The length of time required for the mass, concentration, or activity of a chemical or physical agent to be reduced by one-half. Alkaline water containing dissolved salts that interfere with some industrial processes and prevent soap from lathering. Water may be considered hard if it has a hardness greater than the typical hardness of water from the region.
Water flowing in a pipe loses head, pressure or energy as a result of friction losses.
Also see friction losses. A large pipe to which a series of smaller pipes are connected. Also called a manifold health hazards Any condition, including any device or water treatment practice, that may create an adverse effect on a person's well-being heat sensor A device that opens and closes a switch in response to changes in the temperature. This device might be a metal contact, or a thermocouple which generates a minute electrical current proportional to the difference in heat, or a variable resistor whose value changes in response to changes in temperature. Also called a temperature sensor.