The Pool & Spa Glossary contains much of the jargon and terms used in the swimming pool and spa/hot tub industry.  The explanations should allow you to better understand pool, spa and hot tub care instructions, trouble-shooting guides and the workings of your pool, spa or hot tub.  Helps you deal with water quality, water chemistry, sanitizing and related maintenance problems.  All of the listings, in bold, underlined type, are linked to a Manufacturer's Preview Page, which provides access to additional information and their corporate website.

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Acid:  a chemical that is used to lower the pH and/or total alkalinity.  Most commonly used are liquid muriatic acid (hydrochloric acid) or granular pH decreaser (sodium bisulfate). 

Acid Demand:  the amount of acid required to lower the pH into the 7.2-7.6 range.  Usually performed as a dealer test. if there are problems with high pH water conditions.

Acid Washing:  masonry pools are periodically acid washed, in order to remove stains, discoloration and improve their appearance.  Muriatic acid is commonly used for this purpose.  Typically, this messy task is left for a professional.  Additives that can help with the task are available.

Aggregates:  particles such as marble dust, crushed quartz, pebbles, stones or ceramics that are used as constituents in various pool plastering materials.  The look of the finished pool surface reflects the type of aggregate used, as well as the application techniques.

Alarms:  several types of alarm devices are used to promote pool safety and or/backyard safety.  Pool Alarm Systems can be used to detect intrusion into the pool and/or immediate environs and sound a siren or signal a remote sensor.  Gate Alarms Systems are used to signal the opening a yard gate.

Algae:  a single-celled plant, that can be present in a variety of colors.  Of the thousands of varieties, the most common in pools are:  blue-green, yellow mustard or black.   "Pink" algae is actually a bacteria and is usually present as a slime.   Algae can form in spots or over broad areas.  Low sanitizer levels are conducive towards algae growth.

Algaecide:  a chemical that kills algae.  Commonly available in a variety of chemical types:   quaternary ammonium compounds, copper, silver or polymer (poly quat).  Chlorine and bromine, also, function as algaecides.  The different types show varying effectiveness against different strains of algae.

Algaestat:  a chemical that inhibits or retards algae growth, but does not necessarily kill the algae.

Algal:   adjective form of the word algae.  Algal growth:  growth of algae.

Alkaline:  the opposite of acidic.  Alkaline materials have pH levels above 7.0 (neutral).   Synonymous with the word basic.

Alkalinity, Total (TA):  refer to the listing for Total Alkalinity (TA).

Alternative Sanitizers:  a group of products that sanitize pool, spa and hot tub water, by means other than the application of chemicals to the water. Includes such products as:  salt chlorine generators, ultraviolet sanitizing systems, mineral sanitizers, ionizers and ozone generators (ozonators). 

Alum:  a chemical (aluminum sulfate) used to clarify water, by creating a gelatinous precipitate, that has to be vacuumed to waste.  Technique is called flocculation.

Ammonium Sulfate:  the active ingredient in some types of yellow treatments.  Requires an initial shock treatment which converts to a high level of chloramines.  Under proper conditions, very high chloramine levels can aid in control of mustard algae.  Once under control, additional shock treatment is necessary, in order to destroy the chloramines and establish a suitable level of free chlorine.

Anion:  a negatively charged ion.  A negatively charged ion is anionic.  A positively charge ion is cationic.

Anti-Entrapment Safety Drain Covers:  a drain cover designed to prevent the snaring of swimmer's long hair or holding a swimmer underwater, due to the strong suction creating at the drain.  Products, such as this, are used to comply with the provisions of the Virginia Graeme Bake Act and various state laws.

Ascorbic Acid:  vitamin "C."  Can be used as an acidic reducing agent in the removal of difficult metallic stains from underwater surfaces.  Oxalic acid can be used in a similar manner.

Automation, Pool:  the use of a device to automatically control such as aspects of pool operation as:  filtering, chemical additions, sanitizer additions, heating, cleaning, covering, pool water level, underwater pool lighting, area lighting, monitoring, pool alarms, gate alarms and  pool security.

Backwash:  the reversing of the flow of water through the filter and sending it to waste.  This procedure will thoroughly flush the filter, media and components.  Follow the manufacturer's instructions!  Not all filters are routinely backwashed.  Sand filters should not be backwashed excessively:  pay attention to the pressure gauge and vacuum whenever conditions indicate the need.

Bacteria:  single-celled, microorganisms.  Can vary from harmless to pathogenic and include such types as E. Coli and pseudomonas aeruginosa.  Bacterial growth is the direct result of inadequate sanitation and is affected by such factors as bather load, pool or spa cleanliness, water temperature, water chemistry and filtration.

Bacterial:   adjective form of the word bacteria.  Bacterial growth:  growth of bacteria.

Bactericide:   a chemical that kills bacteria.  The most common bactericides are:  chlorine, bromine, biguanide, ozone and silver.  Most algaecides, other than copper, exhibit some bactericidal properties.

Bacterium:  singular form of the word bacteria.

Balanced Water:  pool or spa water that is within the accepted water analysis parameters for: pH, sanitizer, total alkalinity, calcium hardness, chlorine stabilizer (chlorine pools only) and minerals.  The balancing, of the pool or spa water, helps to eliminate water chemistry problems.

Base Demand:   the amount of pH increaser needed to raise the pH into the 7.2-7.6 range.   Usually performed as a dealer test, if there is a problem with low pH water conditions.

Basic:   the opposite of acidic.  Basic materials have pH levels above 7.0 (neutral).   Synonymous with the word alkaline.

Biguanide:  the generic name for a non-chlorine, non-bromine, sanitizer that utilizes the polymer PHMB (polyhexamethylene biguanide).  It is used to totally eliminate the use of chlorine or bromine.  A popular non-halogen, alternative pool, spa or hot tub chemical sanitizer.  Chlorine, bromine or non-chlorine shock will destroy the biguanide polymer.  Click here for some ordering information about Biguanide Test Kits.

Biofilm:   a slippery coating of microorganisms that can develop in poorly sanitized pools and spas.

Biodegrade:   the natural process by which organic substances break down or decompose into harmless basic materials:  water, carbon dioxide, nitrogen, etc.

Borates: refer to the listing for sodium tetraborate.

Breakpoint Chlorination:  the amount of chlorine required to completely oxidize all of the organic materials and decompose all of the combined chlorine present in the pool or spa water.  An amount of chlorine, 5-10 times the combined chlorine level, is typically required.

