Natare Terminology

Chemical Treatment

a b c d e f g h i j k l m n o p q r s t u v w x y z


  • ACID

    a sour chemical substance containing hydrogen with the ability to dissolve metals, neutralize alkaline materials and combine with bases to form salts; acid is used to lower (decrease) pH and total alkalinity of swimming pool and spa water; examples are muriatic acid (hydrochloric) and dry acid (sodium bisulfate)

  • Acid DEMAND

    amount of acid needed to lower pH to the proper level for pool water


    reagent test usually used in conjunction with a pH test to determine the amount of acid needed to lower pH and total alkalinity levels


    precipitation having an unusually low pH value (4.5 or lower) caused by absorption of air polluted by sulfur dioxide, carbon dioxide and nitrous oxide


    1. to kill algae; algaecides perform best as a backup to a routine sanitation program
    2. help to kill airborne spores as they blow into the pool

    retards and prevents algae genesis and growth

  • Algae

    1. microscopic plants deposited in pool or spa water by wind, rain and dust, they thrive in sunlight and warm water, clogging pool equipment and causing slippery surfaces and green water; there are 21,000 known species of algae
    2. algae are not disease causing, but can harbor bacteria, and it is slippery
    3. most common pool types are black, blue-green, green and mustard (yellow or drawn)
    4. pink or red-colored algae-like organisms exist but are bacteria and not algae; maintaining proper sanitizer levels, shocking and superchlorination will help prevent algae occurrence

    1. basic chemical that neutralizes acids by releasing carbonates and/or hydroxides
    2. also called base
    3. the opposite of acid
  • Alkaline

    when pool water measures above 7.0 on the pH scale

  • Alkalinity

    1. amount of carbonate, bicarbonate and hydroxide compounds in pool water
    2. more commonly called total alkalinity
    3. measure of the pH-buffering capacity of water
    4. also called the water’s resistance to change in pH
    5. one of the basic water tests necessary to determine water balance
  • Alum

  • Ammonia (NH3)

    1. nitrogen-containing compound that combines with free chlorine to form chloramines; chloramines have a strong chlorine odor and can cause skin and eye irritation
    2. introduced into the water by swimmers as waste (perspiration or urine) or by other means; quickly forms foul-smelling, body-irritating chloramine – a disabled, less- effective form of chlorine

    chemical added to the water to make the sud or foam disappears; these products do not remove the source of the sudsing; most often, the water must be drained and refilled to remove the soaps, oils and other causes of foaming; shocking and superchlorination may help prevent foaming


    see free available chlorine

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    1. condition caused by too much copper not chlorine in the pool water; the copper may get into the water by the bad practice of placing trichlor tabs in the skimmer; this acidic product will cause low-pH water, which will in turn dissolve metals in the equipment; the dissolved metal (usually copper) then stains hair, fingernails and, eventually, pool walls
    2. can also be caused by keeping the pH too low or misusing acid

    1. arrangement of pipes, gates and valves by which the flow of water may be passed around a piece of equipment or diverted to another piece of equipment
    2. a controlled diversion


    1. substance or compound that stabilizes the pH value of a solution
    2. water’s resistance to change in pH
  • Bromine (BR2)

    1. chemical used in various compound forms to sanitize pool and spa water
    2. it forms hypobromus acid in water
    3. available as a tablet or as sodium bromide, a granular salt
    4. member of the halogen family
    5. used as a sanitizer in spas, because of its resistance to hot water with rapid pH fluctuations

    mechanical or electrical device for dispensing bromine at a controlled rate; most often a canister or floater filled with tablets of bromine


    1. a common term for a bromide salt used to supply bromide ions to the water so they may be oxidized or changed into hypobromous acid, the killing form of bromine
    2. used as a disinfectant

    1. by-products formed when bromine reacts with swimmer waste, nitrogen or fertilizer
    2. active disinfectants that do not smell although high levels are body irritants
    3. removed by superchlorination or shock treating
    4. a combined bromine-ammonia molecule; unlike chloramines, which are strong smelling and offer no sanitizing properties, bromamine compounds continue to sanitize
  • Breakpoint Chlorination

    process of adding sufficient free available chlorine to completely oxidize all organic matter and ammonia or nitrogen compounds; all chlorine added after that point is free available chlorine


