Industry Glossary

Have you ever wanted to know what a Quat or a Steam Trap is? For your convenience, Fremont created this detailed glossary to help clarify industry-specific terminology from aerobic organism to planktonic and zeolite softener. We hope it helps foster a better understanding of what we do and how we can help you and your facilities. To keep up to date on water treatment terms refer to the glossary, or contact us if you have questions.

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  • ABMA

    American Boiler Manufactures Association.

  • Absorption

    Physical adhesion of molecules or colloids to the surface of solids without chemical reaction.

  • Absorption System

    Refrigeration system that uses lithium bromide as the refrigerant and steam as the means to pressurize the refrigerant.

  • Acid

    The hydrogen form of an ion.

  • Acid Cleaning

    Procedure for removal of waterside deposits in which an acid based material is used as the primary cleaning agent.

  • Aeration

    Process of introducing air into water.

  • Aerobic Organism

    An organism that requires oxygen for its respiration.

  • Agglomerate

    Gathering of fine particles or matter into a larger mass. See FLOC.

  • Air Washer

    System for removal of airborne contaminants or foulants from air flowing through cooling tower. Also regulates temperature or humidity by passing entering air though water spray chamber.

  • Airborne Contaminant

    Solids or gases brought into an open cooling system water in the air flowing through the tower.

  • Algae

    Simple plants. Under conditions favorable for their growth, they mature into colonies and produce mats of similar masses.

  • Algaecide

    Chemical treatment used to control growth of microorganisms in water systems.

  • Alkalinity

    Bicarbonate, carbonate or hydrate amounts in water. Usually expressed as “M” alkalinity to a methyl orange titration end point or “P” alkalinity to a phenolphthalein end point.

  • Ambient Temperature

    – Outdoor temperature as reported by periodic readings.
    – Also known as the dry bulb temperature, measured in the regular manner with conventional instruments.

  • Amine

    A class of chemical inhibitor used to control rate of corrosion in condensate return piping and related components. See FILMING AMINE, MORPHOLINE, NEUTRALIZING AMINE AND SOY AMINE.

  • Amorphous

    With a definite crystalline structure. Atoms or molecules not arranged in a definite pattern.

  • Amphoretic

    With a definite crystalline structure. Atoms or molecules not arranged in a definite pattern.

  • Anaerobe

    Type of microorganism which can exist without air or free oxygen.

  • Analysis

    Separation and measurement of component parts.

  • Anion

    Ion which carries a negative charge.

  • Anode

    Region of lower potential in a corrosion cell. Area of corrosion where metal is removed.

  • Anodic Inhibitor

    Corrosion inhibitor that forms a thin protective film over anode in a corrosion cell.

  • Antifoam

    Class of chemical treatment used in water to limit foaming of system water.

  • Antiprecipitant

    Chemical that retards the precipitation of insoluble salts, usually by interposing itself in the crystal structure.

  • Antiscalant

    Chemical that reacts with impurities to change chemical structure or which alters the action of the impurities.

  • Antiseptic

    Chemical that retards the growth of microorganisms.

  • Approach

    Temperature difference, in degrees, between the water leaving a cooling tower and the wet bulb temperature of the air entering the cooling water.

  • Aqueous

    Using water as a solvent.

  • ASME

    American Society of Mechanical Engineers

  • Association of Water Technologies (AWT)

    An international water treatment association representing over 500 companies that specialize in applying water treatments for industrial and commercial cooling and heating systems. AWT works to support members by providing the tools they need to succeed and grow — training, certification, networking, and regulatory and public awareness programs.

  • Atom

    The smallest unit of matter retaining the characteristics of an element.

  • Atomic Weight

    Method of comparing weight of an atom with that of an oxygen atom. Oxygen has an atomic weight of 16; hydrogen has an atomic weight of 1.

  • Attrition

    Breakage or wear of ion exchange resins.

  • Autoclave

    A chamber for sterilizing with steam under pressure.

  • Back Pressure

    Pressure exerted against a flow.

  • Backwash

    Upward flow of water through a resin bed to cleanse, expand and classify the resin.

  • Bacteria

    Large group of one cell microorganisms. Some strains can produce very adhesive, dense slime type deposits on waterside surfaces of heat exchanger in cooling system.

  • Base

    The hydroxyl form of a cation or a compound that can neutralize an acid.

  • Basin

    Lower area of system which system water collects, i.e., bottom area of cooling tower.

  • Bed

    Area in an ion exchanger containing resin or exchange medium.

  • Bed Depth

    Height of resinous material in bed exchanger after exchanger has been properly conditioned for operation.

  • Bed Expansion

    Effect produced during backwashing of exchanger.

  • Bed Volume

    The amount of space occupied by the resin bed in cubic feet or gallons.

  • BHP


  • Bicarbonate Alkalinity

    Presence in a solution of hydroxyl (OH-) ions resulting from the hydrolysis of carbonates and bicarbonates.

  • Binder

    Substance which causes particulates to bond together.

  • Biocide

    Group of internal chemical treatments used to control growth of microorganisms (algae, bacteria, fungi) in cooling tower and closed loop systems.

  • Biofilm

    An aggregate of microorganisms in which cells adhere to each other and/or to a surface. Biofilms may form on living or non-living surfaces, and represent a prevalent mode of microbial life in natural, industrial and hospital settings.

  • Biological Deposit

    Deposits of microorganisms, or by-products of their life processes, on waterside surfaces.

  • Bleed

    Intentional draining of a portion of system water from cooling tower recirculating system to drain. Means of controlling concentration of dissolved solids in system water.

  • Bleed Rate

    Rate at which water is bled from cooling tower recirculating system.

  • Blister

    Partial or complete failure of boiler tube due to overheating.

  • Blowdown

    Intentional wasting or draining of water from boiler system to waste. Means to removing sludge from system and also controlling concentration of dissolved solids in system water.

  • BOD

    Also known as Biological Oxygen Demand, a chemical procedure.

  • Boiler Code

    A set of rules and specifications for designing, constructing, inspecting and operating boilers.

  • Boiler Horsepower

    By definition, the generation of 34.5 lbs. steam/hour from and at 212F°. By common acceptance, 10 sq. ft. of heating surface is one rated power horsepower.

