Chemicals used to lower the pH and/or total alkalinity, including: liquid muriatic acid (hydrochloric acid) or granular pH decreaser (sodium bisulfate).

Amount of acid required to lower pH to between 7.2 - 7.6.

Single-celled plant, most common in pools are: blue-green, yellow mustard or black.

Chemicals that kill algae, including: quaternary ammonium compounds, copper, silver or polymer (poly quat), chlorine and bromine.

Inhibits or retards algae growth, but does not necessarily kill the algae.

A.k.a. basic. Opposite of acidic; pH levels above 7.0 (neutral).

A.k.a. aluminum sulfate; used to clarify water through flocculation.

Negatively charged ion.

Reversing of the flow of water through the filter and sending it to waste.

Single-celled, microorganisms varying from harmless to pathogenic.

Chemicals that kill bacteria, including: chlorine, bromine, biguanide, ozone and silver.

Water within ideal parameters for: pH, sanitizer, total alkalinity, calcium hardness, chlorine stabilizer (chlorine pools only) and minerals.

A.k.a. alkaline. Opposite of acidic; pH levels above 7.0 (neutral).

Slippery coating of microorganisms that can develop in poorly sanitized pools and spas.

The natural breakdown or decomposition by which organic substances are degraded into harmless basic materials, including: water, carbon dioxide, nitrogen, etc.

Amount of chlorine required to completely oxidize all organics and decompose all combined chlorine present in pool / spa water.

Throwing or dispersing dry granular chemicals across the surface of a swimming pool.

Sodium bicarbonate (baking soda); used to stabilize pH in pool / spa water.

A.k.a. scales; crystalline deposits that can form on all under water surfaces when water is excessively high in calcium hardness.

Used to raise the calcium hardness of the water.

Measurement of the dissolved calcium content of the water.

Filter that removes particles from pool / spa water through a porous, pleated insert or bag.

Positively charged ion.

Chemical compounds that react with minerals (heavy metals) such as iron, copper, manganese and calcium and forms stable, soluble products; used to prevent staining and discoloration and is the preferred method for treating iron, copper and manganese.

Forms of combined chlorine formed by the reaction of chlorine with nitrogen containing waste products.

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.

Naturally occurring metal; used as an active ingredient in some algaecides and as a component in ionizers / mineral purifiers.

Protects chlorine from being destroyed by UV-rays from the sun; makes chlorine last longer.

Degradation of surfaces proximate to pool / spa water resulting from low pH.

A.k.a. blue-green algae; found in swimming pools.

Active ingredient in chlorine conditioners / stabilizers.

Naturally occurring sedimentary rock, crushed and used as filter media in D.E. filters for pools / spas.

A.k.a. sodium bisulfate; used to lower the pH and total alkalinity.

Organic agents that speed the natural breakdown or decomposition of oily wastes and organic residues in pools and spas.

Materials used to remove dirt and debris from pool / spa water, including: diatomaceous earth, sand and zeolites.

When insoluble fine particles precipitate from suspension.

Pockets of gas trapped in pool or spa water resulting from agitation, surfactants or body oils.Gallon (US)U.S. unit of liquid volume; 1 gallon (US) = 3.8 liters.

Family of elements including chlorine and bromine.

Describes water that is high in calcium or magnesium.

Describes the presence of metallic elements such as iron, copper, manganese, etc.

Wooden alternative to the typical spa.

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

A.k.a. H2O2; used as a shock treatment for pools and spas

Equipment designed to sanitize pool / spa water as water passes over electrodes charged with a low level of copper and silver ions.

Naturally occurring mineral in well water and other water sources.

Metric unit of weight; 1 kilogram = 2.2 pounds.

Rare earth element.

Describes the movement of slowly soluble constituents into pool water; can affect pH, total alkalinity and calcium hardness.

Metric unit of volume; 1 U.S. Gallon = 3.8 liters.

Naturally occurring mineral that is common in hard water.

Mineral that can occasionally occur in well water; causes brown-black staining and discoloration problems.

Filter that removes very fine particles, including: dead algae and bacteria.

Device that releases copper, silver or zinc ions into the water at very low levels; used for sanitization.

Naturally occurring components of water, including: salt, calcium, magnesium, iron, manganese, copper, etc.

Living organisms, including: algae, bacteria, mold and fungus.

Dark blotches, spots or stains that can appear on some pool surfaces.

A.k.a. hydrochloric acid; used to lower pH, lower total alkalinity, acid washing and stain removal.

Vital nutrient for algae that stimulates algal growth and leads to higher consumption of chlorine.

A.k.a. potassium monopersulfate, monopersulfate compound and potassium peroxymonosulfate; used as a shock treatment.

Steps taken to restore the pool to operational status after a closure.ORP (Oxidation Reduction Potential)Measurement of the oxidizing power of pool water containing chlorine or bromine.