  • Biguanide


    see acid demand

  • BASE

    see alkali

  • Balanced Water


    1. sodium bicarbonate
    2. white powder used to raise the total alkalinity of pool or spa water without having much affect on pH

    kills bacteria; chlorine is a bactericide and germicide; silver "algaecides" are actually more bactericide, and are useful on pink "algae"


    single-celled microorganisms of various forms, some of which are undesirable or potentially disease-causing; bacteria are controlled by chlorine, bromine or other sanitizing and disinfecting agents

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    1. a granular chemical added to the pool water, which provides a shield to chlorine for protection from UV radiation, which disrupts the molecule, destroying its sanitizing ability
    2. also called stabilizer conditioner

    see clarifier


    see chlorine combined


    any microparticle or organism, which reduces water clarity or quality, or presents health hazards


    effective algaestat and algaecide, copper as elemental is used in many pool products


    chemical compound that contains the element copper; too much copper in the water can cause green-colored stains; newer copper algaecides contain an ingredient that prevents the copper from staining but does not affect copper’s ability to kill algae; these special copper algaecides are called chelated copper algaecides


    similar to aluminum sulfate, this chemical provides a coagulating and flocculent function in water; used in ponds; this amount of copper would stain swimming pools

  • Conditioned Water


    see cyanuric acid

  • Corrosion


    quantity of free available chlorine removed during the process of sanitizing; the amount of organic and non-organic material contained in the water will "demand" a certain level of oxidizer to be destroyed


    1. also called coagulant or flocculant
    2. chemical compound used to gather (coagulate or agglomerate), or to precipitate suspended particles so they may be removed by vacuuming or filtration; there are two types

    see residual chlorine

  • chlorine NEUTRALIZER

    1. chemical used to make chlorine harmless; used in test kits to counteract the bleaching effect of the chlorine or bromine in order to increase the accuracy of pool water tests
    2. sold as chlorine and bromine neutralizer, it is used to destroy excessive amounts of chlorine or bromine, so the high levels will not affect swimmers

    term that implies that an over abundance of cyanuric acid (stabilizer or conditioner) in the water would cause the chlorine to be all "locked up;" this is not true


    electrical device that generates chlorine from a salt solution in a tank or from salt added to the pool water


    chemical compound that when used in conjunction with chlorine makes the chlorine perform better as an algaecide

  • CHLORINE total available

    sum of combined and free chlorine levels; with a DPD test kit, one determines free available level, then total available; the difference, if any, is the level of combined chlorine


    primary in the make up of total alkalinity and total dissolved solids


    1. naturally occurring polymer found in the shells of crabs and lobsters
    2. contained in the some proprietary pool products, chitin acts as a coagulant and flocculent for oils, metals and organic materials

    (pronounced KEY-late)

    1. process of preventing metals in the water from combining with other components in water to form colored precipitates that stain the pool walls and bottom or produce colored water
    2. also called a sequestering agent

    algaecides that contain a special ingredient to prevent the copper from staining the pool walls and bottom or producing colored water


    similar to sequestering agents, a chelating agent is a water soluble molecule that can bond tightly with metal ions, keeping them from coming out of suspension and depositing their stains and scale onto pool surfaces and equipment

  • Chemical Feeder

  • Chloramines


    see isocyanurate


    mechanical or electrical device for dispensing chlorine at a controlled rate; most often a canister or floater filled with tablets of chlorine

  • Chlorine (Cl2)

    1. most widely used bacteria-killing agent for pool water; organic chlorine is more suitable than inorganic for pool use because it is generally easier to use, does not affect water balance as much and is non-clouding
    2. oxidizes ammonia and nitrogen compounds (swimmer and bather waste)
    3. member of the halogen family of sanitizers, its use in swimming pools is in the elemental form of a gas, or as a liquid, granular or tablet compound

    see free available chlorine

  • CHLORINE combined

    1. portion of total available chlorine left over when free available is subtracted
    2. measure of chlorine that has already combined with other molecules or organisms, primarily chloramines

    crystalline compounds formed in swimming pool and spa water when the calcium, pH and total alkalinity levels are too high; once formed, the crystals adhere to the plumbing, equipment, pool walls and bottom; these crystals are better known as scale

