Questions about Backflow and Cross connection devices
What is a cross-connection?
A cross-connection is a temporary or permanent link between a potable (drinking) water system and any source containing non-potable water or other substances from which backflow may occur.
Examples include the piping between a public water system, or a citizen's water system and a heating or cooling system, fire system or irrigation system.
What is a cross-connection control device?
A cross-connection control device is a mechanical device that prohibits backflow of water into the public drinking water. The main testable types of cross-connection control devices are the reduced-pressure principle assembly, the pressure vacuum breaker assembly, the double-check valve assembly and registered Air Gaps. Examples of secondary types of devices are the hose connection vacuum breakers, atmospheric vacuum breakers and residential dual check valves. Source: City of Calgary's website.
What is backflow?
Backflow is the undesirable reversal of non-potable (untreated) water (or other substances) through an unprotected cross-connection and into the piping of a public water system or a citizen's drinking water system.
There are two causes of backflow:
Backsiphonage: The reversal of normal flow in a system caused by a vacuum in the supply piping. This can also happen if there is an interruption of the water supply due to nearby fire-fighting, repairs or breaks in the water supply mains.
Backpressure: The reversal of normal flow in a system due to pressure higher than the supply pressure. This happens when there is an increase in downstream pressure caused by pumps, temperature increases in boilers, elevated tanks or other pressure-producing systems.
The regulations related to backflow and cross-connections include the Water Utility Bylaw, the National Plumbing Code and the Alberta Amendments to the National Plumbing Code.
Why do cross connection control devices need to be tested?
Cross-connection control devices have internal seals, springs and moving parts that are subject to fouling, wear or fatigue; therefore, all cross-connection control devices have to be tested to ensure they are functioning properly.
Source: The City of Calgary's Cross Connection website.
Direct Link: http://www.calgary.ca/UEP/Water/Pages/Drinking-water/Prevent-water-contamination/Cross-Connection.aspx