Water Quality and Maintenance Glossary of Terms


Refers to volatile, combustible and sometimes biodegradable chemical compounds containing carbon atoms bonded together with other elements. The principal groups of organic substances found in water are proteins, carbohydrates, fats and oils. See organic waste.


An organism that causes disease.


A substance separating, in solid particles, from a liquid as a result of a chemical or physical change. It also means to form a precipitate.


The chemical agents, dyes, indicators or titrants used in testing various aspects of water quality.


This usually refers to the filter medium used by a sand filter. The grade most often specified by filter manufacturers is grade No. 20 with a particle size of 45 to 55 mm (millimeters).


To render sanitary: to kill all living things, including bacteria and algae. Similar to sterilize.


The precipitate that forms on surfaces in contact with water when the calcium hardness, pH or total alkalinity levels are too high. Results from chemically unbalanced pool and spa water. Scale may appear as grey, white or dark streaks on the plaster, fiberglass or vinyl. It may also appear as a hard crust around the tile.


The extraneous or foreign matter which rises to the surface of the water and forms a layer or a film there. It can also be a residue deposited on the tile or walls of the pool or spa. Sources of scum are soap, oil, deodorant, hair spray, suntan lotions and others.


The solid material settled out from the water.