Learn about the different types of contaminants that might put your family at risk.

Flow of water in a pipe or line in a direction opposite to normal flow; often associated with back siphonage or the flow of possibly contaminated water into a potable water system. 
backflow preventer
A device or system installed in a water line to stop backflow from a nonpotable source. 
The process in which beds of filter or ion exchange media are subjected to flow opposite to the service flow direction; to loosen the bed and to flush suspended matter (collected during the service run) to waste. 
Unicellular microorganisms which typically reproduce by cell division.  Although usually classed as plants, bacteria contain no chlorophyll. 
A substance which releases hydroxyl ions when dissolved in water.  Bases react with acids to form a neutral salt and water. 
The filter media or ion exchange resin in a column or other tank or operational vessel. 
bed depth
The height of the filter media or ion exchanger in the vessel after preparation for service expressed in inches or centimeters. 
bed expansion
The increase in volume of a bed of the ion filter or exchanger media during backwashing due to lifting and separation of the bed material.  Usually expressed as the percent of increase of bed depth. 
bicarbonate alkalinity
The alkalinity (HCO3) of a water due to the presence of bicarbonate ions. 
An oxidizing agent formulated to break down colored matter; includes the widely used hypochlorites, as well as perborates and other special purpose materials. 
The appearance in the effluent from a water conditioner of the material to be removed by the conditioner, such as hardness in the effluent of a softener, or turbidity in the effluent of a mechanical filter.  An indication that regeneration, backwashing, or other treatment is necessary for further service. 
A chemical which causes a solution to resist changes in pH, or to shift the pH to a specific value. 
buffer action
The action of certain ions in solution in opposing a change in hydrogen-ion concentration. 
buffer solution
A solution containing two or more substances which, in combination, resist any marked change in pH following addition of moderate amounts of either strong acid or base. 
A connection or a valve system that allows untreated water to flow to a water system while a water treatment unit is being regenerated, backwashed, or serviced; also applied to a special water line installed to provide untreated water to a particular tap, such as a sill cock.