  • Boiler Scale

    Relatively hard and adherent deposit on waterside surface of boiler. By analysis contains high percentage of calcium, magnesium, iron oxide and by-products of internal chemical treatments.

  • Brine

    A salt solution, generally sodium chloride.

  • BTU

    Stands for British Thermal Unit.

  • Ca

    Chemical symbol for calcium.

  • CaCO3

    Chemical symbol for calcium carbonate.

  • CaH

    Symbol for calcium hardness.

  • Calcium Bicarbonate

    Results of chemical reaction between carbon dioxide, calcium carbonate and water.

  • Calcium Carbonate

    The precipitant resulting from heating of the water that contains calcium bicarbonate.

  • Capacity

    Absorption ability possessed by ion exchange material.

  • Carbon Alkalinity


  • Carbon Dioxide

    Corrosive gas found in most surface and ground water supplies. Released in the chemical reactions that occur in boiler system water.

  • Carbonate Cycle

    A method of internal boiler water treatment in which calcium carbonate is precipitated in the presence of an organic polymer dispersing agent.

  • Carbonic Acid

    Acid produced from the mixture of carbon dioxide and water.

  • Carry Over

    Condition which develops in boiler water resulting in solids and/or chemical treatment being carried out of the system as part of the steam.

  • Catalysis

    Addition of a material (catalyst) that does not take a direct part in a chemical reaction, but serves to increase the rate of the reaction.

  • Cathode

    Region of higher potential in a corrosion cell.

  • Cathodic Inhibitor

    Corrosion inhibitor that forms a protective film on the cathode surface of a corrosion cell.

  • Cathodic Polarization

    Method of inhibiting corrosion by preventing the diffusion, or flow of oxygen, to the cathode site of a corrosion cell.

  • Cation

    Ion which carries a positive electrical charge.

  • Cavitation

    Metal attack resulting from high flow velocity, variable pressure situations in water containing dissolved or entrained gas. Evidence of cavitations is often deep circular pits.

  • Centrifugal System

    Compressor type cooling system.

  • Certified Water Technologist (CWT)

    Certified Water Technologists (CWTs) have the expertise, experience, and knowledge to provide the highest standards of service to and oversight of boilers and chillers. They pride themselves on making facilities as efficient as possible using the latest water treatment technology and techniques to save energy. Individuals with the CWT designation have personally committed themselves to excellence in the water treatment industry.

  • Channeling

    The flow of water or solution taking the “least line of resistance” through a resin bead.

  • Chelant

    A sequestrant that prevents an ion from exhibiting its normal properties by complexing (bonding) with it.

  • Chemicaloxygen Demand

    Amount of oxygen, expressed in parts per million, consumed under specified conditions in the oxidation of organic matter contained in water.

  • Chloride

    Acid radical contained in both surface and ground water supplies.

  • Chloride Test

    Test performed on water sample to determine total amount of chlorides present. Results expressed in ppm. Recommended upper limits to which chlorides can build in system water provides a method for controlling waterside deposits. Amount of chloride in system water compared to chloride content of makeup or feedwater, provided the means of determining ‘cycles of concentration’ at which a system is operating.

  • Chlorinated Phenolic

    Non-oxidizing biocide used to control growth of microorganisms in cooling tower recirculating system water.

  • Chlorinator

    A device used to meter chlorine into a cooling water at a preselected rate.

  • Chlorine

    Oxidizing type biocide. Used to control growth of microorganisms in cooling tower system water.

  • Chlorine Demand

    Amount of chlorine, expressed in parts per million, required to achieve chlorination.

  • Chlorine Residual

    Amount of available chlorine present in the system water at any specific time.

  • Chromate

    Anodic type corrosion inhibitor that forms a highly passive film of ferric and chromate oxide on the anode of a corrosion cell.

  • Circulating Hot Water System

    System in which water is heated and circulated through a system of piping, or to a heat exchanger. In circulating through the system, heat in water is transferred and utilized for space heating, heating of potable water and/or used to clean and sanitize.

  • Clarification

    External treatment processes which removes suspended solids, turbidity, color and colloidal matter from makeup water.

  • Closed System

    System in which water is continuously recirculated and loss of water from the system is less than 5% of recirculating rate.

  • Coagulation

    To bring together small particles into a single large mass which can be filtered or settled out of solution.

  • Coalescence

    Process describing the growing together of several different particulates into one larger body.

  • COD

    Abbreviation for CHEMICAL OXYGEN DEMAND.

  • Collodial

    The production of both steam and electricity in the same plant.

  • Collodial

    Composed of extremely small size particles which are not removed by normal filtration.

  • CONC

    Abbreviation for concentration.

  • Condensate

    Water condensed from steam.

  • Condensate Polisher

    Ion exchange resins being used to remove or exchange ions as well as to filter condensate for reuse in steam cycle.

  • Condensate Tank

    Tank or reservoir in a steam boiler system to which condensate flows and collects.

  • Condenser

    Heat exchanger in cooling system in which refrigerant gas gives up heat to tower recirculating water.

  • Conductance

    A measure of the ability of water to conduct an electric current.

  • Conductivity

    The ability of electrical current to flow through water as a measure of its ion content in mhos/cm or micromhos/cm.

  • Conductivity Test

    Test made on any water sample with a conductivity meter to determine amount of total solids present. Results expressed in ‘micromhos’, ‘mho’ or ‘conductivity’. Test results are utilized to control solids in system water within limits to prevent deposition.

  • Contaminate

    Any solid, gas or liquid in system water that is foreign and not normally found under the conditions of operation.

  • Continuous Blowdown

    Intentional, controlled, continuous flow of boiler system water taken from the top or upper section of boiler to drain.

  • Convection

    Transference to heat by circulation of the heated parts of gas or liquid whereby heated portions are lighter and rise vertically.

  • Cooling Pond

    Large body of water (pond or small lake) to which cooling water is pumped and heat contained in water is released to atmosphere by natural evaporation.

  • Cooling Range

    Numerical difference between temperature of water entering top of cooling tower and the temperature of water leaving the basin or sump of the tower.

