Acid: a substance with a pH of less than 7.0, which releases hydrogen ions when dissolved in water. Acids tend to dissolve metals and impart an unpleasant taste to drinking water. Learn more about acid water here.

Acidity: The low pH of a medium such as water, as measured by titration with a standard solution of sodium hydroxide and expressed either in parts per million or milligrams per liter of calcium carbonate equivalent.

Activated carbon: Also called activated charcoal, a porous, granular material produced by subjecting coal to high temperatures without oxygen. It is useful in water conditioning as a filtration material to bond to, or adsorb, organic matter and certain dissolved gases.

Alkalinity: The capacity of a medium such as water to neutralize an acid. Also, the measure of how much acid can be added to water without causing a significant change in pH.

Anion exchange: The process by which anions in solution are exchanged for other anions using an ion exchanger. In demineralization, bicarbonate, chloride and sulfate anions are exchanged for hydroxide anions from the anion exchange resin.

Arsenic: A toxic, odorless, tasteless semi-metal element which was once used in products like insecticides, pesticides and paints and also has a number of natural sources in the environment. It is found in significant concentrations in drinking water in many locations, notably in the northeastern US. Like many contaminants that enter drinking water supplies, arsenic is potentially hazardous at high levels and well owners are wise to test their water for its presence.

Automatic water softener: A water softener controlled by a timer which automatically runs through backwash and/or regeneration cycles at pre-determined intervals.

Backwash: A periodic process that subjects beds of filter material or ion exchange media to the opposite of service flow, which flushes out particulate material collected during the service period.

Bacteria: Micro-organisms, some of which can cause diseases in animals.

BIRM: Manganese dioxide-coated volcanic aluminum silicate (pumicite) used as an oxidizing-catalyst filter for iron and manganese reduction.

Bypass: A water line or connection which either supplies untreated water to a particular tap or permits untreated water to flow through the system while a water treatment unit is regenerated, backwashed or serviced.

Calcite: A natural source of calcium carbonate, CaCO3, found in limestone, marble, and chalk, and also a trade name for finely ground grades of marble or limestone which are used to reduce the acidity of water or filter out sediment.

Calcium: An element, Ca, which when dissolved in water, creates the calcium compounds that make water hard, as witnessed by the presence of distinctive residues.

Calcium carbonate: A chemical compound, CaCO3, found in nature as calcite in limestone, marble, and chalk as well as aragonite in pearls and in plant ashes, bones and shells.

Carbon dioxide: Odorless and colorless gas, CO2, present in the atmosphere and formed by the decay of organic matter, which dissolved in water forms carbonic acid, H2CO3.

Cartridge: A specified element containing a water filtering medium, ion exchanger, membrane, or other treatment medium which fits inside a housing to form a cartridge filter.

Cartridge filter: A water filtering device made up of a filter case or housing and a replaceable or renewable cartridge or element which can serve a single faucet, a whole house or a commercial application.

Cation: A positively-charged ion such as calcium, magnesium or sodium which, in an electrolyte solution, is attracted to a cathode via a difference in electrical potential.

Channeling: An impairment of a flow of water or solution through a filter or ion exchanger bed resulting from poor system design, inadequate flow rate, the fouling of the bed, the plugging of proper passages through it, or other system failures.

Check valve: A valve which allows water to pass only in one direction, preventing backflow.

Chloramines: Compounds which can form through a reaction between the ammonia and chlorine used to disinfect municipal water supplies. Unlike chlorine, chloramines do not form potentially dangerous trihalomethanes.

Chlorination: A process by which chlorine gas or solution is added to water as an agent of disinfection, control of microorganisms, or oxidation of impurities such as dissolved iron, manganese, hydrogen sulfide and organic matter.

Chlorine: A gas, Cl2, used in the disinfection of water and the oxidation of impurities like dissolved iron, manganese, hydrogen sulfide and organic matter.

Coliform bacteria: A type of bacteria, including E. coli, found in human and animal wastes. When present in water, these organisms are an indicator of the presence of dangerous fecal waste.

Cycle: The repeated exhaustion-regeneration process of an ion exchange system.

Dissolved solids: The weight of inorganic and organic matter in true solution in a volume of water.

Down-flow: The direction in which water or regenerant flows through an ion exchanger or filter during the operating cycle.

Drain: A pipe or conduit in a plumbing system which directs liquids downward by gravity.

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E.coli: An abbreviation of the name Escherichia coli, fecal coliform bacteria that is highly pathogenic if consumed by humans.

Efficiency: A measure of effectiveness or performance, such has of an ion exchange system, expressed as the amount of regenerant (salt) needed to produce a unit of hardness removal.

Escherichia coli: E.coli, fecal coliform bacteria that is highly pathogenic if consumed by humans.

