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Glossary of Terms

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 decreasers (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.

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.

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

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, mineral purifiers, ionizers and 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.

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 aerugenosa. Bacterial growth is the direct result of inadequate sanitation and is effected by such factors as bather load, pool or spa cleanliness, water temperature and filtration.

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.

Balanced Water: water that is within the accepted water analysis parameters for: pH, sanitizer, total alkalinity, calcium hardness, chlorine stabilizer (chlorine pools only) and minerals.

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.

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

Biguanide: 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. Chlorine, bromine or non-chlorine shock will destroy the biguanide polymer.

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..

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.

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.

Calcium Carbonate: crystalline deposits 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.

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.

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.

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.

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

Chlorine, Combined: that form of chlorine that has reacted with waste products. Chloramines are the major constituent.

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 Syringaldezine and reported as PPM.

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

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.

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.

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.

Copper: used as an active ingredient in some algaecides (chelated copper algaecides) and as a component in Ionization units. Copper sulfate should not be used as a swimming pool algaecide. Usually, copper is not found in most municipal water supplies.

Copper Oxidation Sanitizers: an alternative pool water sanitizer that utilizes a stream of copper ions and various forms of active oxygen.

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

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.

Cyanuric Acid: 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 problematic conditions.

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.

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..

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.

GFI: ground fault interrupter. An electrical safety receptacle required for wet or outdoor locations.

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.

Heavy Metals: a term used to describe the presence of metallic elements such as iron, copper, manganese, etc.

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.

Ions: the electrically charged state that an element assumes in true solution. In the ionic state, ions are chemically reactive.

Iron: a mineral, which can occur naturally in water and can be especially high in well water. Can lead to staining and discoloration of the 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.

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.

Manganese: a mineral that can occasionally occur in well water. Even low concentrations can cause brown-black staining and discoloration. 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.

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

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.

Non-Chlorine Shock: 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..

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.

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.

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. 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.

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.

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 products.

Pool, Inground: a type of pool that is built into the ground, usually level with the surface. This type of pool can be constructed of masonry materials, fiberglass, or various structural materials with 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. Another type operates on low-voltage electricity and requires no other hookups. 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.

Phosphate Eliminators: a group of products based on lanthanum compounds. Works by eliminating phosphates from the water, thereby, denying algae a source of a vital nutrient and helps cause it to starve. Used properly, it can reduce the overall sanitizer requirements and help make an algae bloom less likely.

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.

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. Precipitation of calcium can lead to cloudy water or scale formation.

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.

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

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.
Sanitizers: chemicals or methods used to kill bacteria, viruses, algae and mold

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 impair 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.

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.

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.

Skimmer: the water-level device, in the pool wall, that aids in the removal of floating debris.

Soda Ash: sodium carbonate. The chemical used to raise the pH of water. Neutralizes acid. Not the same chemical as sodium bicarbonate 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 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 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. 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 Cover: 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

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

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.

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.

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 from the pool bottom.

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 liners are also used in some wooden hot tubs..

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.