  • Cooling Tower

    Device for the evaporative cooling of water by contact with air. Achieved partially by an exchange of latent heat resulting from evaporation of some of the circulating water, and partially by transfer of sensible heat to the air.

  • Copolymer

    Polymerization of different monomers on the backbone of a polymer or on its branch chains.

  • Corrosion

    Electrochemical process in which a difference in electrical potential develops between metals or between different sites of the same metal. The difference in potential results in metal being removed at the anode site.

  • Corrosion Cell

    Two points on different metals, or different sites of the same metal, consisting of an anode and cathode. Difference in electrical potential between the two points results in metal being removed at the anode site.

  • Corrosion Coupon

    Test metal strip used to measure the rate of corrosion.

  • Corrosion Products

    Metal removed as a result of the corrosion process.

  • Corrosion Strip


  • Counter Flow Tower

    Tower where air movement and hot water mix at 180°to each other with air moving vertically through tower fill packing.

  • Crevice Corrosion

    Corrosion taking place where specific area is isolated from bulk solution, i.e., flange area.

  • Cross Contamination

    Intermixing of one resin with another of an opposite charge or of two water streams.

  • Cross Flow Tower

    Tower in which air movement and hot water mix at 90°or cross to each other with air moving horizontally through the fill packing and falling water.

  • Cross Linkage

    The connection between two or more polymer chains to tie them together, as is done by DVB.

  • Cu

    Chemical symbol for copper.

  • Cuprous Metal

    Metal containing copper.

  • Cuprous Oxide

    Passivated oxide state of copper.

  • Cycles Of Concentration

    Ration between the amount of dissolved solids in makeup water and amount of dissolved solids in system water.

  • Cyclohexylamine

    Neutralizing type amine. Used to help control rate of corrosion in condensate return system of steam boiler.

  • Deaerator

    External treatment equipment in which boiler feedwater is heated to 212F°+ for the purpose of releasing dissolved oxygen from the water.

  • Dealkalization

    External treatment process by which natural alkalinity or raw makeup water is lowered.

  • Defoamer


  • Deionization

    General term which embraces the removal of all charge ionizable salts (both organic and inorganic) from solution.

  • Deionization

    General term which embraces the removal of all charge ionizable salts (both organic and inorganic) from solution.

  • Deionize

    To remove ions from solution.

  • Deionizer

    External treatment process in which raw makeup water, under pressure, passes through a membrane and in the process dissolved solids are removed.

  • Delingnification

    Loosening of surface fibers in cooling tower wood members causing a weakening of the timber.

  • Demineralize

    Removal from solution or inorganic salts by means of adsorption by ion exchange.

  • Depolarization

    Any change in the potential of either the anode or cathode or both, which increases the driving force of the corrosion reaction.

  • Deposition

    General term describing accumulation of matter on waterside surface of heating or cooling equipment. Can be hard scale, sludge, iron oxide, foulants, biological deposits.

  • Design Tonnage

    Parameters for which a cooling tower is built. Expressed as cooling a given GPM flow of water entering the tower at a specified temperature-cooling through a given range-leaving the tower at the required temperature.

  • Developed Tonnage

    Actual amount of cooling being performed by system. If system was designed for a 10°cooling range, and water falling through tower is cooled by 5°F, system would have developed tonnage of 50%.

  • Dew Point

    Temperature at which a given mixture of air and water will have a relative humidity of 100% saturation.

  • Dezincification

    Leaching of zinc from brass.

  • Di Water

    Useable discharge from dionizer.

  • Diffusion

    Spontaneous process of equalization of physical states, i.e., one gas liberated in another.

  • Disciccant

    Moisture absorbing material, i.e., quick lime, silica gel, activated alumina. Used to control condensation in boiler during dry lay-up.

  • Dispersant

    Chemical which causes particulates in water to remain in suspension.

  • Dissociate

    The process of ionization of an electrolyte or a salt upon being dissolved in water, forming ions of cation and anion.

  • Dissolved Matter

    Matter, exclusive of gases, present in water.

  • Dissolved Oxygen

    Oxygen which has been freed from compounds contained in natural water supplies.

  • Dissolved Solids

    Minerals in surface and ground water supplies which have been dissolved from contact with earth’s surface.

  • Distribution Deck

    Area on top of cooling tower into which water, containing heat, is dumped.

  • Distribution System

    Mechanical method of uniformly distributing hot water over the fill area inside the tower preparatory to cooling. Low pressure spray through the piping and nozzles is normally used in counter-flow tower, and gravity drop in cross-flow tower.

  • Drift

    Water droplets which are entrained in the airstream as it passes through the tower. Water entrained is carried out of the tower and lost to the atmosphere.

  • Drift Eliminator

    Baffling in cooling tower that causes hot air, with entrained droplets, to change direction a number of times causing the droplets to hit eliminator surfaces and fall back into the tower water.

  • Drum Vent

    Valve on the top of boiler drum. Used to vent air from boiler at “start up” or when boiler is cooling down.

  • Dry Bulb

    Ambient temperature of air measured in standard manner with conventional instruments.

  • Dry Lay-up

    Period during which equipment or system is non-operational and all water drained and system is left dry.

  • DS

    Abbreviation for dissolved solids.

  • Economizer

    Heat exchanger placed in gas passage between boiler and stack. Designed to recover heat.

  • EDTA

    Abbreviation for ETHYLENEDIAMINE TETRAACETIC ACID. Chemical referred to as a “chelant”. Forms heat stable complex with calcium, magnesium, iron and copper.

  • Eductor

    A device that, by flow of water through it creating a vacuum, draws a solution into the water stream passing through it.

  • Effluent

    Flow of water out of a tank or from system.

  • Electric Boiler

    Unit for production of steam by heating water with electrical resistance elements, or by passing AC current through the water between electrodes.

  • Electrodes

    Conductive materials placed in water solution which have a positive or negative charge.

  • Electrolyte

    Material that when dissolved in water form ions which are capable of carrying current.

  • Electron

    A sub atomic particle with a negative electrical charge.

  • Electroneutrality

    Where the positive electrical charge equals the negative charge.

  • Elution

    To remove ions from a resin by passing other ions in solution of higher concentration or affinity through the resin bed.