  • Calcium Hypochlorite CA(OCL2)

    see hypochlorite

  • Calcium Hardness

  • Calcium Chloride (CaCl2)

    1. soluble salt added to pool water to raise the calcium hardness level
    2. commonly used for snow melting
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    see anti-foam


    1. common name for sodium dichlor
    2. fast dissolving chlorine compound containing chlorine and cyanuric acid (stabilizer or conditioner); it has a neutral pH and is quick-dissolving, so it can be used for regular chlorination or superchlorination

    see overdrain


    to kill all pathogenic (disease-causing) organisms


    chemicals or processes, which work to destroy vegetative forms of microorganisms and other contaminants; examples are chlorine, bromine, Soft-Swim, ionizers and copper and silver algaecides


    demand that your pool has for dirt; this level is invertedly proportional to available time for cleaning; if you remove the dirt from the pool, you have created a dirt deficit, and the pool will actually suck dirt out of the air to maintain its dirt demand


    see overdrain

  • DPD (Diethyl-P-Phenylene Diamine)

    a test reagent used to measure the amount of available chlorine in pool water; measures both total and free chlorine

  • Dry Acid

    1. sodium bisulfate
    2. lowers pH and total alkalinity to proper levels
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    1. electrochemical reaction causing a black stain normally found around metal fixtures or on the plaster; caused by two dissimilar metals being plumbed together or from an improper electrical grounding of pool equipment or lights
    2. decomposition of water and other inorganic compounds in aqueous solution by means of electricity; chlorine generators use this principle to produce chlorine from salt in the water

    designed to break down and digest oils


    1. power to produce an effect
    2. chlorine’s efficacy is affected by many factors, including the sun, water balance and the water’s chlorine demand
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    used in filling or adding to the water level

  • FILM-X

    1. compound of citric acid used in cleaning plaster and other pool areas
    2. safe replacement for muriatic acid

    surface foam on water caused by high TDS levels

  • FLOC

    clump or tuft formed when suspended particles combine with a flocculating agent


    see clarifier


    combination, agglomeration, aggregation or coagulation of suspended particles in such a way that they form small clumps or tufts (called floc)

  • Flocculating Agent

    see clarifier

  • FOAM

    froth of bubbles on the surface of the water; usually from soap, oil, deodorant, hair spray, suntan oil, etc., that is shed into the water as swimmers enter

  • FREE Available CHLORINE

    1. free chlorine in the pool or spa water that is available to sanitize or disinfect the water
    2. hypochlorous acid, the chlorine in pool water that is not combined with ammonia or nitrogen and therefore available to kill bacteria entering the pool
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  • Hypochlorous ACID (HOCI)

    active sanitizing form of chlorine

  • Hypobromous Acid (HOBr)

    most effective form of bromine in water for disinfecting

  • Hypochlorinator

    feeder device that applies chlorine solutions to pool water at a controlled rate

  • Hypochlorite

    inorganic un-stabilized family of chlorine compounds used in various forms to provide chlorine for pool water; includes calcium hypochlorite, lithium hypochlorite and sodium hypochlorite


    chemical elements either individually or collectively that constitute Group VIIB of the Periodic Table of Elements


    1. water that is high in calcium hardness and other salts
    2. resists soap being lathered

    1. amount of calcium and magnesium dissolved in the water
    2. "water" or "total" hardness refers to the total magnesium and calcium dissolved in the water; calcium hardness refers to just the calcium
    3. measured by a test kit and expressed as ppm; proper range is 200 to 400 ppm

    chemical compound used to kill or control plant growth or algae

  • Hydrochloric Acid (HCI)

    1. strong acid used to control pH in pools and to acid wash pool interiors
    2. also called muriatic acid

