Acids   
Chemicals which lower pH and alkalinity and remove stain and scale, such as hydrochloric (muriatic) acid and sodium bisulfate. 

Acid Demand   
A measure of the amount of acid required to reduce the pH of a volume of water to a predetermined level - accomplished by titration with a standard acid (Acid Demand Test).

Algae   
Microscopic aquatic plant life which can grow on surfaces or float freely in water.  Though harmless to swimmers, presence of algae discolors the water and indicates improper sanitation. 

Algaecide   
A chemical used to kill or prevent the growth of algae.

Alkalinity   
See Total Alkalinity.

Bacteria   
Very small organisms continuously entering the water with swimmers, rain, dust, etc.  Without proper sanitation, pools and spas are a good breeding-ground for bacteria. 

Balanced Water
Water which is neither corrosive nor scaling because its pH, total alkalinity, calcium harness and temperature correct relative to one another. 

Bases   
Chemicals which raise pH, such as sodium carbonate (soda ash) or caustic soda (lye).

Base Demand   
A measure of the amount of base required to raise the pH of a volume of water to a predetermined level - accomplished by titration with a standard base (Base Demand Test).

Bather Load   
The number of individuals using a pool or spa in 24 hours.  A pool or spas principal source of bacterial and organic contamination.

Break-Point Chlorination   
The process of adding free chlorine to pool water sufficient to oxidize chloramines and organic matter. 

Bromine   
Chemical sanitizer, biocide, strong oxidizer.  

Buffer   
A chemical which neutralizes either acids or bases thus stabilizing pH, e.g. sodium bicarbonate

Calcium Hardness   
The concentration calcium and magnesium ions dissolved in a water expressed as ppm calcium carbonate.

Caustic Soda   
Sodium hydroxide or lye; strong base; raises pH.

Chloramines   
Combined Chlorine; chlorine-ammonia compounds; not effective as sanitizers; responsible for eye, skin irritation, strong chlorine odors.

Chlorine    
Chemical sanitizer, biocide, strong oxidizer.

Chlorine, Combined   
The reaction products of chlorine and ammonia (chloramines) and chlorine and organic matter.

Chlorine Demand    
Quantity of chlorine required by a water before a free chlorine residual is obtained.

Chlorine, Free   
HOCl concentration; sanitizing form of chlorine.

Conditioner   
See Cyanuric Acid

Corrosion   
The dissolving of copper, steel, concrete.  

Cyanuric Acid   
An ultraviolet (UV) stabilizer for chlorine.

Disinfect   
The act of killing microorganisms. 

Dry Acid   
A granular chemical used to lower pH and/or total alkalinity - usually sodium bisulfate.

Langelier Index   
A reference arrived at after considering a water’s calcium hardness, total alkalinity, pH, temperature; useful in determining if a water is scale-forming, corrosive or neither. 

Muriatic Acid    
Hydrochloric acid 

Non-Chlorine Shock   
A fast-acting, oxygen-based oxidizer of chloramines and organic matter - usually sodium persulfate.

Organic Wastes   
Wastes such as saliva, urine, feces, perspiration and sun-tan lotions - most are not filterable, so must be removed by oxidation.

OTO  
A reagent used in chlorine, bromine tests. 

Oxidizing    
The process of “wet burning” organics into simpler forms - ultimately carbon dioxide and water.

pH   
A measure of the hydrogen ion concentration or acid/base nature of a water.  The pH scale runs from 0 - 7 - 14.  The mid-point (7) is neutral; less than 7, acid (acidic); greater than 7, base (basic or alkaline).

pH of Saturation   
The pH for perfect water balance - considering a water’s calcium hardness, total alkalinity and temperature.  

Phenol Red    
A color indicator used for testing pH from 6.8 - 8.4.

ppm   
The abbreviation for the weight ratio parts per million.

Saturation Index   
See Langelier's Index.

Scale   
Any hard, insoluble, mineral deposit which forms on pool and spa surfaces and clog filters, heaters and pumps (usually calcium carbonate). 

Shock   
The act of ridding a pool of organic waste via oxidization. 

Soda Ash   
See sodium carbonate.

Sodium Bicarbonate   
(bi-carb, baking soda)  A chemical used to increase the alkalinity and stabilize (buffer) the pH of water. 

Sodium Bisulfate    
(dry acid)  A chemical used to lower the pH and total alkalinity of water. 

Stabilizer   
See Cyanuric Acid.

Superchlorination   
The application of free chlorine to destroy undesirable organics and chloramines.

Titration   
The method of adding a measured volume of reagent of known strength to a water sample of known volume until a specific color change (endpoint) indicates the completion of the reaction.

Total Alkalinity   
A measure of the acid-neutralizing capacity of a water - expressed as hydroxide, carbonate and bicarbonate types. 

Total Dissolved Solids (TDS)   
The electrical conductivity of a water, expressed in ppm, as if that conductivity were caused by a dissolved salt (usually sodium chloride or calcium carbonate).