Water Chemistry and Disinfection Glossary of Terms


The common name for sodium dichlor. A fast- dissolving chlorine compound containing chlorine and cyanuric acid (stabilizer or conditioner). It has a neutral pH and is quick-dissolving, so it can be used for regular chlorination or superchlorination.


To kill pathogenic disease-causing organisms.


Also called TDS or total dissolved solids – A measure of the total amount of dissolved matter in water. Examples are calcium, magnesium, carbonates, bicarbonates, sodium, chlorides and metals. High levels can cause corrosion, coloured water or salty taste. Maximum level is usually 2500 ppm for pools. Maximum level for spas is 1500 ppm over starting level.


An indicator reagent used for the determination of free and total chlorine, bromine, ozone and other oxidizers in water. Better than using OTO for chlorine because it measures free chlorine.


Chemically, sodium bisulphate. A dry white crystal that produces acid when added to water. It is used for lowering pH and total alkalinity. Safer to handle than muriatic acid.


The combination, agglomeration, aggregation or coagulation of suspended particles in such a way that they form small clumps or tufts (called floc).


The amount of free chlorine in the pool or spa water that is available to sanitize or disinfect the water. Sometimes called residual or available chlorine.