Acid
A chemical that provides hydrogen ions(H+). An acid lowers the pH of water

Acid Demand Reagent (ADR)
A reagent used in association with the pH test to determine the amount of pH decreaser (e.g., muriatic acid, carbon dioxide or sodium bisulfate) required to accomplish the desired pH reduction.

Algae
The simplest members of the plant kingdom. Algae are microscopic, single-celled forms of plant life that exist in virtually all surface water and most ground water. Green, black, and mustard are the most frequently encountered species in pools and spas.

Available Chlorine Content (ACC)
An index to permit easy comparison of available chlorine present in different halogenated compounds.

Base Demand Reagent (BDR)
A reagent used in association with the pH test to determine the amount of pH increaser (e.g., sodium carbonate or sodium hydroxide) required to accomplish the desired pH increase.

Breakpoint Chlorination
The process of adding sufficient free available chlorine (FAC) or other oxidant (i.e., persulfate) to chemically convert chloramines and ammonia-nitrogen compounds to inert nitrogen gas (N2).

Bromamines
The by-product formed when free hypobromous acid (HOBr) reacts with ammonia and nitrogenous compounds. Unlike chloramines, bromamines are excellent disinfectants and algaecides.

Bromine
An element of the halogen family. Bromine compounds are used as disinfectants added to swimming pool or spa water. They destroy and inhibit bacteria and algae growth in addition to oxidizing unwanted organic and nitrogenous compounds.

Buffer
Mixtures of weak acids and their salts or of weak bases and their salts. For example, sodium bicarbonate is an excellent buffer. Buffers resist a change in pH upon the addition of small amounts of acids or bases.

Calcium Hardness
The calcium content of water expressed in milligrams per liter or ppm.

Calcium Hypochlorite
Available as a dry, free-flowing granular or pellet, this inorganic chlorinating compound normally has an active strength and available chlorine content of 65%.

Chlorine
An element of the halogen family. Chlorine compounds are used as a disinfectant added to swimming pool or spa water. They destroy and inhibit bacteria and algae growth in addition to oxidizing unwanted organic and nitrogenous compounds.

Chlorine Demand
The difference between the amount of free available chlorine applied and the amount of free, combined or total available chlorine remaining at the end of the contact period. Chlorine demand is caused by inorganic minerals such as ferrous iron (Fe2+), manganese (Mn2+), ammonia, amino acids, etc.

Coagulation
The process of gathering together smaller particles to form a mass or group large enough to be effectively filtered. Poly-A provides superior coagulation in the Vantage Program.

Combined Available Chlorine (CAC)
Known also as chloramines, CAC are the undesirable compounds formed when
insufficient levels of free available chlorine chemically react with ammonia and other nitrogenous compounds.

Dehalogenation
The addition of halogen-neutralizing compounds to rapidly destroy excess halogen.
This process is not recommended for a pool sanitized with brominating products.

Diatomic
Consisting of two atoms; having two atoms in a molecule such as diatomic fluorine (F2), diatomic oxygen (O2), etc.

Disinfection
The process of destroying and/or inhibiting the growth of bacteria and viruses so as to prevent the transmission of disease.

DPD
A color indicator used for the determination of the residual present in the water of chlorine, bromine, ozone, and other reactive oxidizers. DPD is chemically N,N-diethyl-p-phenylenediamine.

Filter Septum
The individual dividing members of a Diatomaceous Earth (D.E.) filter.

Filtration
The passage of a fluid through a porous medium to remove matter (particles)
held in suspension.

Flocculation
The formation of tiny, individual particles into a larger mass that settles to the bottom of the pool for easy removal.

Flow meter
A metering device that measures flow rate in gallons per minute or liters per minute.

Flow Rate
The rate of flow through a recirculation system usually expressed in gallons per minute or liters per minute.

Fluorine: The most highly electronegative element known. Its principle source is fluorite or fluorspar (CaFl2).

Free Available Chlorine (FAC)
The desirable form of chlorine for disinfection. FAC is the portion of the chlorine residual which is not combined with ammonia and other nitrogenous compounds to form chloramines. Half-Life: The time required for half of something to undergo a process, such as the time required for a 1 ppm of ozone to decompose to 0.5 ppm ozone.

Halogen
Any element found in Group VII A of the Periodic Table. The halogens include fluorine, chlorine, bromine, iodine, and astatine. Because of their tremendous chemical reactivity, the halogens never occur free in nature.

Hydrogen Peroxide
A thermally unstable, active oxidizing agent (H2O2). When used as an oxidizing agent, its only by-product of the oxidizing reactions is water (H2O).

Hypobromous Acid (HOBr)
The by-product produced when elemental bromine or other brominating compounds react with water. Hypobromous acid is the active acid form of the bromine disinfectant responsible for disinfection and oxidation. Bromamines are also active disinfectants in brominated pools and spas.

