BACKFLOW PREVENTION:
A term used to include all parts of the Plumbing Trade that deal with protection of the Potable Water System, (The Drinking Water System) and includes Cross Connection Control, Backflow Preventers, Installations, Testing, maintenance, Regulations, Bylaws, Surveys and enforcement.

BACKFLOW:
In plumbing, the term means the reversal of the normal direction of flow in a piping System. Plumbing systems are designed for the internal liquids to flow in a desired direction,either into and around a building, (Domestic Potable Water) or out of a building (Sewage, Wastes or Storm products) and will flow either by force or by gravity. In the Domestic Potable Water System, water is usually under pressure (force) and will flow in the direction from high pressure to low pressure.Under certain physical conditions, water may be forced, persuaded or pulled in the undesireable direction causing Backflow. These conditions are known as Back Siphonage and/or Back Pressure.

BACK SIPHONAGE:
A condition caused by the loss or reduction of the supply pressure ( to atmospheric or below atmospheric pressure) pulling in the wrong direction. This may happen when the city street main breaks or the internal piping system is shut off and cut for service or repairs.

BACK PRESSURE:
A condition caused when the system end pressure raises higher than the supply pressure. This can happen by thermal expansion thru a boiler or mechanical means by a pump or high pressure piping systems.