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1. What is backflow?

Backflow is the flow of water or other liquids, mixtures, or substances into the distribution pipes of a potable water supply from any source other than the intended source. There are 2 types of backflow: backpressure backflow and back-siphonage.

2. What is backpressure backflow?

Backpressure backflow is a form of backflow due to pressure created by mechanical means or other means which causes water or other liquids or substances to flow or move in a direction opposite to that which is intended. Backpressure backflow is caused by a downstream pressure that is greater than the upstream or supply pressure in a public water system. Backpressure can result from an increase in downstream pressure, a reduction in the potable water supply pressure, or a combination of both.

Causes of increases in downstream pressure: Pumps (such as wells and booster pumps), elevated tanks, temperature increases in boilers, etc.

Causes of decreases in downstream pressure: Water line flushing, fire fighting, or breaks in water mains.

3. What is back-siphonage?

Back-siphonage is a form of backflow due to reduced or sub-atmospheric pressure within a water system. Back-siphonage is caused by a negative pressure (i.e., a vacuum or partial vacuum) in a public water system. The effect is similar to drinking water through a straw. Back-siphonage can occur when there is a stoppage of water supply due to a nearby fire fighting, a break in a water main, and more.

4. What is a backflow preventer?

A backflow preventer is a testable or non-testable cross connection control device which prevents potential pollutants and contaminants from flowing into the public water system.

5. Why does a soft drink dispensing machine require backflow protection?

Soft drink dispensers (post-mix carbonators) use carbonated water mixed under pressure with syrup and water to provide soft drinks beverages. Many, if not most water pipes are made of copper. When carbonated water comes into contact with copper, it chemically dissolves the copper from the pipe. This copper-carbonate solution has been proven to be a risk to the digestive system.