  • Emulsion

    A colloidal dispersion of one liquid in another.

  • Enthalpy

    Total heat content, which is the sum of the sensible heat of the air and water vapor, plus the latent heat of vaporization of the water.

  • Entrained

    To carry or draw along. The transport of water in a gas or vapor stream.

  • Equation

    An expression of a reaction using chemical symbols.

  • Equilibrium

    The stage in a reversible reaction when there is no driving force in either direction.

  • Equilibrium Reactions

    Interaction of ionizable compounds in which the products obtained tend to revert to substances from which they were formed until a balance is reached in which both reactions and product are present in definite ratios.

  • Equivalent

    Equal valance.

  • Erosion

    Form of corrosive attack associated with metal removal due to high water velocity.

  • Ethylenediamine Tetraacetic Acid

    See EDTA.

  • Eutrophication

    The process by which a lake ages.

  • Evaporation Loss

    Portion of tower recirculating water lost to the atmosphere in the process of rejecting heat from tower recirculating water. Amount lost varies depending on level of heat contained in tower water.

  • Evaporative Condenser

    System in which condenser or heat exchanger is located in the cooling tower. Water is sprayed from nozzles above condenser, while air is blown across condenser tubes or coil. Refrigerant, inside condenser tubes, is cooled due to the extraction of heat from the refrigerant gas caused by the evaporation of water on the outside of the condenser tubes.

  • Evaporative Cooling

    Cooling by evaporation of water, heat for which is supplied by air.

  • Evaporator

    Heat exchanger in which chill water or air gives up heat it contains to refrigerant gas.

  • Exchange Site

    Reactive groups on an ion exchange resin.

  • Exhaustion

    State in which resin in water softener is no longer capable of ion exchange.

  • Exotherm

    Giving off heat in reaction or solution of a substance.

  • External Treatment

    Any process of procedure which removes or reduces solids or gases from water before it enters the boiler or cooling tower system water.

  • Extrapolation

    Extending information beyond the point where proven data is available.

  • Fan

    An air foil rotating to move air through cooling tower. Mounted on top of tower (induced draft) or side of tower (forced draft).

  • Fan Stack

    Tower fan housing.

  • Fe

    Chemical symbol for iron.

  • Feedwater

    Water feed to boiler. Can be a mixture of condensate and raw makeup, all condensate, or all raw makeup depending on operating conditions.

  • Ferric Oxide

    Metal removed in corrosion of iron bearing metal.

  • Ferrous Metal

    Metal constructed from iron, i.e., cast iron, nickel, iron, galvanized steel, silicon, stainless steel.

  • Fill

    Structural material within cooling tower that facilitates contact between water and air. See FILL PACKING, SLATS, SPLASH PACKING, TOWER FILL.

  • Fill Packing

    Fill material such as cross-fluting designed to distribute water in thin film in a cooling tower.

  • Filming Amine

    Class of inhibitor used to control corrosion in condensate return portion of steam boiler system. Forms an adherent non-wettable organic film on metal surface thereby preventing contact between metal surface and corrosive condensate water.

  • Filming Inhibitor

    General term applied to any treatment which forms an adherent non-wettable film on metal surface preventing contact between metal and system water.

  • Filter

    Porous media through which a liquid may be passed to effect removal of suspended matter.

  • Filtrate

    Liquid which passes through a filter.

  • Filtration

    External treatment process in which water passes over a filter bed of granular material to effect removal of suspended matter.

  • Fines

    Resin particles smaller than 50 mesh.

  • Fire Tube Boiler

    Term used to describe a boiler in which tubes are surrounded by water and fire, and gases pass through inside of boiler tube.

  • Flash Tank

    Tank into which blowdown from boiler is introduced. Part of water flashes into steam; remainder is removed from tank as a liquid.

  • Floc

    Clump of solids formed in water.

  • Flocculant

    Chemical which attaches itself to foulant particles creating a low density, light, fluffy floc that will have little tendency to adhere to metal surfaces. Floc usually settles or precipitates in the solution.

  • FMA

    Abbreviation for free mineral acid or, sum of the mineral acids.

  • Foaming

    Small, stable, noncoalesing bubbles formed on water surface in boiler. Extreme foaming is leading cause of ‘carryover’.

  • Fog

    Symbol for fats, oil and grease in water analysis.

  • Forced Draft Tower

    Type of cooling tower in which air intake is at bottom and air is forced up and through tower.

  • Foulant

    Term loosely used to define any type deposit composed of silt, organics, particulates scrubbed from atmosphere, microbiological deposition, dirt, etc.

  • Free Available Chlorine

    Refers to any unreacted chlorine present in system water.

  • Free Base

    The regenerated form of a weak base anion resin.

  • Free Co2

    Dissolved carbon dioxide gas in water.

  • Freeboard

    The space above the resin bed to accommodate resin expansion in backwash step of regeneration.

  • Fungicide

    Chemical that kills fungi.

  • Fungus

    A simple plant, containing no chlorophyll and not differentiated into roots, stems or leaves.

  • Galvanic Corrosion

    Corrosion that occurs when two dissimilar metals are in contact with solution.

  • Galvanic Series

    Table listing metals according to their ability to resist corrosion.

  • General Corrosion

    Metal attack that is uniformly distributed over a surface. See UNIFORM CORROSION andUNIFORM THINNING.

  • GPD

    Symbol for gallons per day.

  • GPG

    Symbol for grains per gallon.

  • GPH

    Symbol for gallons per hour.

  • Graphitization

    Selective loss of iron from cast iron.

  • Gravimetric

    Measurement by weight.

  • Greensands

    Neutrally occurring materials composed primarily of complex silicates, which possesses ion exchange properties.

  • Grooving

    Term describing corrosion of condensate piping due to carbonic acid attack. Characterized by development of a groove or flat area in the bottom portion of condensate piping.

  • Ground Water

    Portion of water which percolates into the earth’s crust and collects in subterranean pools and underground rivers. Source of well and spring water.

  • Handhole

    An opening in boiler drum or water leg which permits limited visual inspections of internal waterside surfaces.

  • Hardness

    A characteristic of water quality generally accepted to represent the total concentration of calcium and magnesium ions.