Broadcast:   the application of dry, granular chemicals to a swimming pool, by means of throwing or dispersing across the surface.  This allows for a "more gentle" addition of the chemicals to the water and avoids concentration or clumping.

Brominator:   feeding devices used to introduce bromine into pools or spas. Most automatic types can be plumbed inline.  Others are simple floating varieties.  All are intended to make the application of bromine easier and more consistent.  Do not use chlorine in place of bromine, in any brominator.

Bromine:  closely related to chlorine in chemistry.  It has become popular, especially in spas, because it has much less odor than does chlorine.  Available in solid forms for use in specialized bromine feeders or dispensers.  Also, available as a 2-part product for use in spas and hot tubs.

Buffer:  chemicals that help to stabilize the pH.  In pools and spas, sodium bicarbonate (baking soda) is typically used to create a buffer that helps keep the pH in the optimum range.

Bump:  a method by which the filter media, in certain types of diatomaceous earth (DE) filters, is repositioned or "bumped," in order to restore optimum filtering conditions.

Calcium Carbonate:   crystalline deposits (scale) that can form on all under water surfaces, if the water is excessively high in calcium hardness.  High pH and high total alkalinity can worsen the problem.  Responsible for cloudy water conditions that may result due to pool or spa water being out of balance.

Calcium Chloride:   a calcium compound that is used to raise the calcium hardness of the water.   Typically, available in a granular form for use in pools and a liquid form for use in spas and hot tubs.  Used to raise the calcium hardness level, of soft pool or spa water, into the 150-200 PPM range.

Calcium Hardness:   a measurement of the dissolved calcium content of the water.  Can be tested by various methods and is reported as PPM of calcium carbonate.  Proper pool or spa water balance usually requires that the calcium hardness of soft water be raised to 150-200 PPM.  Higher levels can lead to scaling or cloudy water problems and may require chemical treatment.

Calcium Hypochlorite:   most commonly used as a daily pool water sanitizer or shock treatment.  Typically contains 65-70% available chlorine and is available as a granular material.  Not completely soluble, high in pH and increases the calcium hardness with every application.  Use in hard water conditions may cause cloudy, hazy water or scaling problems to develop.

Carbon Dioxide:  a naturally occurring gas.   Can be used, in an automated system, to help lower and control the pH, without the use or corrosive acids.

Cartridge Filter:   a type of filter that utilizes a porous, pleated component or bag to remove particles.

Cation:  a positively charged ion.  A positively charge ion is cationic.  A negatively charged ion is anionic.

CH:  an abbreviation for Calcium Hardness.  Refer to that listing.

Check Cracks:   fine hairline cracks that can develop in plaster finished pools.

Chelating Agent:   a class of chemical compounds that reacts with minerals (heavy metals) such as iron, copper, manganese and calcium and forms stable, soluble products.  This action helps prevent staining and discoloration and is the preferred method for treating iron, copper and manganese.  When treating iron, manganese or copper, chelates should be added at a level at least equal to, if not greater than, the mineral being treated.  Chelation is a one molecule vs. one molecule process.  Adding more chelating agent is usually better than adding less.

Chloramines:  irritating, odorous forms of combined chlorine, formed by the reaction of chlorine with nitrogen containing waste products.  Ineffective as a pool or spa sanitizer.  High levels of chloramines can cause the problems of "Red Eyes" or "Stinging Eyes."   Usually requires a shock treatment to lower or destroy the combined chlorine level.

Chlorinators:  feeding devices used to introduce chlorine into pools and spas.  Most automatic types can be plumbed inline.  Others are simple floating varieties.  All are intended to make the application of chlorine easier and more consistent.  DO NOT USE BROMINE IN A CHLORINATOR - USE ONLY IN AN APPROVED BROMINE FEEDER.  Only solid trichlor products (tablets, sticks or other shapes) should be used in a chlorinator.

Chlorinators, Salt:  another term for Salt Chlorine Generator or Saltwater Chlorinator.  Refer to the listing for Chlorine Generator, Salt.

Chlorine, Available:  a somewhat archaic term for describing the chlorine level.  Sometimes used as "Free Available Chlorine" or "Total Available Chlorine."

Chlorine, Combined:   that form of chlorine that has reacted with nitrogen containing waste products.   Chloramines are the major constituent.  The combined chlorine should be no more than 1 PPM, ideally 0.3 PPM or less, as high levels can cause odor and irritation problems.

Chlorine Demand:   a measurement of the amount of Free Chlorine that must be added to water, showing a zero Free Chlorine level, in order to produce at least a minimally positive Free Chlorine level.  The test can be performed by some dealers.

Chlorine, Free:  the active, germicidal form, known chemically as hypochlorous acid.  This is the preferred form of chlorine sanitizer used in pools and spas.  Tested by DPD, Test Strips and Syringaldazine and reported as PPM.  A level of 1-3 PPM is considered ideal.  Higher levels can cause vinyl liner fading problems and bather irritation.

Chlorine Lock:  a somewhat archaic term used to describe the presence of high levels of combined chlorine.  Combined chlorine is the difference between the Total Chlorine reading and the Free Chlorine reading.  Ideally, it should be less that 1 PPM.  High combined chlorine content can result from the presence of nitrogen containing wastes such as urine and sweat.  Many people view any situation as chlorine lock, where lots of Chlorine has been added and there is little improvement in the chlorine readings.  This is not chlorine lock, but simply a case of needing to add more because of the pool's high demand for chlorine.  More algae and debris = more chlorine required!

Chlorine, Residual:  a somewhat archaic term for describing the chlorine level showing up on a test.

Chlorine Generator, Salt:   equipment that actually manufactures chlorine by converting salt into chlorine, as the water passes over specially-coated, titanium electrodes.  Plumbed in-line, these devices can provide normal chlorination, without the need to handle chlorine.  Pools using a chlorine generator should be maintained in the same manner as any other chlorine pool.  Also referred to as a Salt Chlorinator or as a Saltwater Chlorinator.

Chlorine Neutralizer:  a chemical used to quickly lower the chlorine level of a pool, spa or hot tub.  Typically, only in the case of a serious overdosing of the water.  It is always better to add product incrementally:  you can always add more - you can't take out!  Can be used with bromine as well.  Typically, sodium thiosulfate or sodium sulfite is used in this application.

Chlorine, Stabilized:  chlorinated cyanuric acids.  Available in two forms:  Trichlor, approximately 90% available chlorine and Sodium Dichlor, approximately 56% available chlorine.  Refer to those listings for more information.

