The ability of capacity of water to resist change in pH; also known as the buffering capacity of water. Measured with a test kit and expressed as ppm.

The sum of both the free available and combined chlorines.

A measure of the total amount of dissolved matter in water, e.g. calcium, magnesium, carbonates, bicarbonates, metallic compounds, etc.

The sum of all resistances in a completed operating system.

Also known as Trichloro-s-triazinetrione. Most common in compressed form (tablets or sticks) with 90 percent or more available chlorine, approximately 55.5 percent stabilizer by weight, and with an approximate pH of 2.9.

Also known as Trichloro-s-triazinetrione. A form of organic chlorine, most common in compressed form (tablets or sticks) with 90 percent or more available chlorine, approximately 55.5 percent stabilizer by weight, and with an approximate pH of 2.9. See also Organic chlorine and Sodium dichloro-isocanurate.

Cloudy condition of water due to the presence of extremely fine particulate materials in suspension that interfere with the passage of light.

The period of time (usually in hours) required to circulate a volume of water equal to the pool or spa capacity.