FILL WATER:

FILM-X: (1) compound of citric acid used in cleaning plaster and other pool areas (2) safe replacement for muriatic acid

FOAMING: surface foam on water caused by high TDS levels

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

FLOCCULANT: see clarifier

FLOCCULATION: 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

HALOGENS: chemical elements either individually or collectively that constitute Group VIIB of the Periodic Table of Elements: fluorine, chlorine, bromine, iodine and astatine; only chlorine and bromine are used as disinfectants and sanitizers in pools and spas

HARD WATER: (1) water that is high in calcium hardness and other salts (2) resists soap being lathered

HARDNESS: (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

HERBICIDE: 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

HYDROGEN: (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

HYDROGEN PEROXIDE: 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

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

IONIZER: 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 

ISOCYANURATES: (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

LANGELIER INDEX: see saturation index

LIQUID ACID: see muriatic acid

LIQUID CHLORINE: (1) sodium hypochlorite (NaOCI) solutions (2) pool disinfectant

LITHIUM HYPOCHLORITE: (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

MAGNESIUM HARDNESS: (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

MINERAL: 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

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

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

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

NEUTRALIZER: chemical used to make chlorine or bromine harmless

NITROGEN: gas that causes algae to bloom and disables chlorine 

NON-CHLORINE SHOCK: (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

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

ORTHOTOLIDINE(OTO): see DPD

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

OVERDRAIN: (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

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

OZONE: 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