Acid Chemical compound characterized by sour taste and a pH less than 7 with the ability, when in solution, to react with a base to form a salt and to turn litmus red. Also, a substance that releases hydrogen ions (H+) in water. In pool water maintenance muriatic acid and sodium bisulfate, also an acid, are used to lower pH and alkalinity. Acid Demand A measure of the amount of acid required to reduce pH to a predetermined level. This can be accomplished using an acid titration procedure, referred to as an Acid Demand Test. Algae Tiny, hardy, plantlike organisms that will rapidly proliferate in water absent adequate sanitizer. Algae do not cause diseases but can harbor bacteria that do. Green-, black-, and mustard-colored algae are commonly seen in problem pools and spas. Here, besides being aesthetically displeasing, algae are a safety concern because they create slippery surfaces and can make it impossible to see a swimmer in trouble. Algaecide A chemical used to kill algae. Algaestat A chemical used to inhibit the growth of algae. Alkalinity See TOTAL ALKALINITY. Analyte Parameter that is the subject of the water analysis, such as pH or free chlorine. Bacteria Potentially disease-causing, one-celled organisms requiring control by sanitizing agents. Balanced Water Water that is chemically stable, that is, neither corrosive nor scaling forming. The Langelier Saturation Index (LSI) for perfectly balanced water equals zero. Base Chemical compounds characterized by bitter taste and a pH greater than 7 with the ability, when in solution, to react with an acid to form a salt; also referred to as alkalis. Also, a substance that releases hydroxyl ions (OH-) in water. In pool water maintenance two bases are commonly used: soda ash (sodium carbonate), to increase pH, and baking soda, to increase total alkalinity. Base Demand A measure of the amount of alkali material required to raise pH to a predetermined level. This can be accomplished by use of a base titration procedure, referred to as a Base Demand Test. Breakpoint Chlorination Dosing water with sufficient free chlorine to remove combined chorine (chloramines). Dosage is calculated as 10 times the combined chlorine value. Bromamines Byproducts formed when bromine reacts with contaminants in pool and spa water; unlike chloramines (combined chlorine), bromamines are effective sanitizers and do not need to be eliminated. Bromine A compound containing the halogen bromine which is used to kill microorganisms in water. Buffer Solution An aqueous mixture that resists pH change when an acid or base is added. Burette Labware consisting of a long, graduated glass tube with a tap at one end held with a clamp so that the tap is lowermost. It\'s used as a reservoir for a chemical during titration. Calcium Hardness A measure of the calcium salts dissolved in water. Calcium hardness is the main component of scale. Chloramines See COMBINED CHLORINE. Chlorine A compound containing the halogen chlorine which is used to kill microorganisms in water. Chlorine Demand Amount of chlorine required to eliminate all contaminants in the water. Chlorine Residual The amount of chlorine still available for sanitation and oxidation after the chlorine demand has been satisfied. Colorimetric Test Test method where reagents react with the analyte of interest to produce a color proportional to the concentration of the analyte. Combined Chlorine Smelly, irritating reaction product of free chlorine with ammonia and other nitrogen-based contaminants in water; also known as chloramines. Conditioner Another term for cyanuric acid, which is used to slow down the degradation of chlorine by the UV component of sunlight. See STABILIZER. Corrosion An eating away of a material caused by chemical reactions. Water low in calcium hardness can be corrosive; it will dissolve metals, etch plaster, and pit concrete. Cyanuric Acid Chemical used to prevent the degradation of chlorine by ultraviolet (UV) light. Disinfect To kill all disease-causing organisms. DPD Common abbreviation for N,N-diethyl-p-phenylenediamine, a reagent used to determine both total chlorine and free chlorine levels. Will also detect total bromine level. Preferable method for testing pool and spa water; usually mandated for use at public facilities by health authorities. Turns the sample water pink. Dropper Bottle Reagent container used in drop-count titrations; the size of the hole must be tightly controlled to ensure the proper amount of reagent is dispensed with each drop. Free Chlorine Chlorine available to sanitize and oxidize water; also known as free available chlorine. Total Chlorine The sum of free chlorine and combined chlorine. Halogen An element found in Group VII of the Periodic Table, including chlorine, bromine, and iodine, characterized by the ability to disinfect water. Hardness (Hard Water) A property of water that contains ions which form scale. “Total hardness” is