Perspiration, urine, saliva, suntan oil, cosmetics, lotions, dead skin and similar debris introduced to water by users and the environment.

The Oxidation Reduction Potential produced by strong oxidizing agents in a water solution. It is a measure of the oxidation level measured in millivolts by an ORP Meter.

A gaseous molecule composed of three (3) atoms of oxygen that is generated on site and used for oxidation of water contaminants.

A value expressing the relative acidity for basicity of a substance, such as water, as indicated by the hydrogen ion concentration. pH is expressed as a number on the scale of 0 to 14, 0 being most acidic. 1 to 7 being acidic, 7 being neutral, 7 to 14 being basic and 14 being most basic.

A dye that is used to measure pH.

A type of interior finish (a mixture of white cement and aggregate, which could be tinted or colored) which is applied to a concrete pool or spa. Also called Marcite or Marblite.

An abbreviation for parts per million. The unit of measurement used in chemical testing which indicates the parts by weight in relation to one million parts by weight of water. It is essentially identical to the term milligrams per liter (mg/L).

The coating of filter aid on the septum of a diatomaceous earth type filter at the beginning of each filter cycle.

The difference in pressure between two parts of a hydraulic system, such as the influent and effluent of a filter.

A mechanical device, usually powered by an electric motor, which causes hydraulic flow and p[pressure for the purpose of filtration, heating and circulation of pool and spa water. Typically, a centrifugal pump design is used for pools and spas.

The quantity of water flowing past a designated point within a specified time, such as the number of gallons flowing in one minute (gpm).

The aperture of fitting through which the water under positive pressure returns into a pool or spa.

As defined by ASTM F1346, Performance Specification for Safety Covers and labeling Requirements for All Covers for Swimming Pools, Spas and Hot Tubs, a barrier (intended to be completely removed before entry of users), for swimming pools, spas, hot tubs or wading pools, attendant appurtenance and/or anchoring mechanisms which will – when properly labeled, installed, used and maintained in accordance with the manufacturer’s published instructions – reduce the risk of drowning of children under five years of age by inhibiting their access to the contained body of water, and by providing for the removal of any substantially hazardous level of collected surface water. These covers may be power or manual.

The precipitate that forms on surfaces in contact with water when the calcium hardness, pH or total alkalinity levels are too high.

Synonymous with Chelating or Metal-complexation agent, a sequestering agent reacts with potential stain-producing metal ions (i.e., copper, iron, etc.) to reduce staining of pool/spa surfaces and associated colored water.