  • Hardness Test

    Test performed on water sample to determine the presence or absence of the elements of calcium or magnesium. Results expressed in ppm. Calcium and magnesium minerals are the principal cause of scale deposits.

  • Heat Exchanger

    Equipment in which heat is transferred from one medium to another.

  • Heat Load

    Amount of heat dissipated in a cooling tower measured in BTU’s.

  • Heat Pump

    Closed loop system used to extract low-level heat from one medium, normally air or water, boost its temperature and release it into another medium.

  • High Head

    Term used loosely to indicate pressure of refrigerant gas in compressor higher that it should be at a specified load condition.

  • High Pressure Boiler

    Relative term used to indicate boiler operating pressure. Generally indicates boiler operating at or above 600 psig.

  • Hot Well

    Closed or open tank in which condensate water is stored.

  • Hp

    Stands for horsepower.

  • Hydraulics

    A movement or action resulting from liquid flow.

  • Hydrometer

    A device to measure specific gravity of fluids.

  • Hydrophilic

    Term which means to attract water.

  • Hydrophobic

    Term which means to repel water.

  • Hydroxyl

    Term used to describe the OH radical.

  • Hyperbolic Tower

    Chimney or natural draft type cooling tower.

  • Hypochlorite

    Basic chemical containing chlorine.

  • Impingement

    Metal attack usually due to turbulent flow of water high in dissolved or suspended solids or entrained gases. Results in horseshoe shaped pits.

  • Indicator

    Substance that gives visible change, usually of color, at a desired point in a chemical reaction.

  • Induced Draft Tower

    Cooling tower with air mover or fan on top of tower pulling air through the tower fill and out through the loop.

  • Influent

    A liquid flow into a system.

  • Inhibitor

    Generally used to indicate any chemical that aids in control of corrosion. Also used to indicate some treatments which inhibit scale formation.

  • Inorganic Matter

    Matter composed of other than plant or animal matter.

  • Interface

    Point where two substances are in contact one with another.

  • Interlock

    A device which will prevent one action from happening while another action is proceeding.

  • Internal Treatment

    Chemical treatment added to system water to aid in controlling corrosion, prevention of waterside deposits or control of microbiological growth.

  • Ion

    An atom or radical in solution carrying an integral electrical charge either positive (cation) or negative (anion).

  • Ion Exchange

    The interchange of one ion in solution with another ion on an insoluble material.

  • Ionization

    Dissociation of molecules into charged positive or negative particles.

  • Iron Fouling

    Plugging of piping, nozzles, etc. with iron oxide or rust.

  • Iron Oxide

    Metal removed in corrosion process from iron bearing metals.

  • Iron Related Bacteria

    Uses the abbreviation of IRB and is a bacteria which assimilates iron and excretes its compounds in their life process.

  • Langelier Index

    An index used to determine the scaling or corrosive tendencies of water.

  • Latent Heat

    Heat required to change a liquid into a vapor without change of temperature or pressure.

  • Layered Orstratified Bed

    Resins with sufficient difference in density and hydraulic characteristics to be layered in the same tank in place of two separate tanks.

  • Leakage Or Slippage

    The amount of an ion or ions coming from a resin bead during the service cycle.

  • Legionellapneumophila

    Legionella pneumophila is a motile, rod-shaped, gram-negative, aerobic, bacterium. It is considered to be a “facultative parasite,” which has been identified as the leading cause of Legionnaires’ Disease.

  • Lignin

    Major non-cellulose constituent of wood.

  • Lime Soda Softner

    Water softener employing calcium hydrate and sodium carbonate as the reacting chemicals.

  • Load

    Term used to express the amount of steam produced by a boiler or heat being rejected by a cooling tower when compared to amount for which system was designed. If producing or rejecting one half of its designed or rated capacity, system is said to be operating at 50% of load.

  • Louver

    Baffle used for purpose of changing the direction of air flow in a cooling tower. Also to prevent water droplets from splashing out of cooling tower on descent through the structure.

  • Low Boiler Pressure

    Relative term used to indicate boilers operating below 450 psig.

  • M Alkalinity

    Water in which hydrogen ions (acid) predominate, causing pH to be somewhere in a pH range of 4.2-8.4.

  • Macroporous

    Having large pores.

  • Magnetite

    The black magnetic, protective film of Fe3O4 normally present on surfaces of steel.

  • Makeup Tube

    Downcomer, supply tube are common tubes used to indicate tubes where circulation of water is down.

  • Makeup Water

    Treated or untreated water introduced into a system to replace any losses.

  • Manhole

    Opening in boiler or tank that permits a man to crawl through for internal inspection.

  • Mechanicaldraft Tower

    Cooling tower in which air is constantly being moved over water falling through the tower by fans located on the side of the tower.

  • Membrane

    A barrier, usually thin, that permits passage only of particles up to a certain size or of specific nature.

  • Metabolic

    Undergoing or pertaining to a change in state.

  • Metabolize

    To convert food, such as organic matter, to cellular material and gaseous by products by biological process.

  • MHO

    Abbreviation for micromho.

  • Microbiocide

    A chemical toxic to microorganisms.

  • Micromho

    Basic unit of electrical conductance.

  • Microorganism

    Organisms that cannot be seen with the naked eye. In water treatment they usually refer to organisms that grow in cooling tower environment, i.e., algae, bacteria, fungi.

  • MIL

    Measurement of thickness or depth. Term used in water treatment to express degree of metal loss due to corrosion.

  • Mill Scale

    Matter formed on iron or steel in the process of production. Consists mainly of magnetic iron oxide.

  • Mixed Beddemineralizer

    External treatment process consisting of a series or system of strong cation or strong anion, weak base anion, mixed bed decarbonator or vacuum deaerator exchange.

  • Mn

    Chemical symbol for manganese.

  • Molecule

    The smallest unit of matter retaining properties of a compound.

  • Molybdate

    Filming type of corrosion inhibitor that forms a passivating film on the anode of a corrosion cell.

  • Monomer

    A single reactive molecule capable of combining with another like itself or another different monomer to form a polymer.

  • Monomolecular

    A film that is one molecule thick.

