Pool Chemical Glossary - Direct Pool Supplies

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ACID DEMAND:  A test result which indicates how much acid (pH decreaser) if any, should be added to the water to provide a balanced proportion of acid to alkaline materials.

ALGAE: Tiny plants which grow in the water and can discolour it. Particularly active in warm water. Algae may be green, brown or black.

ALGAECIDES: Chemicals which kill algae and prevent new algae growth.

ALKALINITY: A combination of natural minerals in the water. The opposite of acidity on a measurement of pH.

BACTERIA: Microscopic organisms (germs) which can cause illness.

CHELATING AGENTS: Chemicals that combine with dissolved metals to prevent water discoloration.

CHLORAMINES: The combined form of chlorine after oxidation of impurities. Cause eye irritation and four chlorine-like odours. This form of chlorine is not an effective disinfectant.

CHLORINE: The most commonly used disinfecting agent for swimming pools because it is the best chemical material available.

CHLORINE DEMAND: The materials in the water which use up chlorine, such as bacteria, algae, dirt, leaves, grass clippings and swimmers wastes. The chlorine demand must be satisfied before a chlorine residual is available to disinfect the pool water.

CHLORINE RESIDUAL: The chlorine level in the water after the chlorine demand has been satisfied. The free chlorine residual is the true measure of potential chlorine disinfection.

COMBINED CHLORINE: Weak chlorine which is combined with the contaminants in the water.

CYANURIC ACID: (See stabilizer. Also called conditioner)

DPD1: An indicator solution used to measure the free chlorine residual.

DPD3: An indicator solution used to measure the total chlorine

DRY ACID: (Sodium bisulfate) A granular material which is used to lower the pH or total alkalinity.

FREE CHLORINE: Hypochlorous acid or hypochlorite. This is the active chlorine that kills bacteria and algae and keeps your pool clear and clean.

HARDNESS: The amount of calcium or magnesium dissolved in the water. High levels contribute to scale deposits.

HYPOCHLOROUS ACID: The active form of chlorine in water. The material which performs the sanitizing and oxidizing. (free chlorine)

MURIATIC ACID: A liquid used for lowering pH or total alkalinity.

OTO: orthotolidine. And outdated indicator solution that was used to measure the total chlorine residual.

pH: A system for measuring the acidity/alkalinity of water. Readings above 7 are alkaline; readings below 7 are acidic.

PPM: Parts per million, the standard measure of concentration in swimming pools. An example is one cent in $10,000.

PHENOL RED: The indicator solution which measures pH.

SHOCK TREATMENT: (See super-chlorination)

SODA ASH: An additive which is used to raise the pH of the water. Also know as sodium carbonate.

SODIUM BICARBONATE:  An additive which is used to increase the total alkalinity or pH or the water.

STABILIZER: (Cyanuric acid or conditioner) s-triazinetrione, also called Isocyanuric Acid. A chemical which helps prolong the useful life of chlorine in the water by slowing down chlorine decay due to sunlight.

SUPERCHLORINATION: (Shock treatment) The practice of adding 5-10 times the normal daily chlorine dose to destroy algae, or to prevent problems after heavy bather loads or severe rains.

TOTAL ALKALINITY: This helps the water resist changes in pH.

TOTAL CHLORINE: The sum of the amount of free chlorine and combined chlorine.

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