Chlorine, Total:   the measurement of the total amount of FREE CHLORINE plus the amount of COMBINED CHLORINE.   Tested by OTO as well as the materials used to test for Free Chlorine.  Reported as PPM.  Test readings are always higher than the Free Chlorine readings.  The Total Chlorine level should not be more than 1 PPM higher than the Free Chlorine reading.  Ideally, a level of 0.3 PPM would be even better.

Circulation Booster:  a device installed in the return fittings to help improve sanitation, chemical distribution and heating, by improving water flow and eliminating dead zones.  Click here for some ordering information about The Circulator.

Clarifier:  a class of polymer based products that act on suspended, insoluble particles and organic debris and coagulate or clump them together, for easier and more efficient filtration.   Some particles, especially dead algae, might otherwise pass right through some filters.  Used in conjunction with proper pool or spa water chemistry and sanitizer levels, these products help produce sparkling, crystal clear water and help eliminate water clarity problems.

Colorimeter:  a type of water analyzer that uses an instrument with a precise light source and sensor to measure slight differences in color.  Also, referred to as a Photometer, these instruments are amongst the most reliable and accurate means of analyzing water.  Testers are available for all needs.  Totally eliminates the need to visually match colors, making it perfect for the color-vision impaired.

Cobalt Bleeding:  a problem is occasionally present in older fiberglass pools and spas and can cause a problem resulting in dark-black spots or blotches forming on underwater surfaces.  Stain removal treatments may prove useless or temporary.  The most practical remedy is to refinish the pool or spa.

Copper:  used as an active ingredient in some algaecides (chelated copper algaecides) and as a component in Ionizers and Mineral Sanitizers.  Copper sulfate should not be used as a swimming pool algaecide. Usually, copper is not found in most municipal water supplies.  High concentrations of copper, from natural sources, corrosion or copper sulfate, can result in colored stains and/or discolored water problems.  It is best treated with a product such as the METALTRAP Filter.  Click here for some ordering information about Copper Test Kits.

Conditioner, Chlorine:   cyanuric acid (cya) is used in outdoor swimming pools, as a chlorine stabilizing agent.  Helps protect chlorine from being destroyed by the Sun's UV (ultraviolet) rays.   Makes chlorine last longer.  Also called chlorine stabilizer.

Controllers:  pool automation devices that can be used to control aspects of water chemistry, filtration, heaters, pool safety covers, lighting, pool cleaning and more.  Usually timer controlled and programmable.

Corona Discharge:  a method for producing ozone, by utilizing high voltage arcing to convert oxygen (O2) into ozone (O3).  Refer to the listing for Ozone for more information.

Corrosion:  a potentially damaging condition that results from low pH (acidic) conditions.  Can cause damage to masonry surfaces and underwater metal parts.  Corrosive conditions will make chlorine more irritating and aggressive.  Proper pool or spa water chemistry or balancing helps prevent corrosion problems.

Covers, Pool Safety:  a type of cover that is installed on a track and can be rolled or unrolled, either manually or automatically.  Used for safety purposes and to reduce water and heat loss.

Covers, Solar:  a cover used to help increase or maintain the water temperature.  Typically, a plastic, bubble-filled material that floats on the pool surface.  Cannot be used for winterizing or safety purposes.

Covers, Winter: used to cover the pool for the winter months, after the pool has been properly prepared and winterizing chemicals have been added.  A variety of cover types are available:  mesh, laminate, solid.

Cryptosporidium:  an infectious microorganism (protozoa) that can be difficult to control, with chlorine and other common sanitizers, and cause infectious problems in pools and spas.  Ultraviolet (UV) sanitizers are particular effective, but must be used with other oxidizers/sanitizers.

CYA:  an abbreviation for Cyanuric Acid or Chlorine Conditioner/Stabilizer.  Refer to the Conditioner, Chlorine listing.

Cyanobacteria:  the scientific name for the most common variety of blue-green algae found in swimming pools.

Cyanuric Acid (CYA):  the active ingredient in chlorine conditioner/stabilizer.  Refer to Conditioner, Chlorine listing.

Diatomaceous Earth (D.E.):  a filter media that is used in D.E. Filters, in order to produce highly effective filtration.  D.E. can be used as a filter aid with sand or cartridge filters, in order to better deal with certain pool or spa  cloudy water problems or  conditions.

Degassing Unit:  a mixing chamber for ozone and water, that can be used to increase the efficiency of an ozonator.  By creating small bubbles of ozone, contact time and absorption is increased and the amount of ozone "gassing off" is decreased.

Delamination:  poorly preparing the surface of a gunite pool, prior to applying a finishing coat, can lead to poor adherence or delamination of the coating.  More common in refinished pools, this can lead to calcium nodules and other problems.

Desiccant Liner:  an added measure of moisture protection used in some brands of test strips for pools and spa use.  Much superior to the more common silica gel drying packets.

Dichlor, Sodium:  this type of stabilized chlorine is popular as a daily pool water or spa water sanitizer.  Typically contains 56-60% available chlorine and is available in a granular form.  It is quick dissolving and is essentially pH neutral.  Can be used as a shock treatment.  Contributes cyanuric acid to the water, each time product is added.

DPD:   one of the preferred methods to test for Free Chlorine.  Variations can be used to test for the other forms of chlorine.

Dry Acid:  sodium bisulfate.  A pH decreaser chemical that is used to lower the pH and total alkalinity.

Enzymes:  organic agents that hasten the natural breakdown (digestion) or decomposition of oily wastes and organic residues in pools and spas.

Epoxy Based Refinishing:  materials that are used to refinish and seal a masonry pool.  Offers the advantage of strength and durability and reduced interaction between the masonry products in the walls and the pool water chemistry.

Escherichia Coli (E. Coli):  a pathogenic, fecal bacteria.  Presence in pool or spa water at infectious levels may be the result of inadequate sanitation, gross contamination or poor water management.

Exposed Aggregate Finish:  a type of product that is used as the interior finish in some masonry pools.  Typically, a mixture of selected aggregates and Portland cement.   An acid etching is used to expose some of the aggregates, creating its textured, finished look

FAC:  an abbreviation for Free Available Chlorine.  Refer to the Free Chlorine listing.

Filter Media:  materials used to remove dirt and debris from water.  Common media include:  diatomaceous earth, sand and zeolites.  D.E is used only with specific filters.  Sand and zeolites are used, interchangeably, in all sand filters.

Floatation Tanks:  also known as floatation chambers, isolation tanks, sensory deprivation tanks, salt water spas and REST chambers.  Filled with a concentrated solution of Epsom salts, the user floats in splendid isolation, separated from the various stimuli of the surroundings.