Ferric iron: Rusty water caused by small particles of solid iron suspended in water which are removable through filtration.

Ferrous iron: So-called clear water iron, dissolved in water and best treated with a cation exchange water softener.

Filter: A device or system designed to improve upon undesirable taste, odor, turbidity, color, and/or particulates.

Filter media: Material used in a filter to prevent the passage of certain solids, either in suspension or in solution.

Flow control: A narrowing, valve or other devise designed to limit or restrict the flow of water or a regenerant.

Flow rate: The quantity, usually in gallons per minute, of water or regenerant passing a particular point over a specified unit of time.

Greensand: An olive-green sandstone mineral deposit from ancient seas which is used in water softeners due to its ion exchange properties.

Hardness: A characteristic of water, expressed as calcium carbonate equivalent in grains per gallon, parts per million or milligrams per liter, based on the presence of dissolved polyvalent cations, such as calcium, Ca+2, and magnesium, Mg+2. It causes scale formation in and on pipes, fixtures and water heaters, reducing their function, appearance and lifespan. Read more about fixing your water’s hardness here.

Hard water: Water containing total hardness of one grain per gallon or more measured as calcium carbonate equivalent.

Heavy metals: Undesirable and unhealthy metallic elements with high atomic weights, such as lead, mercury, chromium, cadmium and arsenic.

Hydrogen sulfide: A flammable, corrosive gas sometimes dissolved in well water, associated with the presence of iron and low pH. It causes a black precipitate in the presence of metals. Learn more here to see if hydrogen sulfide is present in your home.

Ion exchange: A reversible chemical process in which ions from a permanent medium, such as ion exchange resin, are exchanged for ions in a solution or fluid mixture. The direction of the exchange depends on the selective attraction of the ion exchanger for specific ions in the solution and their concentrations.

Iron: A metallic element, Fe, common in ground water, which can impart an unpleasant taste and/or stain clothing. Learn more about iron water here.

Iron bacteria: Iron-loving microorganisms which can collect in pipes and tanks to form brown, gelatinous ferric oxide slime, and eventually emerge as turbid water, causing staining and bad tastes and odors.

Iron fouling: A reduction in the capacity of a treatment medium due an accumulation of iron in the ion exchange resin bed or filter material.

KDF: Kinetic Degradation Fluxion, a patented medium composed of high purity copper and zinc granules capable of removing chlorine, soluble metals and other inorganic contaminants from water through a chemical reduction/oxidation (redox) process.

Lead: A heavy metal, Pb, once used in fuels, paints and plumbing materials, which is a potent neurotoxin if breathed or swallowed. It is especially dangerous to children.

Lime: The common name for calcium oxide, CaO, a widely-used chemical material.

Lime scale: Hard water scale formed in pipes and on fixtures, especially on the hot water side, containing a high percentage of calcium carbonate, CaCO3, or magnesium carbonate, MgCO3.

Limestone: A type of rock composed mostly of calcium carbonate with some magnesium carbonate.

Manganese: An element, Mn, commonly dissolved in ground water — often in the presence of iron – and causing problems similar to iron. It can be effectively dealt with by using a water softener.

Manganese greensand: Greensand coated with manganese oxide which is used in water treatment systems to remove insoluble ferric (oxidized) iron manganese and hydrogen sulfide.

Neutralizer: Alkaline matter, typically calcite (calcium carbonate) or magnesia (magnesium oxide), used to neutralize acid water.

Nitrate: A nitrogen compound, NO3, commonly found in ground water or surface water as the result of runoff from fertilizers, which can be harmful in high concentrations, especially to young infants.

pH: The scale that measures the degree of acidity or alkalinity of solutions, from 0 (highly acid) to 14 (highly alkaline), 7 being neutral.

Phosphate: A salt of phosphoric acid. Polyphosphates, in addition to being constituents in some detergents, are employed in water treatment as sequestering agents (bonding to and inactivating metal ions) to control iron and hardness, and as coating agents to control corrosion on metal surfaces. Polyphosphate sequestering is typically neither as effective nor as dependable as techniques like filtration and ion exchange water softening at removing iron, manganese and hardness minerals.

Potassium chloride: A colorless potassium salt, KCl, used as a regenerant in ion exchange water softeners and de-alkalizers.

Potassium permanganate: Soluble, crystalline material, KMnO4, used in water treatment as an oxidizer, disinfectant and regenerant for manganese oxidizing filters.

Pre-chlorination: The treatment of water with chlorine in advance of other treatment processes.

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Radon: A colorless, odorless, tasteless radioactive gas, Rn, occurring naturally from the decay of radium, considered carcinogenic when inhaled by humans. It can be effectively removed from water by aeration or filtration through activated carbon.