Hypochlorous Acid
The by-product produced when elemental chlorine or other chlorinating compounds react with water.Hypochlorous acid (HOCl) is the active disinfecting species found in chlorinated pools and spas.

Ionization
The natural or artificially induced electrochemical process of converting electrically neutral (non-charged) atoms, molecules or compounds to electrically charged ions.

Lithium Hypochlorite
A dry, granular chlorinating compound (LiOCl) with an active strength of 29% and an available chlorine content of 35%.

Micron
A unit of measure equal to 1/1000 of a millimeter.

Muriatic Acid
A strong mineral acid composed of one atom of hydrogen and one atom of chlorine (HCl). Scientifically known as hydrochloric acid or hydrogen chloride.

OTO
A color indicator for measuring the residual of total available chlorine and bromine. Also known as orthotolidine, OTO is frequently used in simple test kits for poolside chlorine residual determination.

Oxidation
The process of changing a compound or molecule from a lower to a higher positive oxidation state. For example, the carbon atom of undesirable organic compounds is oxidized to carbon dioxide (CO2). The carbon atom of carbon dioxide has a higher positive oxidation state.

Oxidation Reduction Potential (ORP)
The potential of a chemical reaction, measured in millivolts (mv), where one or more electrons are transferred from one atom or molecule to another.

Oxidizing Agent
Compounds that are characterized by their tendency to gain electrons from other atoms, encouraging the oxidation (loss of electrons) of other compounds. For example, hypochlorous acid (HOCl) gains two electrons when it oxidizes manganous ion (Mn2+) to manganese dioxide (MnO2). Manganous ion loses two electrons.

Ozone
A triatomic form of oxygen (O3) that is a bluish irritating gas of pungent odor. Although ozone is naturally produced in the upper atmosphere, ozone can be artificially produced and used in disinfection, deodorization, oxidation and bleaching.

pH
Mathematically defined as the negative log of the hydrogen ion concentration
(pH = –LOG[H+]), pH is a measure of the acidity or basicity of water.

Phenol Red
Chemically known as phenolsulfonthalein. Phenol red is an organic acid-base indicator that exhibits a yellow to red color change as the pH increases from 6.8 to 8.2.

Physiochemical
Being of both physical and chemical components.

Polymeric Flocculent
Water soluble, very large molecule which promotes flocculation to aid in removal of solids.

Reducing Agent
The opposite of oxidizing agent. Reducing agents give up electrons to other atoms. For example, sodium sulfite (Na2SO3) gives up two electrons when reducing (neutralizing) hypochlorous (HOCl) or hypobromous acid (HOBr).

Sanitation
The removal or neutralization of elements harmful to health through a combination of disinfection and oxidation. Following EPA-approved application instructions, HOBr and HOCl are equivalent sanitizers.

Sequestrant
A molecule or compound that chemically reacts with potential stain-producing minerals (e.g., iron, copper, manganese, etc.) and calcium. This reaction protects the pool/spa surface and equipment from unsightly stain or scale formations.

Sodium Bisulfate (NaHSO4)
A dry, crystalline-like acid with hygroscopic (water-absorbing) properties.

Sodium Dichlor
A key member of the chlorinated cyanurate family. Each molecule of sodium dichlor has two available chlorine atoms with an available chlorine content of 62%.

Sodium Hydroxide
Frequently called caustic soda, sodium hydroxide contains one atom each of sodium, hydrogen and oxygen (NaOH). It yields strongly basic solutions with pH exceeding 13.

Sodium Hypochlorite
A liquid chlorinating compound (NaOCl) containing approximately 10% to 12% available chlorine content.

Soft Water
Water that has a low or insignificant dissolved calcium and magnesium content.

Stabilization
The process of adding cyanuric acid (chemically known as s-triazine trione) to protect outdoor pools and spas from UV degradation of active chlorine residuals. A brominated system does not require the use of cyanuric acid.

Sterilization
The complete (100%) destruction of all living organisms.

Total Alkalinity (TA)
The quantitative measurement of the alkaline components present in water to act as a buffer against rapid pH changes. For the most part, total alkalinity is a combination of carbonate, bicarbonate and hydroxide.

Total Available Chlorine (TAC)
The sum of the residuals of free available chlorine (FAC) and combined available chlorine (CAC).

Transition Metals
The fourth period of the Periodic Table containing the following elements: scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel and copper.

Triatomic
Consisting of three atoms; having three atoms in a molecule such as triatomic oxygen (O3). Ozone is a triatomic oxygen molecule.

Trichlor
A primary member of the chlorinated cyanurate family containing three available chlorine atoms. Trichlor is usually found with an available chlorine content of 90%.