Flocculation:  the process by which insoluble, fine particles are caused to precipitate from suspension.   Alum works by this principle.  However, other more modern polymer-type liquids or tablets accomplish the same net result, without having to generate large amounts of additional gelatinous precipitate.

Foam:  can result in pools that have used quaternary ammonium compound (QUATS) algaecides.  This can be made worse, if there is an air leak in the return line.  In spas, body oils can react with the natural alkalinity of the water and form "soaps".   Aeration will increase the foaming problem.  Anti-Foam products and enzyme products are useful in controlling the problem.

Folliculitis:  a rash-like bacterial infection of the hair follicles caused by inadequate sanitation of spa or hot tub water.  Caused by the same bacteria, pseudomonas aeruginosa, responsible for swimmer's ear and conjunctivitis.  Medical treatment should be sought in suspected cases.

French Drain:  a system intended to improve drainage around a pool or house foundation.  Usually consists of a perforated pipe surrounded by gravel in a trench.  The pipe has to slope away from the area to allow for drainage.  If this not possible, a sump pump might be required.

Gallon (US):  a unit of liquid volume, primarily used in the U.S.  One gallon (US) = 3.8 liters.  (Metric Conversions- click here)

GFI:  Ground Fault Interrupter.   A type of electrical safety receptacle that prevents the possibility of electrical shock in outdoor equipment or around water.  Usually, if not always, required by local or national codes.

Giardia:  an infectious microorganism (protozoa) that can be difficult to control, with chlorine and other common sanitizers, and cause infectious problems in pools and spas.  Ultraviolet (UV) sanitizers are particular effective, but must be used with other oxidizers/sanitizers.

Grains:  an alternative way of stating concentration.  One grain = 17 PPM.

Gunite:  a water, sand and cement mixture that is "gunned" onto the formed shape of a pool interior under construction.  After application the walls are troweled.   Finally, a layer of a "plaster" finish is applied over the gunite.   It is this "plaster" layer, most commonly a marble dust Marcite or an aggregate finish, that will actually contact the water and will be visible.

Halogens:  chlorine and bromine are members of the halogen family of elements.  As used, in swimming pools and spas, chlorine and bromine are referred to as halogen sanitizers.  All other sanitizers are non-halogen.

Hard Water:  the term used to describe water that is high in calcium or magnesium.  High levels, usually over 400 PPM, can lead to clarity and scaling problems, if not treated.   Source of the calcium can be natural or can be contributed by chemicals such as calcium hypochlorite.

Heat Pumps:  a type of heater that is similar to an air conditioner operating in reverse and extracts heat from the air..  Cost effective and clean to operate, heat pumps are suitable for summertime usage in the entire country and wintertime operation n the southern areas only.

Heaters, Solar:  a type of heater that utilizes the Sun's energy.  Solar heating systems can be plumbed into the pool's existing filtration system and can provide enough FREE energy to raise the water temperature by as much as 10ºF (6ºC).

Heavy Metals:  a term used to describe the presence of metallic elements such as iron, copper, manganese, etc.  Responsible for many types of problems involving staining and colored pool or spa water.  Click here for some ordering information about Heavy Metals Test Kits.

Hopper:  the deep end of an inground pool.

Hot Tub:   originally designed and manufactured along the line of a barrel, these products are an alternative to the typical spa.  Most are made of redwood or cedar and can have an internal vinyl liner to keep the water away from the wood.  Equipped with heaters, air jets and  filters, hot tubs provide relaxing baths, arthritis relief and enjoyment.  Sizes can vary.  The term "hot tub" is used, somewhat, interchangeably with the term "spa."

Hypochlorites:  a group of chlorine compounds used to sanitize or shock pool or spa water.  Includes:   liquid sodium hypochlorite, and granular calcium and lithium hypochlorites.

Hydrogen Peroxide:   H2O2, a concentrated solution of a powerful oxidizing agent.  Used as a shock treatment for pools and spas being maintained on biguanide and it situations where chlorine or bromine products cannot be used.  This product should not be confused with the hydrogen peroxide solutions that are used for household or personal uses, as this product is many times more concentrated.  Handle with appropriate caution!  Click here for some ordering information about Peroxide Test Strips.

Ice Compensator:   a flexible, crushable component that can be placed in the skimmers or floated on the pool surface, as part of the winterizing procedure.  Helps to protect against possible freeze-thaw damage.

Ions:  the electrically charged state that an element assumes in true solution.  In the ionic state, ions are chemically reactive.  Some ions, such as, copper, silver and zinc, are used as sanitizers in mineral sanitizers and ionizers.

Ionizers:  equipment that sanitizes pool and spa water by providing a low level source of copper and silver ions, as the water passes over charged electrodes.  Copper ions can provide algaecidal control.  Silver ions can provide bactericidal control.  Other types of devices (mineral purifiers) work by an erosion principle and utilize copper, silver or zinc ions.

Iron:  a mineral, which can occur naturally in water and can be especially high in well water.   Can lead to problems with staining and discoloration of the pool or spa water and underwater surfaces.  Requires treatment with chelating agents.  Best to treat prior to adding chlorine or raising the pH.  Testing of the water will determine the concentration in PPM and allow for an appropriate dosage of chelating agents to be added.  Any measurable amount of iron is capable of causing a problem, if not treated.  It is best treated with a product such as the METALTRAP Filter.  Click here for some ordering information about Iron Test Kits.

Kilogram:  metric unit for weight.  One kilogram = 2.2 pounds.  (Metric Conversions- click here)

Langelier Index (Saturation Index): a system for determining the scaling or corrosive tendencies of pool or spa water, by testing the pH, total alkalinity, calcium hardness and water temperature.  Each parameter is assigned a value, as per a chart, and is used to calculate the Index.   Ideal would be a value of -0.5 to +0.5.  Values outside of the range, indicate out of balance conditions and may require chemical treatment.  More negative values indicate corrosive conditions.  Higher positive values indicate scaling conditions.

Lanthanum:  a rare earth element.  Refer to the listing for Phosphate Eliminators for more information.

Leaching:  a term used to describe the movement of slowly soluble constituents, present in masonry pool finishes, into the pool water.  Overall water chemistry governs to what extent any leaching can occur.  Normally affects the parameters of pH, total alkalinity and calcium hardness.

Leak Detection:  the use of specialized equipment to locate the source of a pool or spa leak.  Usually performed by a professional leak detection service company.