Regeneration: Restoration of the capacity of ion exchange or catalyst media for further use, also called recharging or rejuvenation, by washing with a chemical solution to displace contaminants which were deposited on the medium during the service run.

Resin: Synthetic ion exchange beads used in water softeners.

Resin cleaner: Chemical compounds used to clean ion exchange media of metals and organic material which have become bonded to the resin beads.

Reverse osmosis: A water treatment process that removes ionized salts, colloids, and organic molecules by forcing water through a semi-permeable membrane against the natural direction of osmosis, that is, from a more concentrated solution of impurities in water to a less concentrated solution, cleaner water. Learn more about the benefits of a reverse osmosis filter.

Rust remover: Any of a variety of liquid, powder or gel cleaning products, typically containing reducing agents like sodium hydrosulfite or acids, which remove rust stains, scale or lime deposits from fabrics, fixtures, appliances and kitchenware.

Scale: A deposit of mineral solids on and in water pipes, containers, fixtures and appliances through contact with water containing carbonates or bicarbonates of calcium and magnesium, especially when the water is heated.

Soda ash: Sodium carbonate, Na2CO3, used to neutralize acid water and in the lime-soda ash water softening process. It is also used in soap and detergent products.

Sodium chloride: Common salt, NaCl, used in the regeneration of ion exchange water softeners.

Soft water: Water which contains less than 1 grain per gallon, or 17.1 milligrams per liter of hardness minerals, expressed as calcium carbonate equivalent.

Softened water: Water treated to the point where it contains less than 1 grain per gallon or 17.1 milligrams per liter of hardness minerals, expressed as calcium carbonate equivalent.

Solar salt: Sodium chloride, NaCl, produced by solar evaporation in shallow ponds, used in the regeneration of ion exchange water softeners.

Sulfur: A yellow solid element, S. Sulfur water typically refers to water that smells and tastes unpleasant because it contains hydrogen sulfide gas.

Suspended solids: Undissolved solid particles in water.

Total hardness: Abbreviated TH, the sum of all hardness constituents in a water supply, including calcium and magnesium in solution along with metals like iron, expressed as calcium carbonate equivalent.

Total solids: Abbreviated TS, the weight of all organic and inorganic solids, both dissolved and suspended, per unit volume of water, as determined by the evaporation of a measured volume of water at 105° Celsius.

Turbidity: The amount of solid matter suspended as small particles in water, as measured by the degree of scattering and absorption of light in nephelometric turbidity units, or NTUs. Potable water should not exceed 0.5 NTUs.

Ultra filtration: Membrane filtration using hydrostatic pressure to separate impurities such as small colloids and large molecules from water that removes particles in the range of 0.002 to 0.1 microns along with organics with high molecular weights, but permitting ions and smaller organics to pass through.

Ultraviolet light: Electromagnetic radiation with a wavelength shorter than that of visible light, UV, which can be used to kill bacteria and viruses in water systems using an ultraviolet chamber.

Up-flow: Also called countercurrent flow, the phase of a water-treatment unit’s operational cycle when water or regenerant solution enters at the bottom of the vessel or column and flows out at the top, as opposed to down flow. A system can have up-flow during the treatment cycle and down-flow during regeneration, or vice versa, but regeneration flow and service flow always move in opposite directions.

Up-flow brining: Regenerating resin by forcing brine solution upward through the ion exchanger.

Up-flow softening: A pattern of water flow used in water softeners in which service flow moves upward through the ion exchange bed and regeneration flow moves downward, used at times to achieve higher operating efficiency.

Water conditioning: The treatment of water to improve its quality or to meet a given set of standards.

Water softener: A devise in which water is passed through a bed of ion exchange media, trading calcium and magnesium ions for sodium or potassium ions, producing softened water, which is more desirable for consumption as well as cooking, bathing, laundry and cleaning, or a chemical used in such a devise. Read more about the benefits of having a water softener in your home.

Water softener salt: Salt in crystal or pelletized form, such as sodium chloride, NaCl, or alternatively, potassium chloride, KCl, suitable for regenerating ion exchange water softeners.

Water softening: The process by which calcium and magnesium ions are removed from water, typically via the use of an ion exchange medium.

Water treatment device: A mechanism employed to improve a water supply by a variety of means, such as filtration, distillation, adsorption, ion exchange and reverse osmosis, among other techniques.

Water Quality Association: The WQA is an international trade association representing the household, commercial, light-industrial and small system water quality improvement industry.

Zeolites: Micro-porous, aluminosilicate minerals, such as manganese greensand, used for ion exchange beds in domestic and commercial water purification and water softening applications, including as catalyst/oxidizing filters to remove iron, hydrogen sulfide and manganese.

Zeolite softening: Also called base exchange, the removal of calcium and magnesium hardness from water using natural or synthetic zeolites.

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