorine compounds used in
various forms to provide chlorine for water treatment. Includes
calcium hypochlorite and sodium hypochlorite.
The free state of chlorine that actually destroys bacteria and other
Unstabilized chlorine that is vulnerable to degradation by the
ultraviolet rays of the sun.
A metal often present in fill water that can make water greenish,
yellow, or rust-colored.
The process where improperly balanced pool water can extract minerals
from pool surfaces and plaster interiors.
Sodium hypochlorite solution used as a disinfectant.
The metals that may be present in water include iron and copper. When
either is dissolved in water, the addition of a shock product can turn
the water various colors and/or stain the surfaces.
Calcium, manganese, magnesium, nickel, copper, silver, iron, cobalt,
and aluminum may be present in water. In high, non-chelated
concentrations, minerals can lead to stains and scale.
See Yellow Algae.
A class of chemical compounds used to oxidize or shock the water
without chlorine or bromine.
A form of chlorine that contains the compound triazinetrione. The most
common forms of organic chlorine are dichlor (sodium
dichloro-s-triazinetrione) and trichlor (trichloro-s-triazinetrione).
A product that destroys organic and inorganic contaminants such as
ammonia, chloramines, and swimmer waste.
A measurement that indicates the acidic or basic nature of the pool
water. The pH scale runs from 0 to 14. 7.0 is neutral, a pH below 7.0
is acidic, and a pH above 7.0 is basic. The acceptable range is
between 7.2 and 7.8.
Not actually an alga, but bacteria that forms colonies with a slimy
Parts Per Million, a unit of measurement that indicates the amount, by
weight, of a chemical in relation to one million parts by weight of
Quaternary ammonium algaecides, which are compounds added to water to
prevent or kill the growth of algae.
Chemical testing compounds that are used to test for chlorine,
bromine, pH, total alkalinity, calcium hardness, etc.
The amount of bromine or free available chlorine remaining in the
A chemical agent used to destroy unwanted microorganisms in water.
Mineral deposits that form on pool surfaces and equipment due to
excessive calcium in the water.
A product that ties up minerals tightly in solution, preventing their
precipitation, which otherwise forms scale, colors the water, or
stains surfaces. Also called a chelating agent.
Adding an oxidizing compound to pool or spa water to chemically break
up (oxidize) contaminants like oils, perspiration, and dirt that can
interfere with pool sanitation.
A powder added to water to increase pH. Also known as soda ash.
A powder added to water to increase the total alkalinity.
An organic compound of chlorine and cyanuric acid. The most common
types are dichlor (sodium dichloro-s-triazinetrione) and trichlor
A collection of liquid and/or tablet reagents assembled for the
purpose of measuring a range of water quality parameters.
>Total Alkalinity (TA):
The amount of alkaline substances present in water. Low total
alkalinity can cause metal corrosion, plaster etching, and eye
irritation. High total alkalinity causes scale formation, poor
chlorine efficiency, and eye irritation.
The sum of both the free and combined chlorine residuals in water.
The combined amount of calcium and magnesium hardness in pool water.
Trichlor (Trichloro-s-Triazinetrione): A slow-dissolving, organic
compound containing 90% available chlorine, typically compressed into
sticks and tablets.
A microorganism that appears on pool walls as a fine dust. Typically
it is seen first on surfaces that don't receive direct sunlight. This
algae is easy to brush off, but it frequently returns. Also called