Liter:  metric unit of volume.  One U.S. Gallon = 3.8 liters. (Metric Conversions- click here)

Lithium Hypochlorite:   most commonly used as a daily pool water sanitizer or shock treatment.  Typically contains 35% available chlorine and is available as a granular material.  Completely soluble and high in pH. Tends to raise the pH over time.  Contributes no problematic residues to the water.

Magnesium:  a naturally occurring mineral that is common in hard water. Shares a similar chemistry with that of calcium.  Tends to be more soluble than calcium, especially at pool or spa conditions.  Measured as part of total hardness.  Epsom salts are magnesium sulfate.  Not associated with any staining or discoloration problems.

Magnetizers, Pool & Spa Water:  magnetic devices that can be attached externally to the return lines.  It is reported that a pool or spa water magnetizer, also known as a magnetic water conditioner, helps reduce and eliminate scale formation and can have a positive impact on the sanitizer levels and the overall water chemistry.  Click here for some more product and ordering information about Magnetizers.

Main Drain, Anti-Vortex:  safety design features have been incorporated and regulations enacted to prevent the entrapment of swimmers in the powerful suction of main drains.  A ramped ring can be placed around the anti-vortex main drain, to help prevent pool cleaners from getting stuck in place.

Manganese:   a mineral that can occasionally occur in well water.  Even low concentrations can cause brown-black staining and discoloration problems.  High concentrations can prompt the use of an alternative water source.  Can be treated along similar lines to iron, in pool or spa water.  Not usually found in municipal water supplies.  It is best treated with a product such as the METALTRAP Filter.  Click here for some ordering information about Manganese Test Kits.

Marcite:  a finish for gunite pools that consists of crushed marble and white Portand cement, that forms a water tight layer over the underlying gunite.

Micro-filter:  a filter capable of removing very fine particles: even dead algae and bacteria.  Some Robotic Pool Cleaners feature a built-in micro-filter that works in conjunction with the pool filter to produce higher quality pool water.

Mineral Hybrid: a type of device that releases silver ions into the water at very low levels, for persistent sanitizing action and produces chlorine, by means of a salt chlorine generator, for oxidation and sanitizing.. 

Mineral Sanitizer: a type of device that releases some combination of copper, silver or zinc ions into the water at very low levels.  In this ionic state, these minerals can function in the sanitizer role and help control algae and bacteria in pool and spa water. Mineral Sanitizers work on the principle of erosion and do not require electrical components.  Most include some type of replaceable cartridge, that contains the copper, silver or zinc materials.

Minerals:  naturally occurring components of water.  Include:  salt, calcium, magnesium, iron, manganese, copper, etc.

Microorganisms:  include algae, bacteria, mold and fungus.  Control of microorganisms is the reason pool and spa water require continuous sanitizing with chemicals or methods such as chlorine, bromine, biguanide, algaecides, ozone, ionization, ultra-violet, etc.

Mottling:  a term used to describe dark blotches, spots or stains that can appear on some plastered pools.  This problem may be caused by the "use and abuse" of  calcium chloride in the plastering mixture.  Refer to Service Industry News:  issue 1/15/03.  There is no solution, short of refinishing, if this is the problem.  Algae and metal stains are other possibilities.

MPS:  monopersulfate shock.  Refer to the listing for non-chlorine shock.

Multi-Port Valve:  a valve with selectable positions that is associated with the filter.  Positions include:  filtering, backwashing, waste and bypass.

Muriatic Acid:  the common name for hydrochloric acid.  Used to lower pH, lower total alkalinity, acid washing and stain removal.

Nitrates:  a vital nutrient for algae that can stimulate growth and lead to higher consumption of chlorine.  The presence of nitrates in swimming pool water is undesirable. especially at levels above 10-25 PPM.  Nitrates can find their way into swimming pool water from:  well water contaminated by agricultural runoff, decaying plant matter, urine, sweat, fertilizers, acid rain, wind-blown matter, bird droppings and contamination with ground runoff.  While it is possible to remove nitrates with ion-exchange resins, it may not be a cost effective method.  Replacement of all or part of the pool water is the most common method of removal.  Click here for some ordering information about Nitrate Test Kits.

Nodules:  a white spot or bump, consisting of calcium carbonate, that has erupted at the surface of a plastered pool.  More common in refinished pools, it can be caused by poor surface preparation, voids or hairline cracks.  Can occur a few times before ceasing and, generally, requires sanding of the surface.

Non-Chlorine Shock (MPS):  typically potassium monopersulfate.  Also known as monopersulfate compound and potassium peroxymonosulfate.  Replaces or assists chlorine in destroying organic contamination and chloramines. Used as a shock treatment, it is completely soluble, chlorine-free, quick acting and does not create a build-up problem.  Click here for some ordering information about MPS Test Strips.

Opening:  start-up steps taken to restore the pool to operational status.

ORP (Oxidation Reduction Potential):  a measurement of the state of the oxidizing power of pool water containing chlorine or bromine.  Requires the use of a electronic meter and special electrodes, a minimum of 650 MV (millivolts) is considered ideal,  Pool or spa that has the recommended levels of free chlorine or bromine and the optimum pH, should have an acceptable ORP.  As the pH falls, the ORP rises, making reliance of this test alone a somewhat impractical matter.  It is useful as a supplement to the standard  water analysis tests.  Click here for some ordering information about ORP PockeTesters.

OTO:  ortho-tolidine.   A solution used to test for total chlorine only.  Other products should be used to test for Free Chlorine:  the active germicidal form of chlorine.

Oxalic Acid:  can be used as an acidic reducing agent in the removal of difficult metallic stains from underwater surfaces.  Ascorbic acid can be used in a similar manner.

Oxidation:  the chemical reaction by which organic matter is burned or destroyed, by the action of chlorine, bromine, ozone, hydrogen peroxide or non-chlorine shock.   Oxidation may cause minerals such as iron, manganese and copper to form discoloring stains and precipitates, if not treated properly.

Oxidation Reduction Potential (ORP):  refer to the listing for ORP.

Ozonator:   a device for producing Ozone (O3), by either a UV (ultraviolet) light source or by electrical arcing (corona discharge).  Also referred to as Ozone Generators.  Used for oxidizing and sanitizing purposes in both pools and spas.  Click here for some ordering information about Ozone Test Kits.

Ozone (O3):  typically produced by an Ozonator installed in a pool or spa.  Ozone (O3) is a form of oxygen (O2) and is a powerful oxidizing agent. It is used to destroy organic waste and byproducts and help in the control of algae and bacteria.  Not a stand-alone sanitizer:  needs some supplementing with chlorine, bromine or ionization.  Click here for some ordering information about Ozone Test Kits.

