SAND FILTER:  A filter tank, usually fiberglass or ABS plastic, filled with sand and gravel. The pump diffuses water over the top of the sand bed, and forces it through the sand and into the laterals on the bottom.

SANITIZER:  A chemical agent used to remove unwanted contaminants.

SCALE:  Usually whitish in color, scale forms on pool surfaces and equipment when mineral salts are forced out of solution. A scaling condition is one in which calcium hardness, pH and/or alkalinity levels are out of balance.

SEQUESTERING AGENT:  A sequestering agent ties-up minerals tightly in solution, preventing their precipitation, which colors the water and/or stains the pool. Synonymous to chelators, these are commonly called stain & scale chemicals.

SKIMMER:  A surface skimmer is a plumbing fitting set at water level, containing a weir mechanism and a debris basket. The skimmer is part of the suction side circulation system.

SKIMMER BASKET:  Beneath the lid, the basket strains debris, as the first line of defense in filtering the water.

SKIMMER NET:  Attached to a telescopic pole, a leaf rake is a very useful tool in keeping the pool clean. Also called a skimmer net are the flat, "dip and flip" nets, which aren't so useful.

SHOCK:  As a noun it loosely describes the products used in shocking, such as hypochlorites, potassium permonysulfate or hydrogen peroxide. As a verb it describes the act of bringing the sanitizer level up so high that breakpoint chlorination is reached. When breakpoint is reached, a "shock" or perhaps a "lightning bolt" is a better analogy, is sent through the water, tearing apart molecules and slashing through cell walls. Ultimate purification, man.

SHOTCRETE:  A different type of application of the concrete and sand mix which is used to "shoot the shell". Gunite is pumped dry and mixed with water at the gun, whereas shotcrete is pumped wet.

SNOWBELT: The northern half of the United States where freezing temperatures are particularly common.

SODA ASH:  A base, used to counteract an acidic condition by raising pH.

SODIUM BICARBONATE (baking soda):  Another base, however its properties will increase alkalinity more than pH. Used to raise Total Alkalinity levels.

SODIUM BISULFATE:  An granular form of acid, used to counteract a scaling condition by lowering pH and/or alkalinity.

SODIUM HYPOCHLORITE:  Liquid chlorine used in pools, identical yet stronger than Clorox bleach.

SODIUM TETRABORATE:  New technology that renders algae incapable of processing carbon dioxide, which they need to live.

SODIUM DICHLOR:  A granular form of chlorine that is stabilized with cyanuric acid. Used for shocking and super-chlorination.

SOFT WATER:  Water that has low calcium and/or magnesium content. Soap lathers easily in soft water.

SOLAR SYSTEM:  Black mats of miniature plastic tubes through which water is pumped, absorbing the heat as it passes through. These mats are roof mounted with up & down plumbing connecting it.

SOURCE:  Refers to the origination of electrical power. The source for your filter pump (load) is probably a timer clock.

SPA:  A filtered, hot water vessel with hydrotherapy jets and air induction. Can be portable or installed permanently. Jacuzzi is a brand name. 

STRAINER BASKET:  The second line of defense is a basket at the pump. The holes in this are smaller than those in a skimmer basket, and prevent the pump impeller from clogging up.

STRATOSPHERE: The second layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler higher up and warmer farther down

SUCTION SIDE:  The plumbing prior to and carrying water to the pump. This side is under vacuum pressure.

SUNBELT: The southern half of the United States where freezing temperatures rarely occur, and high temperatures are particularly common.

SUPER-CHLORINATION:  Applying 7 - 10 times the normal amounts of chlorine to the pool as an added "boost" for contaminant removal. Some refer to super-chlorinating as being less than shocking, in that breakpoint thresholds are not reached, or the terms may be used synonymously.