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Swimming Pool Glossary


SAND: The filter medium used by a sand filter. It usually refers to quartz or silica, but may also refer to zeolites.

SAND FILTER: A filter using sand, or sand and gravel as the filter medium.

SANITISE: To kill all microorganisms, including bacteria and algae, and to remove unwanted contaminants.

SCALE: The precipitate that forms on surfaces in contact with water when the calcium hardness, pH or total alkalinity levels are too high. Scale may appear as grey, white or dark streaks on the plaster, fiberglass or vinyl. It may also appear as a hard crust at the waterline.

SCUM: The foreign matter which floats to the surface of the water and forms a layer or a film. It can also refer to a residue deposited on the tiles or walls of the pool.

SEDIMENT: The solid material that precipitates out of the water and settles to the floor of the pool.

SEQUESTERING AGENT: Also called Chelating Agent. A chemical or compound that combines with dissolved metals or minerals in the water to prevent them from coming out of solution, thus colouring the water or causing stains.

SEQUESTRANT: A chemical which holds metals in solution and helps prevent scaling. See Sequestering Agent.

SHOCK TREAT: Adding large amounts of an oxidiser such as chlorine, hydrogen peroxide or potassium peroxymonosulfate to the water to destroy ammonia and nitrogen compounds, chloramines and other contaminants.

SHOTCRETE: Similar to Gunite, but premixed.

SKIMMER: A device installed in the wall of a pool that is connected to the suction line of the pump. The suction pulls in water and floating contaminants.

SKIMMER BASKET: A removable basket or strainer placed in the skimmer, which is designed to trap large solids from the water before they get to the pump or filter.

SKIMMER GUTTER: Also called a Gutter. An overflow channel at the edge of the pool through which floating debris, oil and other things flow and empty into the compensation tank. Pools with gutters generally do not have skimmers.

SKIMMER NET: A net attached to a frame which is then attached to a pole and is used to remove large floating pollutants such as leaves and insects from the water's surface.

SKIMMER WEIR: The small floating door on the side of the skimmer over which water flows on its way to the skimmer. The weir prevents debris from floating back into the pool when the pump is off.

SLURRY: Water containing a high concentration of suspended solids. D.E. is usually added to the filter as a slurry by mixing the D.E. in some water.

SODA ASH: Chemically, Sodium Carbonate. A base that is used to raise the pH of acidic (below pH 7.0) water.

SODIUM BICARBONATE: Also called Baking Soda or Bicarb. A base that is used to raise Total Alkalinity in pool water with only a slight effect on the pH. Sodium bicarbonate can only raise the pH of the water to 8.5, regardless of the amount used. Care should be taken, however, to avoid adding large quantities at one time.

SODIUM BISULFATE: Also called Dry Acid. A granular form of acid used to lower the pH or Total Alkalinity of pool water.

SODIUM BROMIDE: A salt of bromine which is used to raise the bromine levels in a pool before using bromine tablets.

SODIUM CARBONATE: Also called Soda Ash. A base that is used to raise the pH of acidic (below pH 7.0) water.

SODIUM DICHLOR: A granular, stabilised organic chlorine compound providing 56% or 62% available chlorine that has a pH of 6.9. Used for regular chlorination. Should be used with caution for superchlorination as it can cause the stabiliser level to rise too high, resulting in chlorine lock.

SODIUM HYPOCHLORITE: Liquid chlorine for use in pools. It usually provides 12% to 15% available chlorine and has a pH of 13. It is generally cheap, but difficult and dangerous to handle. It also loses its potency rapidly and is usually only used in large commercial pools.

SODIUM MONOPERSULFATE: Active ingredient and chemical name of a non-chlorine shock treatment or non-chlorine oxidiser. See Non-Chlorine Shock.

SODIUM PERSULFATE: Active ingredient and chemical name of a non-chlorine shock treatment or non-chlorine oxidiser. See Non-Chlorine Shock.

SODIUM SULFITE: A chemical that can be used to neutralise chlorine or dechlorinate pool water.

SODIUM THIOSULFATE: A chemical that can be used to neutralise chlorine or dechlorinate pool water.