Parameter:   limits, ranges or boundary-determining characteristics.  The common water analysis parameters include:  pH, total alkalinity, chlorine or bromine, calcium hardness, chlorine stabilizer, iron, copper, TDS, etc.  The control and adjustment of these various parameters is referred to as water balancing.

Pathogenic:   a term used to describe infectious, disease-causing microorganisms such as e. coli or pseudomonas aeruginosa.  These bacteria can cause infectious conditions, if improper sanitation allows their presence to expand beyond certain threshold populations. 

pH:  the pH scale goes from 0 to 14.  0 is the most acidic.  14 is the most alkaline.  7 is neutral.  The ideal range for most pools and spas is 7.2-7.8.  This is a compromise of several factors:  allows for reasonable effectiveness of chlorine or bromine, bather comfort, corrosion and scaling considerations and the solubility of dissolved minerals.  pH values less than ideal can lead to corrosion problems.  Values higher than ideal can lead to cloudy water and scale formation.  pH is an important parameter and must be controlled.  Chemicals are available to lower or raise the pH.  Control of total alkalinity aids in stabilizing the pH.  Click here for some ordering information about pH PockeTesters.

Phenol Red:  the material that is most commonly used to test the pH of pool or spa water.

Phosphate Eliminators:  based on the chemistry of the rare earth element Lanthanum.  Lanthanum compounds have been found to help remove phosphates from the water.  When used, as directed, lanthanum compounds can lower the phosphate level to just parts per billion.  This almost total depletion of a vital algae nutrient helps prevent or retard algae growth, so long as the overall pool sanitizing and chemistry are maintained.

Phosphates:  a vital nutrient fort algae growth.  Can be introduced into pool water by decomposition of vegetation, urine, body wastes, agricultural runoff and some mineral or scale treatments.  High levels can promote algae growth.  The use of a phosphate eliminator can reduce the level to close to well below 1 PPM.  Click here for some ordering information about Phosphate Test Kits.

Photometer:  a type of water analyzer that uses an instrument with a precise light source and sensor to measure slight differences in color.  Also, referred to as a Colorimeter, these instruments are amongst the most reliable and accurate means of analyzing water.  Testers are available for all needs.  Totally eliminates the need to visually match colors, making it perfect for the color-vision impaired.

Plaster:  a type of finish that is applied over the concrete shell of inground pools.  Typically, a mixture of marble dust and Portland cement.

Polymucosaccharide:  the outermost surface or layer of black algae and other resistant types.  This polymucosaccharide layer can act as a water repellent barrier and shield the underlying algae from contact with the chemically-treated water.   Refer to the listing for Wetting Agent for more information.

Pool, Above-Ground:  a type of home pool that is built on top of the ground.  This type of pool can be constructed of various materials and contains a vinyl liner to contain the water.  Pool size can vary from very small to large.

Pool, Inground, Fiberglass:  a type of pool that is built into the ground, with fiberglass as the material of construction.    Not very flexible in terms of size and shape.

Pool, Inground, Gunite:  a type of pool that is built into the ground, usually level with the surface.  This type of pool can be constructed with a concrete shell (gunned on: hence the name gunite).  The surface can be finished with a variety of  plaster or aggregate materials.  Very flexible in terms of size and shape.

Pool, Inground, Vinyl:  a type of pool that is built into the ground, usually level with the surface.  This type of pool can be constructed of a variety of structural materials:  aluminum, steel, polymer plastic and wood.  This type of pool utilizes  a vinyl liner.  Very flexible in terms of size and shape.

Pool Cleaners (Vacuums), Automatic:  devices, which vacuum or remove dirt and debris from the pool bottom or walls.  Many devices can be attached directly to the skimmer and will randomly traverse the pool.  Other equipment requires a separate pump.  Robotic Pool Cleaners operate on low-voltage electricity, require no installation and are programmed to clean walls, bottoms and water line areas..  Some models can be used in conjunction with ozonation.  Automatic cleaners help improve the circulation of water, on the bottom, and are an aid in avoiding algae blooms.

Potassium Monopersulfate:  a chemical name for Non-Chlorine Shock.  Refer to that listing.

Polymer Algaecide (polyquat):  a type of algaecidal ingredient that is based on a polymer (a long chained, repeating molecule).  The algaecides based on this ingredient have become known as "poly quats" and are amongst the most effective algae control products.

Pound:  a unit of weight measurement primarily used in the U.S.  One pound = 0.454 kilograms.  (Metric Conversions- click here)

PPB:  parts per billion.  Used as a unit or measurement of concentration, for most phosphate testing.  1 PPM equals 1000 PPB.   pH is the only common pool parameter not expressed as PPM. 

PPM:  parts per million.  Used as a unit or measurement of concentration, for most common pool water parameters and chemicals.  1 PPM equals 1 pound per 1 million pounds of water.   pH is the only common pool parameter not expressed as PPM.  Occasionally, concentration is expressed in grains:  1 grain = 17 PPM.

Precipitation:  the formation of an insoluble chemical compound, thereby, causing it to drop out of solution.   Changes in the water analysis parameters of pH, total alkalinity and calcium hardness can cause precipitation.  Not treating dissolved minerals such as iron, can lead to precipitation, that can result in staining and discoloration problems.  Precipitation of calcium can lead to cloudy/hazy pool or spa water or scale deposit problems on the underwater surfaces..

Pseudomonas Aeruginosa:  an infectious, pathogenic bacteria.  Inadequate sanitation, gross contamination or poor water management can foster the growth of this bacterium, causing swimmer's ear, conjunctivitis or folliculitis.  Treatment should include proper medical services.

Quartz:  a commonly used ingredient in quartz-aggregate finishes.  Quartz or silicon dioxide is more chemical resistant and durable than the more traditional marble dust additives.

Quaternary Ammonium Compounds (quats):   a type of algaecidal ingredient, used to treat the most common varieties of algae.   Typically present as dimethyl benzyl ammonium chloride or a variation.  Can act as a wetting agent to help improve the effectiveness of other sanitizers.   Drawback is the tendency to cause foaming problems.

Reagent:  the chemist's technical term for a testing solution.

Robotic Pool Cleaner:  a type of highly featured pool cleaner that can be programmed to suit a pool's requirements.  Contains a self-contained, washable micro-filter bag that can remove fine particles, dead algae and even bacteria.  It is like having a second moving filter.