  • Morpholine

    Chemical treatment utilized to neutralize carbonic acid in condensate return portion of steam boiler system.

  • MPY

    Abbreviation of mils per year. Used to express rate of corrosion.

  • Mud Drum

    Lower drum of boiler where insoluble sludge collects.

  • NACE

    National Association of Corrosion Engineers.

  • NaCl

    Chemical symbol for salt.

  • Natural Draft Tower

    Tower in which the air movement through it is dependant only upon atmospheric conditions.

  • Negative Charge

    Electrical potential which an atom acquires when it gains one or more electrons.

  • Neutral

    In pH terms, 7; neither acid nor alkaline.

  • Neutralizing Amine

    A class of inhibitors that neutralizes carbonic acid by elevating the pH of condensate water from acid to an alkaline state.

  • Nitrate

    Nitrogen as nitrates.

  • Nitrite

    An anodic inhibitor that induces metal to form its own impervious film at the anode site in a corrosion cell.

  • Noble Metal

    Metals that are insoluble to any pH, i.e., titanium, molybdenum, nickel.

  • Non-ferrous

    Metal which does not contain any iron, i.e., cooper, brass, zinc, aluminum.

  • Non-oxidizing Toxicant

    Class of biocide that function by adsorbing onto the microorganism’s cell wall.

  • Nozzles

    Water spouts in distribution decking of a cooling tower. Breaks up the returning water into droplets and distributes them uniformly over the top of the fill.

  • NSF

    National Sanitary Foundation

  • NTA

    Abbreviation for Nitrilotriacetic Acid. Used to prevent scaling in boilers and/or as an acid in selective metal deposit control, i.e., iron and manganese in both boilers and cooling towers.

  • O2

    Chemical symbol for oxygen.

  • Off The Line

    Term used to denote a system that is in short or long term layup.

  • Oh Alkalinity


  • OHM

    A unit of resistance to the passing electric current.

  • On Linestream Cleaning

    Method of removing waterside deposits while system remains in operation.

  • Once Through System

    Any system in which water is only used once and then put to the drain.

  • Openfeedwater Heater

    Tank in which feedwater is heated by steam, but where temperature does not go above atmospheric.

  • Organics

    Carbon containing compounds generally from vegetation or non-mineral origin.

  • Organo-tin

    Non-oxidizing “heavy metal” inorganic biocide used for the control of microorganisms in system water.

  • Orthophosphate

    1. Internal chemical treatment that functions as an anodic inhibitor or antiscalant. 2. A sludge resulting from the revision of polyphosphate.

  • Osmosis

    Process where water on one side of a membrane tries to pass through the membrane to dilute a salt solution on the other side in an attempt to equalize the concentration of salt on both sides.

  • Oxidation

    The addition of oxygen, the removal of hydrogen, or the loss of electrons.

  • Oxide

    A compound composed of metal and oxygen.

  • Oxygen

    An element occurring free as a colorless, tasteless, odorless gas.

  • Oxygen Scavenger

    Chemical used in treatment of boilers to reduce last traces of dissolved oxygen in system water. Sodium sulfite most widely used type.

  • P Alkalinity

    Water in which hydroxyl ions (alkaline) predominate, causing pH of system water to be above 8.2. Also referred to as caustic, OH or carbonate alkalinity.

  • Packaged Boiler

    A shop assembled steam boiler generator with necessary auxiliary equipment complete and ready to use.

  • Packing

    Slats, baffling or corrugated fill found inside the casing of a cooling tower.

  • Parameters

    Two figures indicating an upper and lower limit.

  • Particulate Matter

    Any matter, exclusive of gases, existing in a non-liquid state of water.

  • Passivation

    The transformation of a metallic surface to a state in which it does not readily oxidize. Usually accomplished by forming a protective film on metal surface.

  • pH

    A measure of the concentration of hydrogen ions in water. pH is a number between 0 and 14, denoting various degree of acidity or alkalinity. Neutral water has a pH of 7. Values below 7 and approaching 0 are increasingly acid while values from 7 to 14 are increasing alkaline.

  • Phosphate

    Chemical used in treatment of boilers that aids in prevention of scale type deposits.

  • Phosphonate

    1. Cathodic corrosion inhibitor for ferrous metal. 2. Deposit control agent.

  • Pitting

    Term that describes localized attack on metal surface. Results in crater-like indentations in metal.

  • Pitting Factor

    Ratio of a pit to the average depth of metal penetration.

  • Planktonic

    Floating or swimming in water.

  • PO4

    Chemical symbol of phosphate.

  • Polorization

    Extent of potential change in volts, caused by net flow of current to or from an electrode. When there is no difference in potential between the anode and cathode, corrosion ceases and the metal is said to be in a “passive” state.

  • Polyacrylate

    Synthetic polymer formed from monomers. Used as a boiler and cooling water dispersing agent.

  • Polyelectrolyte

    A high molecular weight water soluble polymer with high charge density or multi-charged ions.

  • Polymer

    Synthetic chemicals with long chain molecules of repeating units.

  • Polymerization

    The act of reacting monomers to form a long chain polymer.

  • Porosity

    The degree of openness or a sponge-like quality.

  • Positive Charge

    The electrical potential acquired by an atom which has lost one or more electrons.

  • Potable Water

    Water which meets drinking water quality standards.

  • PPB

    Stands for parts per billion.

  • PPM

    Stands for parts per million.

  • Precipitate

    Matter that has separated out of solution as a result of chemical reaction or physical change.

  • Precipitating Program

    A treatment program that results in precipitation from solution to scale forming contaminates in the form of non-adhering sludge.

  • Pressure Drop

    Static pressure or amount of resistance in air or liquid caused by system piping or obstructions in system fabrication.

  • Pretreatment

    Any process or procedure which removes or reduces solids or gases from water before it enters the system.

  • Priming

    Spasmodic actions resulting in spouting or surging of boiler water into steam header or outlet.

  • Process Steam

    Steam used to heat or operate some manufacturing process.

  • Process Water

    Water used in a product or in manufacture of a product.

  • Pumping Head

    Energy required to raise water and overcome friction losses inherent in fabrication of the system.

