A mechanical device for applying chemicals to pool or spa water.

A compound formed when chlorine combines with nitrogen and ammonia, which causes eye and skin irritation and has a strong, objectionable odor.

A device used to apply or to deliver a chlorine disinfectant to water at a controlled rate.

Equipment that generates chlorine, hypochlorous acid, or hypochlorite on-site for disinfection and oxidation of water contaminants. Most commonly a salt conversion / chlorine generator which converts sodium chloride (salt) to sodium hypochlorite (bleach) which disinfects the water.

An arrangement of mechanical equipment or components, connected by piping to a pool or spa in a closed circuit. The function of a circulation system is to direct water from the pool or spa, causing it to flow through the various system components for purposes of clarifying, heating, purifying and returning the water back to the original body of water.

A chemical that coagulates and neutralizes suspended particles in water. There are two types: inorganic salts of aluminum or iron, and water-soluble organic polyelectrolyte polymers.

The portion of the total chlorine existing in water in chemical combination with ammonia, nitrogen, and/or organic compounds; mostly comprised of chloramines.

The cap on the pool or spa wall that provides a finishing edge around the pool or spa. Can be formed, cast in place or pre-cast, or pre-fabricated from metal or plastic materials. It may be used as part of the system that secures a vinyl liner to the top of the pool wall.

Also called Stabilizer, Isocyanuric acid, Conditioner or Triazinetrione, a chemical that helps reduce the excess loss of chlorine in water due to the ultraviolet rays of the sun.

A filter that utilizes a thin coating a diatomaceous earth (DE) over a porous fabric as it filter medium that periodically must be replaced.

The filtering medium of a diatomaceous earth filter composed of microscopic fossil skeletons of the “diatom,” a tiny freshwater marine plankton.

Energy or chemicals to kill undesirable or pathogenic (disease causing ) organisms, and having a measurable residual at a level adequate to make the desired kill.

A reagent and test method that specifically measures bromine and free available and total chlorine; produces a series of colors from pale pink to dark red.

The water that flows out of a filter, pump or other device.

A basis for indicating the resistance in a hydraulic system, equivalent to the height of a column of water that would cause the same resistance (100 feet of head equals 13 pounds per square inch).