Chemical reaction where organic matter is destroyed by the action of chlorine, bromine, ozone, hydrogen peroxide or non-chlorine shock.

Device for producing Ozone (O3).Ozone (O3)Powerful oxidizing agent typically produced by an Ozonator installed in a pool or spa; used to destroy organic waste and byproducts and help in the control of algae and bacteria.

Limits, ranges or boundary-determining characteristics.

Describes infectious, disease-causing microorganisms in pools such as e. coli or pseudomonas aeruginosa.

The pH scale goes from 0 (acidic) to 14 (alkaline); 7 is neutral. The ideal range for most pools and spas is 7.2-7.8.

Salt or ester of phosphoric acid; in excess it stimulates algae growth in pools. Collect in pool water from decomposition of vegetation, urine, body wastes, and some mineral or scale treatments.

A.k.a. Non-Chlorine Shock.

Parts per million; used as a unit or measurement of concentration. 1 PPM equals 1 pound per 1 million pounds of water.

Formation of an insoluble chemical compound which drops out of solution.

A.k.a. quats; used to treat the most common varieties of algae.

Technical term for a testing solution.

Equipment that converts salt into chlorine in line as the water passes over specially-coated titanium electrodes.

Tank-shaped filter that utilizes a special grade of sand, as a filter media.

Chemicals or equipment used to kill bacteria, viruses, algae and mold; includes: chlorine, bromine, biguanide, ozone, ionization, mineral purifiers, salt chlorine generators, ultraviolet (UV) sanitizing, etc.

A.k.a. calcium carbonate precipitate.

Whitish coating on underwater surfaces. In excess causes problems with filtration and pool heating. Scale occurs if the calcium hardness exceeds 400 PPM and the pool chemistry is not properly maintained.

Used to treat calcium problems in pool water.

A.k.a superchlorination; used to break down combined chlorine, organic waste and contamination and re-establish a positive level of Free Chlorine.

ultra fine particles that settle to the bottom of a pool during periods of inactivity.

Used in ionization units; silver ions can function as a bactericide.

Intake filter on the side of a pool that aids in the removal of floating debris and regulates the water-level.

A.k.a. biofilm; algal or bacterial film often due to inadequate sanitation or water circulation.

A.k.a. sodium carbonate; used to raise the pH of water and neutralize acid.

A.k.a. sodium acid carbonate, sodium hydrogen carbonate, baking soda; used to raise the total alkalinity of water and create a pH buffer.

Used to treat a variety of resistant conditions, including: "pink" algae, water mold, slimes and yellow-mustard algae.

A.k.a. soda ash; used to raise the pH of water and neutralize acid.

Acidic, granular chemical used to lower the pH and/or total alkalinity.

Form of stabilized chlorine.

Caustic, high pH by-product produced by common types of salt chlorine generators. Also known as lye or caustic soda.

Liquid chlorine solution.

Water that is low in calcium and magnesium hardness. Soft water is corrosive to masonry surfaces and underwater metal parts.

Buoyant, air bubble filled plastic sheet placed directly on water surface. Warms water by capturing any solar rays and by reducing evaporation.

Type of heater powered by solar energy which can be plumbed to the pool for decreased power consumption.

Small recreational basin; typically features heated water and air jets.

A linear, shallow open area of ground which contours direct water flow.

A.k.a. Shocking pool water.Total Alkalinity (TA)The ability of water to resist changes in pH. Ideal is 80-120 PPM.

Measurement of the total amount of FREE CHLORINE plus the amount of COMBINED CHLORINE; reported in PPM.

(TDS)Measurement in PPM of all dissolved compounds in the water including metals, minerals and salts.

Degree to which light is blocked because pool / spa water is cloudy.Ultraviolet (UV)Used in line to reduce the overall population of micro-organisms in water.

Drawing unwanted debris and water from the bottom of a pool into the filter by using a hose attached to a vacuum head, typically attached to a pole.

A vacuum line in the return line of a pool or spa; used with ozonators, in order to inject ozone into water.

Proper balance of common pool water parameters, including: sanitizer level, pH, total alkalinity, calcium hardness, chlorine levels, phosphate control, nitrate levels, heavy metals, etc.Water

General term that describes a bacterial or microorganism bloom that can cover broad areas and can cloud the water. Can be pink or white in appearance.

The state of the overall pool or spa water conditions, specifically including: water clarity, water color, overall water chemistry, sanitation and the appearance of underwater surfaces.

Component that helps make water wetter by minimizing surface tension of the water molecule.

A.k.a. closing. Steps taken to protect equipment and prepare the pool for an inactive period.

Naturally-occurring mineral used as a replacement for ordinary sand filter media. Lasts longer and produces higher clarity and quality water than ordinary filter sand. 1 lb zeolite can replace 2 lbs filter sand.

Metallic chemical element; used in some ionization units. Zinc ions can function as a bactericide.