  • QUAT

    Stands for Quaternary ammonium cations that are positively charged polyatomic ions of the structure NR4+, R being an alkyl group. Unlike the ammonium ion (NH4+) and the primary, secondary, or tertiary ammonium cations, the quaternary ammonium cations are permanently charged, independent of the pH of their solution.

  • Radiant Heat

    Heat supplied by radiation without necessity of some medium transmission, i.e., heat from the sun.

  • Range

    Numerical difference between the water temperature entering the cooling tower at the top, and the cold water leaving the basin or sump at the bottom of the tower.

  • Rated Tonnage

    Thermal parameters for which a cooling tower was designed.

  • Raw Water

    Natural water as it comes from the environment or municipal water treatment plant.

  • Reagent

    Any substance which, from its capacity for certain reactions, is used in detecting, examining or measuring other substances.

  • Receiver

    Tank or reservoir to which steam condensate flows and makeup water is introduced into boiler system.

  • Regenerant

    A chemical used to restore the ion exchange resin back to its desired form.

  • Regeneration

    Process by which an ion exchanger is restored to its operative form. Water softener regeneration involves four steps; backwash, brining, slow rinse and fast rinse.

  • Reheat

    Returning partially expanded steam to a boiler so that additional heat is added before the steam passes through the final stages of a turbine.

  • Relative Humidity

    Ration of water vapor pressure in the air to the saturated vapor pressure at the same temperature usually expressed as a percentage. Also the number of pounds of water carried by one pound of dry air.

  • Resistance

    The property of opposing the flow of electric current.

  • Return

    The warm water returned to top of cooling tower.

  • Reverse Osmosis

    The reverse flow of water through a membrane by applying pressure to overcome osmotic pressure.

  • Rinse

    Step in regeneration of an ion exchanger.

  • Riser

    The vertical section of piping that carries hot water to the top of the cooling tower.

  • RO

    Abbreviation for reverse osmosis.

  • Ryznar Stability Index

    An index to determine the scaling and corrosion tendencies of water.

  • SAC

    Abbreviation for strongly acidic cation resin.

  • Salinity

    The presence of soluble minerals in water.

  • Saponification

    The hydrolysis of a fat or alkali.

  • Saturated

    The maximum amount of a substance that can be put into the solution.

  • Saturated Steam

    Steam that is saturated with heat at a particular temperature and pressure.

  • SBA

    Abbreviation for strongly basic anion resin.

  • Scale

    A hard adherent, crystalline layer or layers. By analysis usually contains well over 50% of calcium and magnesium.

  • Scale Inhibitor

    Term broadly used when referring to any treatment that reacts with calcium or magnesium ions preventing them from depositing as scale.

  • Sedimentation

    Gravitational settling of solid particles in a liquid.

  • Sensible Heat

    Heat you can feel. Heat required to change the temperature of air or water.

  • Sequential

    One action occurring followed by others in a given order.

  • Sequestrant

    Term used that describes any chemical that forms a stable, water soluble complex.

  • Sessile

    Permanently fixed or unable to move.

  • Settleable Matter

    Matter that will settle out of solution by gravity under low flow conditions.

  • Shock Feed

    Introduction of a large quantity of chemical treatment into system water within a very short period of time. Term usually used to describe feed of biocide into tower cooling system.

  • Shot Feed

    Chemical feed system in which water flow, from high to low pressure side, forces chemicals from a feed tank into the system.

  • Sight Glass

    Glass tube mounted on outside of boiler indicating the water level within the boiler.

  • Silica

    Element found in water.

  • SIO2

    Chemical symbol for silica.

  • Skimmer


  • Slats

    Thin strips of wood or plastic suspended from frames inside cooling tower.

  • Slime

    A soft, sticky mucus-like substance originating from bacterial growth.

  • Slimicide

    Another term for biocide.

  • Sludge

    Matter in solution or matter that collects at the bottom of boiler drum.

  • Sludge Conditioner

    Natural or synthetic treatment that aids in preventing coagulation of system water particulates into a large floc or mass.

  • Slug Feed

    See SHOT FEED.

  • SO3

    Chemical symbol for sulfite.

  • Sodium Chromate

    Filming type corrosion inhibitor

  • Sodium Silicate

    Anodic corrosion inhibitor that hydrolyzes in water to form negatively charged colloidal particles which migrate to anodic site of corrosion cell.

  • Sodium Sulfate

    By product of reaction between sodium sulfite and dissolved oxygen.

  • Sodium Sulfite

    Treatment used to aid in reducing dissolved oxygen in steam boiler system.

  • Soft Water

    Water that contains little or no calcium or magnesium.

  • Softener

    External treatment process in which calcium and magnesium (hardness) are removed and replaced with sodium by cation exchange.

  • Solubilizing Program

    A deposit control program in which deposit forming cations are complexed (tied up), held in solution and dispersed in colloidal form in system water.

  • Soluble Oil

    Anodic inhibitor that forms negatively charged particles which migrate to anode of corrosion cell and precipitate, with metal ions, onto the anode site.

  • Soy Amine

    An acceptable food grade FILMING AMINE.

  • Specific Gravity

    The ratio of the weight of a given volume of a substance to the weight of an equal volume of water at a fixed temperature.

  • Specific Resistance

    The resistance between opposite faces of a one centimeter cube of a given substance and expressed in ohm-cm3.

  • Splash Packing

    Type of cooling tower fill consisting of slats so arranged that water falling through the tower is broken up into small droplets thus achieving better contact with air.

  • Spore

    A cell in a resistant envelope, capable of developing into a normal organism.

  • Spray Filled Tower

    Cooling tower in which breakup of water is dependent solely on spray nozzles.

  • Spray Pond

    System in which hot water in a cooling tower is pumped to a large pond or small lake, sprayed into the atmosphere through nozzles, and cooled by natural evaporation.

  • SRB


  • SS

    Chemical symbol for suspended solids.

  • Stability Index


  • Stable Water

    Water which is neither scale forming nor corrosive.

  • Stage Heater

    Device for heating feedwater.

  • Stand By

    Period during which system or equipment serves as a “back up”.

  • Static

    An ion exchange reaction occurring with a volume of liquid in contact with a volume of resin.

