What is a cross connection?
The term Cross Connection is a Plumbing term used in the water and plumbing industry that describes the physical connection between safe drinking water (potable water) to a line which contains a contaminant or a pollutant. A common example is a garden hose submerged in a tub of detergent while washing a car.

What is the most common form of a cross connection?
Ironically, the ordinary garden hose is the most common offender as it can be easily connected to the potable water supply and used for a variety of potentially dangerous applications.

What is meant by "Degree of Hazard?"
The degree of hazard is a commonly used phrase referring to cross connection programs, and is simply a determination on whether the substance in the non-potable system is toxic (health hazard) or non-toxic (non-health hazard).

What factors can cause back-siphonage?
Back-siphonage can be created when there is a stoppage of the water supply due to nearby fire fighting, repairs or breaks in city main, etc. The effect is similar to the sipping of an ice cream soda by inhaling through a straw, which induces a flow in the opposite direction.

What factors can cause a backpressure-backflow condition?
Backpressure-backflow is created whenever the downstream pressure exceeds the supply pressure, which is possible in installations such as heating systems, elevated tanks, and pressure-producing systems. An example would be a hot water space-heating boiler operating under 15-20 lbs. pressure coincidental with a reduction of the city water supply below such pressure (or higher in most commercial boilers). As water tends to flow in the direction of lease resistance, a backpressure-backflow condition would be created and the contaminated boiler water would flow into the potable water supply.

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