    1. lightest chemical element
    2. component of water
    3. frequent product of many chemical reactions; pH is a measure of hydrogen in its ionic form in water
  • Hydrogen Ion

    positively charged nucleus of a hydrogen atom, which contributes to the acidity of pool water


    unstable, colorless, heavy liquid used as an oxidizing agent in pools and spas; may also be used to dechlorinate pool or spa water

  • Hydroxyl Ion (OH-)

    1. negatively charged particle of one oxygen and one hydrogen atom also called hydroxide
    2. contributes to pH balance
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    water-sanitation device that uses electricity to generate metal ions, which are dispersed in the water; it works by passing a low-voltage DC current through a set of metallic (usually copper and silver) electrodes placed in line with the circulation equipment; copper is an algaecide, while silver is a bactericide; does not remove swimmer waste

  • IRON

    usually introduced into the water from iron plumbing or from well water, ferric iron can stain surfaces, while ferrous iron will turn your water a clear green color


    1. also called stabilized chlorine and chlorinated
    2. family of chlorine pool sanitizers that contain conditioner (cyanuric acid or isocyanuris acid) to protect the chlorine from the degrading UV rays in sunlight; the most common types are sodium dichlor and trichlor; the granular form is dichlor, which is fast dissolving and can be used for regular chlorination or superchlorination by broad casing into the pool or spa; tablet or stick form is trichlot (which is usually used in a chlorine feeder – either the floating type or the in-line erosion type) used for regular chlorination only
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    see saturation index

  • Liquid Acid

    see muriatic acid

  • Liquid Chlorine

    1. sodium hypochlorite (NaOCI) solutions
    2. pool disinfectant

    1. dry, granular chlorinating compound with an available chlorine content of 35 percent;
    2. rapid-dissolving
    3. used to superchlorinate vinyl-liner pools, painted pools or fiberglass pools as well as spas and hot tubs
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    1. measure of the amount of magnesium dissolved in the water; part of total or water hardness
    2. causes scale if levels are too high

    any substance that is neither animal nor vegetable; such as calcium, manganese, magnesium, nickel, copper, silver, iron, cobalt or aluminum; their presence in high non-chelated concentrations can lead to stains and scale when conditions are right


    tiny, living, breathing creature in your pool; the purpose of disinfectants is to remove such pathogenic (disease causing) organisms


    the liquid dilution of hydrochloric acid used to lower pH and alkalinity, and to remove mineral stains and scale; extremely caustic and corrosive

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    single oxygen atom, not yet bonded to anything; extremely powerful oxidizer when harnessed


    chemical used to make chlorine or bromine harmless


    gas that causes algae to bloom and disables chlorine


    1. class of chemical compounds used to oxidize or shock the water (destroy ammonia, nitrogen and swimmer waste); they contain no chlorine or bromine and do not kill living organisms; swimmers may re-enter the water in only 15 minutes after adding a non-chlorine shock
    2. granular form of potassium permonosulfate, used to oxidize materials such as microorganisms, contaminants or chloramines
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  • Orthotolidine (OTO)

    see DPD


    incorrect term used to describe water that is acidic or water that has a pH lower than 7.2


    1. also called a diffuser or distributor
    2. internal sand filter device that evenly distributes influent pool water over the sand filter bed
  • Oxidation

    1. chemical process for removing irritating organic compounds from pool water;
    2. rusting or corrosion process that occurs as metals weathers
  • Oxidizers

    agent that helps eliminate organic waste from pool water


    gaseous molecule comprised of three atoms of oxygen; it is generated on-site from air or oxygen and used for oxidation of water contaminants


    molecule containing three atoms of oxygen; known to be a very powerful sanitizer; ozone producing equipment creates this molecule by UV radiation or corona discharge generators