considered to be the sum of calcium and magnesium hardness. In water treatment, calcium and magnesium hardness values are usually expressed as calcium carbonate to facilitate treatment calculations. Hardness can be removed by ion exchange softening. Langelier Saturation (a/k/a Stability) Index (LSI) A number derived from a formula that considers the interrelationships between calcium hardness, total alkalinity, and pH at a given temperature, used to determine the scaling or corrosive tendency of a water. An LSI of zero indicates water at equilibrium. To avoid number crunching, this value can be determined with the aid of Taylor\'s Watergram. Long Viewpath Comparator A variation of the Taylor Slide comparator that employs a longer test cell to increase test sensitivity. See SLIDE COMPARATOR. Click to read more. Magnesium Hardness A measure of the magnesium salts dissolved in water; not used in calculating the Langelier Saturation Index. Midget™ Comparator A handheld device manufactured by Taylor for colorimetric testing that employs eight liquid-color standards. Not appropriate for use with colored and/or turbid water samples. Click to read more. Muriatic Acid Also known as hydrochloric acid; used to reduce pH and alkalinity. May be used to remove stain and scale. Oxidizer A compound (e.g., chlorine, bromine, potassium monopersulfate) used to “burn up” organic contaminants in water. See SHOCKING. OT (OTO) Common abbreviation for orthotolidine, a reagent used to determine total chlorine. OT cannot distinguish between free available chlorine and combined chlorine. Also detects total bromine. Turns the sample water yellow. pH A measure of the acidity /basicity of an aqueous solution. The pH scale runs from 0 to 14 with 7 being the neutral midpoint. A pH of less than 7 is on the acid side of the scale; a pH greater than 7 is on the basic (alkaline) side of the scale. pH of Saturation The ideal pH for perfect water balance in relation to a particular total alkalinity level and a particular calcium hardness level, at a particular temperature. The pH where the Langelier Saturation (a/k/a Stability) Index equals zero. Phenol Red Chemical reagent used for testing pH in the range of 6.8-8.4. ppm Abbreviation for parts per million. Sanitize To kill all living organisms, including algae, harmful bacteria, and other pathogens. Scale A buildup of crusty mineral deposits principally composed of calcium carbonate. Scaling water in piping will gradually reduce circulation, and will inhibit heat transfer. Shocking The periodic addition of an oxidizing chemical to rid pool and spa water of organic contaminants such as body oils, perspiration, personal care products, dust and dirt, etc. A non-chlorine shocking agent, such as potassium monopersulfate, cannot leave a sanitizing residual whereas the various chlorine compounds used for this purpose, such as calcium hypochlorite, can; however, use of a non-chlorine shock will allow swimmers to reenter the water sooner. See SUPERCHLORINATION. Slide™ Comparator A handheld device manufactured by Taylor for colorimetric testing that employs nine liquid-color standards. Used to compensate for color and/or turbidity in the water sample. Click to read more. Soft Water Water lacking the ions which form scale. May be achieved by ion exchange softening. See HARDNESS. Soda Ash Also known as sodium carbonate, used to raise pH levels. Sodium Bisulfate Chemical used to lower pH and total alkalinity; also known as dry acid. Stabilizer Another term for cyanuric acid, which is used to slow down the degradation of chlorine by the UV component of sunlight. See CONDITIONER. Superchlorination Application of a large dosage of chlorine all at once to destroy built-up chloramines and scour the pool of oxidizable organic contaminants, including a green algae bloom. Typically the chlorine level would be raised to 30 ppm and then allowed to fall back gradually to below 5-10 ppm before swimming resumes. See SHOCKING. Titration A method of testing by adding a reagent of known strength to a water sample until a specific color change indicates the endpoint of the reaction. Total Alkalinity A measure of the acid-neutralizing capacity of water which indicates its buffering ability, i.e., resistance to changes in pH. Generally, the higher the total alkalinity, the greater the resistance to pH change. Total Dissolved Solids (TDS) The measure of all solids dissolved in a sample of water. Water Quality A measure of water\'s suitability for a specific application. The intended use determines what characteristics are desirable in the water chemistry. Water Test Kit Apparatus for determining water quality. See WATER QUALITY. Water Treatment Program A plan for managing water quality by mechanical and/or chemical means. Watergram™ A type of slide rule used to make calculating the Langelier Saturation (a/k/a Stability) Index easy; available only from Taylor.