SOFT WATER: Water that has a low calcium and/or magnesium content. Soft water can result in the etching of the pool's surfaces, and should be increased with calcium chloride.

SOLAR COVER: A floating pool cover that increases the water temperature by absorption and transmission of solar radiation. It also reduces evaporation and pollution from the environment.

SOLAR HEATING SYSTEM: A system that consists of panels through which the pool water passes to increase its temperature by using the sun's heat.

STABILISED CHLORINE: A family of organic chlorine compounds that contain stabiliser (cyanuric acid or iso-cyanuric acid) to protect the chlorine from the degrading UV rays in sunlight. Most common types are dichlor and trichlor. The granular form is dichlor and the tablet or stick form is trichlor.

STABILISER: Also called Cyanuric Acid or Conditioner. A granular chemical added to the pool water which provides a shield to chlorine for protection from UV radiation. Too much can result in chlorine lock.

STAIN: A discolouration or a coloured deposit on the walls or bottom of a swimming pool. Stains are usually the result of metals such as iron, copper or manganese in the water. The stains may be green, gray, brown or black. They may discolour the water without affecting the clarity. Sometimes a sequestering agent, chelating agent or commercial stain-remover may remove them. If that doesn't work, the easiest way to remove the stains is to drain and acid wash the pool.

STAIN INHIBITOR: Also called a Sequestering or Chelating Agent. A chemical that will combine with dissolved metals in the water to prevent the metals from coming out of solution and so avoiding dicolouration of the water or stains.

SUPERCHLORINATION: Adding 7 - 10 times the normal dose of chlorine to the water to destroy ammonia, nitrogen, chloramines and other contaminants.

SUSPENDED SOLIDS: Insoluble solid particles that either float on the surface or are in suspension in the water causing cloudiness. They may be removed by filtration, but if the particles are too small a flocculant or coagulant is necessary to enable the filter to trap them.

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TDS: See Total Dissolved Solids

TEST KIT: A manual or electrical device used to measure specific chemical residuals, levels or demands in pool water. Kits usually contain reagents, vials, titrants and colour comparators for the tests. The most common tests are: pH, free available chlorine, combined chlorine, total alkalinity, calcium hardness, cyanuric acid and metals.

TEST STRIPS: Small plastic strips with pads attached that have been impregnated with reagents to test pool water. The strips are dipped into the water and the resulting colours are compared to a colour scale to determine the values.

TIME CLOCK: Also called a Timer. An electrical device that automatically turns the pump or pool cleaner on or off at predetermined intervals or times.

TITRATION: A method of testing for total alkalinity, calcium hardness and acid/base demand by adding a titrant, drop by drop, until a color change is observed.

TOTAL ALKALINITY: The total amount of alkaline materials present in the water, usually measured as carbonate alkalinity. It indicates the water's resistance to change in pH. Low total alkalinity causes pH bounce. High total alkalinity causes the pH to constantly rise.

TOTAL CHLORINE: The total amount of chlorine in the water. It is the sum of free available chlorine and combined chlorine.

TOTAL DISSOLVED SOLIDS: Also called TDS. A measure of everything that has ever dissolved in the water and all the matter that is in solution. The only way to lower TDS is to drain part of the water and replace it.

TRICHLOR: A slow-dissolving, tablet or granular stabilised organic chlorine compound which provides 90% available chlorine and has a pH of 2.9. It must be dispensed using a floating feeder or an in-line chlorinator. Trichlor contains cyanuric acid that prevents the chlorine from being destroyed by the ultraviolet rays of the sun. When using trichlor, the cyanuric acid level needs to be checked regularly to avoid chlorine lock.

TURBIDITY: The cloudy condition of the water due to the presence of extremely fine particles in suspension that are able to pass through the filter. Adding a flocculant or coagulant will clump the particles together so they can be trapped in the filter.

TURNOVER: Also called Turnover Rate. The period of time, in hours, required by the pump to circulate the volume of water in the pool. Pool capacity in kilolitres divided by pump flow rate in kilolitres per hour (m3/h) will give the turnover rate in hours.

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