Saltwater Chlorinator:  another term for Salt Chlorinator or Saltwater Chlorination.  Refer to the listing for Chlorine Generator, Salt.

Sand Filter:  a tank-shaped filter that utilizes a special grade of sand, as a filter media.  Not always the most effective:  benefits from periodic use of water clarifying products.   Common mistake is backwashing too often.  The efficiency of a sand filter can be significantly improved by using a zeolite sand filter replacement media, in place of the filter sand.

Sanitizers:  chemicals or equipment used to kill bacteria, viruses, algae and mold.  Include:  chlorine, bromine, biguanide, ozone generators or ozonators, ionization, mineral sanitizers, salt chlorine generators, ultraviolet (UV) sanitizing, etc.

Saturation Index:  another name for the Langelier Index.  Refer to that listing.

Scale Formation:  caused when the levels of dissolved calcium carbonate reach the maximum, based upon the actual water chemistry.  Scale (calcium carbonate precipitate) shows up as a whitish coating on the underwater surfaces.  If left untreated, it can cause problems with filtration and pool heating.  Scale can occur, if the calcium hardness exceeds 400 PPM and the pool chemistry is not properly maintained.  Scale can be controlled by lowering the calcium hardness level, adding Scale Control Chemicals (sequestering or chelating agents), lowering the pH towards 7.2 and lowering the total alkalinity towards 80 PPM.  Pools, with scale-forming potential, should avoid the further use of products such as calcium hypochlorite:  a source of calcium.  The use a Magnetic Water Conditioner can offer help in dealing with scale formation.

Sequestering Agent:  a class of chemical compounds that form a loose association with dissolved minerals such as calcium or magnesium.  These chemicals help keep the minerals in solution, prevent scale formation and, over time, redissolve scale deposits.  Sequestering is the preferred way to treat calcium problems.  Click here for some ordering information Sequestering Agent Test Kits.

Shock:  refers to the application of large quantities of chlorine (superchlorination), non-chlorine shock or hydrogen peroxide.  Typically 5-10 times the normal dose is used, based upon actual conditions and needs.  The purpose of this large dose is to break down (breakpoint chlorination, in the case of chlorine) the combined chlorine, organic waste and contamination and re-establish a positive level of Free Chlorine.  Shocking must be repeated, until such time as a stable Free Chlorine reading can be achieved, for at least a few hours.  Make sure that a Free Chlorine capable test kit is being used, in order to know when breakpoint chlorination has been achieved.

Silt:  ultra fine particles that settle to the bottom, during periods of inactivity.  The action of the bathers tends to lift the silt up off the bottom, detracting from the water clarity.  Vacuuming before the pool is used or the use of a automatic or robotic pool cleaner can help control the problem.

Silver:  used in Ionization units and mineral sanitizers.  Silver ions can function as a bactericide.

Skimmer:  the water-level device, in the pool wall, that aids in the removal of floating debris and serves as a filter intake.

Slime:  is usually indicative of the presence of an algal or bacterial film and is likely due to inadequate sanitation and/or water circulation.

Soda Ash:  sodium carbonate.  The chemical used to raise the pH of water. Neutralizes acid.   Not the same chemical as sodium bicarbonate, sodium hydrogen carbonate or baking soda,

Sodium Bicarbonate:  sodium acid carbonate, sodium hydrogen carbonate, baking soda.  The chemical used to raise the total alkalinity of the water. Creates a buffer and helps stabilize the pH in the ideal range.  Not the same chemical as sodium carbonate or soda ash.

Sodium Bromate:  a suspected hazardous chemical that was found in trace amounts in pools that were using a salt bromination system.  This let to the recall of these units in 2002, while the subject was investigated further.

Sodium Bromide:  converts into active bromine sanitizer, when oxidized by the action of chlorine or non chlorine, monopersulfate shock.  Typically, used to treat a variety of resistant or problematic conditions such as "pink" algae, water mold, slimes and yellow-mustard algae.

Sodium Carbonate:  refer to soda ash listing.

Sodium Bisulfate:  available as a pH reducer, this acidic, granular chemical is used to lower the pH and/or total alkalinity.  Neutralizes the effects of high pH chemicals.  Also known as sodium hydrogen sulfate.  Concentrated solutions are very acidic!

Sodium Dichlor:  a form of stabilized chlorine.  This chlorinated cyanuric acid is completely soluble and is essentially pH neutral.  Used for routine daily sanitizing and shocking (superchlorination) in pools and spas.  Typically, 56% available chlorine.

Sodium Hydroxide:  a caustic, high pH by-product produced by the most common types of salt chlorine generators.  Neutralized as part of the routine maintenance of the pH, presenting no handling hazards.  Also known as lye or caustic soda.

Sodium Hypochlorite:  liquid solution of chlorine.  Typically 10-15% available chlorine.  High pH material.   Regular additions will require applications of acid, in order to maintain the proper pH.

Sodium Tetraborate:  is the basis of a chemical treatment program that helps to reduce the amount of dissolved carbon dioxide gas in the water.  This reduction makes it more difficult for algae to thrive and allows for reduced chlorine levels, without compromising effectiveness.  Click here for some ordering information about Borate Test Strips.

Soft Water:  is water that is low in calcium and magnesium hardness.  Such water can prove to be corrosive to masonry surfaces and underwater metal parts.  The calcium hardness level can be raised, to the optimum range of 150-200 PPM, by the addition of appropriate amounts of a calcium hardness increaser (calcium chloride).  Vinyl pools can be maintained at a lower level: 80-200 PPM.

Solar Blanket:  a translucent floatable blanket that is placed directly on the pool's surface.  Warms the water by reducing evaporation (a cooling process) and utilizing the Sun's rays passing through the blanket.  Usually made from an air bubble filled plastic sheet.

Solar Heating Systems:  a type of heater that utilizes the Sun's energy and can be plumbed into the pool's existing filtration system:  providing enough FREE energy to raise the water temperature by as much as 10ºF (6ºC).

Spa:  a popular form of aquatic recreation.  Available in a range of sizes and shapes, these products are used for relaxing bathing, arthritis relief and fun!  Portable, ready to plug in and inground, built-in variations are available.  Units feature heated water, air jets and massage therapy.  Hot tubs are a design variation, usually of wooden construction.  The phrase "hot tub" is sometimes used interchangeably with that of the term "spa."

Stabilizer, Chlorine:  cyanuric acid.  Also known as chlorine conditioner.  Refer to listing on chlorine conditioner.

Swale:  use of ground contours to direct water drainage or flow.