  • Organic Chlorine

    1. form of chlorine that contains carbon and hydrogen atoms
    2. most common ones for pool use are sodium dichloroisocyanurate (also know as sodium dichlorostriazinetrione) in granular form and trichloroisocyanurate (also known as trichlorostriazinetrione) in compressed form
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  • pH

    indicates the acidity or alkalinity of pool water; on a scale of 0 to 14, values below 7 are acidic, while values above 7 are alkaline; ideal pool pH is a reading of 7.4 – 7.6


    chemical reagent dye used to test for pH; it can measure pH from 6.8 to 8.4


    see non-chlorine shock


    1. substance made of giant molecules formed by the union of simpler molecules; many water clarifiers are made from organic polymers; an example would be polymerized ethylene, called polyethylene
    2. algaecide/algaestat made up of repeating polymer molecules; used for green algae and available in varying strengths
  • POTASSIUM Peroxymonosulfate

    1. active ingredient and chemical name of a non-chlorine shock treatment or non-chlorine oxidizer
    2. does not kill bacteria or algae, but it will oxidize or destroy ammonia, nitrogen and swimmer waste;
    3. it has a low pH
    4. does not increase chlorine or bromine levels the way that superchlorination does
    5. reactivates bromine to its killing form, hypobromous acid
  • ppm

    1. parts per million
    2. unit of measurement used in chemical application; it indicates the amount, by weight of a chemical, in relation to one million parts by weight of water (examples
  • Precipitate

    solid particles forced out of solution by a chemical reaction; they may settle to the bottom of the pool or remain suspended in the water

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    chemical compounds of ammonia used as algaecide and algaestats


    see quaternary ammonium compound

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    1. amount of measurable chlorine remaining after treating the water with chlorine
    2. amount of chlorine left in the pool or spa water after the chlorine demand has been satisfied

    condition preventing full flow of water; restriction on the suction side creates higher vacuum, (or suction) while on the pressure side creates higher pressure


    chemical agents, dyes, indicators or titrants used in testing water balance


    1. reinforcement bar
    2. used to add strength to a concrete; after excavation of an in ground pool, a steel cage is formed out of re-bar, and the gunite shell is shot over and surrounding it
  • Recirculate

    this setting bypasses the filter, water coming into the multiport does a U-turn and heads back towards the pool; used only when the filter is broken or when adding specialty chemicals, which specify using this setting


    amount of measurable bromine remaining after treating the water with bromine

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    1. soluble chemical compound that reduces the surface tension between two liquids
    2. used in many detergents and soapy cleaning compounds
  • Super Chlorination

    see shock treatment and breakpoint chlorination


    1. plumbing prior to and carrying water to the pump
    2. under vacuum pressure

    second line of defense is a basket at the pump; holes are smaller than those in a skimmer basket, and prevent the pump impeller from clogging


    see chelate


    1. discoloration or a colored deposit on the walls or bottom of a swimming pool or spa; most often, stains are metals, such as iron, copper and manganese; may appear as green, gray, brown or black; may discolor the water; sometimes a sequestering agent or chelating agent will remove them; if not, usually an acid wash is necessary to remove them from the walls and bottom
    2. stains are sometimes confused with scale

    see isocyanurates


    see cyanuric acid


    water that contains less than 100 ppm of calcium and magnesium; pools and spas should never be filled with soft water from a softener; water with less than 100 ppm of hardness should be increased to a minimum of 150-200 ppm using calcium chloride


    see soda ash

  • Sodium Thiosulfate

    1. chemical used to prevent false pH readings
    2. added to the water sample to remove chlorine prior to testing

    new technology that renders algae incapable of processing carbon dioxide, which they need to live


    chemical used to neutralize or de-chlorinate pool and spa water

  • Sodium Sesquicarbonate

    1. chemical mixture of equal parts soda ash and sodium bicarbonate used to increase pH and total alkalinity in pool and spa water
    2. has a pH of 10.1
  • Sodium Hypochlorite (NaOCI)

    1. inorganic chlorine in clear, liquid form
    2. provides 10 percent to 12 percent available chlorine; has a pH of 13 and requires that small amounts of acid be added to the pool to neutralize the high pH
    3. does not contain conditioner or stabilizer to protect it from sunlight, but it is protected if stabilizer or conditioner is already in the water