  • Steam Boiler

    Any device for the production of steam under pressure.

  • Steam Drum

    The upper boiler drum where steam is produced and withdrawn.

  • Steam Generator


  • Steam Header

    Large pipe, usually located on top of steam drum, through which steam exits a boiler.

  • Steam Purity

    Measurement which expresses the amount of contamination, either organic or inorganic, contained in steam.

  • Steam Quality

    The ratio of the weight of vapor to total weight of the steam water mixture.

  • Steam Trap

    A device for bleeding condensate out of a steam line without allowing steam to escape.

  • Stoichiometric

    Chemical reaction that results in a change in chemical solution.

  • Strainer

    A screen to remove matter that would otherwise cause plugging or deposits.

  • Substoichiometric

    1 to 1 ratio reaction. See STOICHIOMETRIC.

  • Sulfatereducing Bacteria

    Bacteria which assimilate oxygen from sulfate compounds, reducing to sulfide.

  • Sulfite Test

    Daily test performed on boiler system water to determine the amount of sodium sulfite present. Results expressed in ppm. When sulfite residual is within prescribed range-usually 20ppm-60ppm, it is assumed no dissolved oxygen is present and therefore, ‘pitting’ type corrosion is under control.

  • Sump

    See BASIN.

  • Super Critical Boiler

    Boiler operating at a pressure higher than the critical pressure, 3203.6 psig.

  • Super Heat

    The number of degrees Fahrenheit of steam above the temperature of saturated steam at some specified pressure.

  • Super Heater

    Tubes within a boiler through which saturated steam passes after leaving a boiler and where steam absorbs additional heat.

  • Super Saturated

    To contain more in solution than normal for a given temperature.

  • Supply

    Cooled water flowing from the basin or sump of a cooling tower.

  • Support Media

    A graded particle size, high density material such as gravel, anthrafil, quartz, etc. used to support the resin bed.

  • Surface Blowdown


  • Surface Tension

    The resultant attractive forces on molecules at the surface of a liquid, exerted by molecules within the liquid, that tends to make the surface contact to the smallest possible area.

  • Surface Water

    Water which has a short contact with the earth’s surface collecting in streams, rivers, lakes and reservoirs.

  • Surfactant

    Chemical that alters the surface and interfacial tension.

  • Surging

    See PRIMING.

  • Suspended Matter

    1. Finely dispersed particles of impurities of water, including industrial waste, silt, and organic substances. 2. Mineral salts (hardness) that has precipitated out of solution due to the heat or other influences.

  • Symbosis

    Relationship between a microorganism and a host that is beneficial to both.

  • Synergism

    1. A cooperative effort between two or more species of bacteria resulting in something the individual species could not accomplish alone. 2. Blending together of two or more chemicals so that the total effect is greater than the sum of the single effect taken separately.

  • TDS

    Chemical symbol for total dissolved solids. See TOTAL DISSOLVED SOLIDS.

  • TH

    Chemical symbol for total hardness.

  • Threshold Treatment

    Control of scale type deposits by feeding of a sub-stoichiometric dosage of treatment to system water.

  • Titrate

    Determining the amount of a substance in solution by adding a measured amount of another substance to produce a desired reaction or end point.

  • TOC

    Total Organics Carbon is the amount of carbon bound in an organic compound and is often used as a non-specific indicator of water quality or cleanliness of pharmaceutical manufacturing equipment.

  • Ton

    Term used to express capacity or size of a cooling system. Equal to 15,000 Btu per hour.

  • Tonnage

    Term used to indicate rated capacity of cooling system.

  • Total Chlorine Residual

    Total amount of chlorine present, without regard to type.

  • Total Dissolved Solids

    Term indicating the total amount of dissolved solids present in a water sample. Usually expressed as TDS in parts per million.

  • Tower


  • Tower Circulation Pump

    Pump that recirculates water to and from the cooling tower.

  • Tower Fill

    Tower which contains baffling inside used to increase break-up of water falling through tower into small droplets or sheets, and also to provide additional wetted surface.

  • Trichlorophenates

    Non-oxidizing microbiocide.

  • TS

    Chemical symbol for total solids.

  • TSS

    Chemical symbol for total suspended solids.

  • Tube

    A hollow metal cylinder to convey liquids or gases.

  • Tube Sheet

    Area in boiler or heat exchanger to which tubes are affixed or fabricated.

  • Tuberculation

    A hard, dense, scab-like deposit of metal oxide on metal surface.

  • Turbidity

    A suspension of very fine colloidal size particulates that obscures light rays, but requires many days of sedimentation due to the small particulate size.

  • Turbine

    Rotary device, powered by boiler steam, whose function is to drive some other rotating piece of equipment.

  • Turnover

    The mixing of lower and upper layers in a lake in spring and fall. Caused by temperature and density equalization.


    Abbreviation for micromho.

  • Underdeposit Corrosion

    Corrosion that takes place under any type of deposit due to the differential aeration or temperature.

  • Uniform Corrosion


  • Uniform Thinning

    Type corrosion in which metal is uniformly removed and thinned. Generally associated with metal exposed to low pH or acid solution.

  • USDA

    United States Department of Agriculture.

  • Valance

    The number of positive or negative charges on an ion.

  • Volatile Amine

    Treatment used to aid in control of corrosion in condensate system of boiler.

  • WAC

    Stands for weak acid cation resin.

  • Wall Tube

    Tube containing boiler water that shields refractory furnace walls by absorbing heat.

  • Water Formed Deposit

    Any accumulation of insoluble material derived from water or formed by the reaction of water upon surfaces in contact with water, i.e., scale, sludge, corrosion by-products or biological deposits.

  • Water Tube Boiler

    Boiler in which water is on the inside of the boiler tubes and flame and gases are on the outside.

  • Wet Bulb Temperature

    Temperature of saturated air.

  • Wet Layup

    Period during which system or equipment is non-operational and left full of water.

  • Zeolite

    A mineral composed of hydrated silicates of aluminum and sodium or calcium.

  • Zeolite Softener

    A term loosely used to designate a sodium regenerated ion exchange softener.

  • Zinc

    A non-ferrous metal.