Strip Reader, Water Analyzer:  a type of water analysis that use scanning technology to read the colors on a test strip.  This type of equipment is unlikely to provide and degree of reliability beyond that of the test strips being used.  Test strips are a convenient testing method, but do not provide the accuracy of a modern testing lab.

Sulfur:  a naturally occurring mineral, that can be found in some poor quality well water.  Produces odorous and potentially irritating conditions.  The PURESTART Pre-Filter is a cartridge like device that simply attaches to a garden hose.  It can remove sulfur from pool water and from all new water additions.

Superchlorination:  is basically another term for "shocking".  Refer to the listing on Shock.

Syringaldazine:  the chemical used in most test strips to perform all of the Chlorine and Bromine tests.  This is the most reliable method to use, especially in the presence of higher levels of Free Chlorine.

TA:  an abbreviation for Total Alkalinity.  Refer to that listing.

TAC:  an abbreviation for Total Available Chlorine.  Refer to the Total Chlorine listing.

TDS:  an abbreviation for Total Dissolved Solids.  Refer to that listing.

Test Strips: relatively, modern methods of testing pool and spa water.  Typically, able to do a variety of tests including:  Free Chlorine, Total Chlorine, Bromine, pH, Total Alkalinity, Calcium Hardness, Chlorine Stabilizer, etc.  Not all strips do all tests.   A convenient, no chemicals way to test water.  Click here for some ordering information.

Titanium:  an ultra-strong, corrosion-resistant metal that is used in electrodes for salt chlorinators and other alternative sanitizing devices and as a copper alternative in some, better quality, pool or spa water heat pumps and heaters.

Total Alkalinity (TA): a measurement of the ability of the water to resist changes in pH.  Water with a TA of 80-120 PPM is sufficiently buffered, so as to resist rapid changes in pH.  This makes pH management easier.  Additions of sodium bicarbonate are used to raise the total alkalinity:  1.5 pounds will raise the TA, of 10,000 gallons, by approximately 10 PPM.   High TA can be lowered by the addition of muriatic acid or dry acid (sodium bisulfate).

Total Dissolved Solids (TDS):   a measurement of the total PPM of all dissolved minerals and compounds.  High TDS can lead to water clarity problems, loss of sanitizer effectiveness and other issues.  Click here for some ordering information about TDS PockeTesters.

TriChlor: a highly concentrated stabilized chlorine.  Typically, it is approximately 90% Available Chlorine and is sold in a variety of tablet sizes and other shapes.  Acidic in  nature requiring periodic adjustment of the pH.  Recommended for pool use only.  A granular material is used to spot treat algae in masonry pools only.  The types of trichlor chlorine that are most commonly used in feeders and floaters are the tablets and other solid shapes.  No other product can be used in a chlorinator with an enclosed space.

Turbidity:  a technical term for describing the clarity of the water.  Cloudy water is turbid water.

UDVs:  Unit Dose Vials.  A new development in pool and spa water testing fro the LaMotte Company.  The precise amount is already sealed inside the UDV.  Just add the water sample and read the test result.  Speeds up the testing.  And because UDVs are disposable, there's no cleanup.

Ultraviolet (UV):  UV Sanitizing Systems can be, plumbed in-line, and used to reduce the overall population micro-organisms, as the water passes through the unit.  There is no residual effect of the UV, so backup sanitizing is highly recommended.  UV is also used in some Ozonators (refer to the listing for Ozone), in order to convert oxygen (O2) into ozone (O3).  Because UV rays from the Sun, can destroy chlorine or bromine, cyanuric acid conditioner/stabilizer is used to minimize the negative effect, of sunlight, on the chlorine concentration.

Underwater Lights:  specially designed for this purpose and meeting all of the appropriate codes.  Underwater lighting systems utilize low voltage transformers, sealed components and the design features for use in inground or aboveground pools.

Vacuuming:  the practice of drawing water into the filter, by using a "vacuum head" and hose attached to a pole.  Filter needs to be set on vacuum.  Follow manufacturer's instructions.  Vacuuming is used to remove debris and silt from the pool bottom.  Robotic Pool Cleaners vacuum the pool bottom and walls automatically, with a minimum of effort.

Venturi:  a means of creating a vacuum line in the return line of a pool or spa, that is used with ozonators, in order to inject ozone into the water stream.

Vinyl Liners:   used inside the formed shape of a pool and made of a heavy gauge of vinyl, pool liners are used to contain the water within the inner surfaces of the walls and bottom.   Vinyl liners are chemically inert and are available in a variety of colors and patterns.  Stock sizes are available, as well as custom sizes.  Vinyl liners help make the use of various materials as pool walls possible.  Vinyl hot tub liners are also used in some wooden hot tubs.

Water Chemistry:  in order to minimize the possibility of pool or spa water problems and to maximize the bathing pleasure, it is important to maintain or balance the common pool water parameters, within the suggested optimum ranges.  These parameters include:  sanitizer level, pH, total alkalinity, calcium hardness, chlorine stabilizer (outdoor chlorine pools only) and the control phosphates, nitrates and trace heavy metals.  Not all of these parameters are problematic:  a lot depends upon the nature and quality of the source water.

Water Mold:  a catch-all phrase that describes the problem of a bacterial or microorganism bloom that can cover broad areas and can cloud the water.  Can be pink or white in appearance.  Sometimes, present in a form that is describing as resembling "floating, shredded toilet tissue."  It is usually caused by the development of a resistant strain and is more common in pools or spas that have been maintained on biguanide, for long periods of time.

Water Quality:  refers to the state of the overall pool or spa water conditions, regarding such factors as:  sanitation, water chemistry, water clarity, water color  and the appearance of the underwater surfaces.  Water quality can become an issue in a variety of pool or spa problems, that detract from the goal of sparkling, crystal clear pool or spa water.

Wetting Agent::  something that helps make water wetter,  The opposite of "beading up."   Algaecides such as dimethyl benzyl ammonium chloride and close variants are useful in helping sanitizers, shock treatments and premium algaecides penetrate the outer layers of some type of resistant algae.  Refer to the listing for polymucosaccharide for additional information.

Winterizing:  pool closing.  A series of steps taken in order to protect the equipment and prepare the pool for the inactive winter period.

Zeolites:  a naturally-occurring mineral that is used as a replacement for ordinary sand filter media.  Produces higher clarity and quality water than would be possible with ordinary filter sand.  Lasts longer than filter sand.  One pound of zeolites can replace 2 pounds of filter sand.

Zinc:  used in some Ionizers and mineral sanitizers.  Zinc ions can function as a bactericide.