    1. active ingredient and chemical name of a non-chlorine shock treatment or non-chlorine oxidizer
    2. does not kill bacteria or algae, but it will oxidize or destroy ammonia, nitrogen and swimmer waster
    3. does not increase chlorine or bromine levels the way that superchlorination does, so water may be entered in 15 minutes after addition
    4. will not reactivate bromine

    to kill all living things, including bacteria and algae


    see dichlor

  • Sodium Dichloroisocyanurate Na(C3N3O3Cl2)

    1. granular organic chlorine that contains 62 percent available chlorine
    2. also known as sodium dichloro-s-triazinetrione

    see soda ash


    see dry acid

  • Sodium Bicarbonate (NaHCO3)

    pool additive (baking soda) used to raise total alkalinity


    1. sodium carbonate (Na2CO3)
    2. chemical used to counteract an acidic condition by raising pH
  • Shock Treatment

    extra large dose of chlorine applied every two weeks or as needed to kill algae and eliminate chloramines in the water


    practice of adding significant amounts of an oxidizing chemical (usually non chlorine oxidizers, such as sodium persulfate or potassium peroxymonosulfate) to the water to destroy ammonia and nitrogen compounds or swimmer waste


    1. describes the products used in shocking, such as hypochlorites, potassium permonysulfate or hydrogen peroxide
    2. act of bringing the sanitizer level up so high that breakpoint chlorination is reached; when breakpoint is reached, a "shock" is sent through the water, tearing apart molecules and slashing through cell walls
  • Sequestering Agent

    see chelant


    solid material settled out from the water

  • SCUM

    1. extraneous or foreign matter, which rises to the surface of the water and forms a layer or a film
    2. residue deposited on the tile or walls of the pool or spa
  • Scale

    see calcium carbonate

  • Saturation Index

    1. developed by Mr. Langelier
    2. a numerical value used to indicate whether pool water is out of balance (either scale-forming or corrosive); four factors are taken into account

    chemical agent used to remove unwanted contaminants

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  • Total Alkalinity

    1. amount of alkaline bicarbonate in pool water
    2. acts as a buffer to prevent fluctuations in pH

    total amount of chlorine in the water; includes both free available and combined chlorine

  • Total Dissolved Solids

    1. measure of the total amount of dissolved material in the water; maximum amount in pools is 2500 ppm, maximum in spas is 1500 over starting TDS; the only way to effectively lower TDS is to drain part or all of the water and replace it
    2. also called TDS

    1. slow-dissolving, tableted or granular, stabilized organic chlorine compound providing 90 percent available chlorine
    2. used for regular chlorination but must be dispensed using a floating feeder or an in-line feeder (chlorinator)
    3. contains an ingredient (cyanuric acid or stabilizer) that prevents the chlorine from being destroyed by the ultraviolet (UV) rays of the sun
    4. pH of 2.8, and regular trichlor tabs should not be placed in the skimmer, as the low pH will corrode the metal components in the equipment
  • Trichloroisocyanurate (C3N3O3Cl3)

    1. organic chlorine available in compressed tablets or sticks, containing 90 percent available chlorine
    2. also known as trichloro-s-triazinetrione

    cloudy condition of the water due to the presence of extremely fine particles in suspension that cannot be trapped by the filter because they are too small; adding a clarifier, such as an organic polymer or alum, will coagulate the particles and make the filter more efficient


    see tannin

  • Tannin

    1. harmless organic chemical that is leached out of new redwood or cedar hot tubs and is present in some source water
    2. also called tannic acid
  • TDS


    1. apparatus or device used to monitor specific chemical residuals, levels, constituents or demands in pool or spa water; kits usually contain reagents, vials, titrants, color comparators and other materials needed to perform tests; the most common pool and spa water tests are

    small plastic strips with pads attached that have been impregnated with reagents that can be used to test pool water for residuals, levels, constituents or demands; usually dipped in the water, and the resulting colors of the pads are compared to a standard set of colors to determine concentration

  • Titration

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    using UV wavelength radiation to destroy contaminants in water; UV light is also used to create ozone molecules for the same purpose

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    technology, which isolates nascent oxygen into a powerful sanitizing tool

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