What is Backflow?

Backflow is a flow of solid, liquid or gas from any source opposite to the normal direction of flow, back into the potable water supply or system.

There are two types of backflow: 1) backsiphonage and 2) backpressure.

Backsiphonage is caused by negative pressure in the supply piping system. Some common causes of backsiphonage are as follows:

  • High velocity in pipelines
  • Line repair or a break that is lower than a service point
  • Lowered main pressure due to high water withdrawal rate, such as fire fighting or water main flushing
  • Reduced supply pressure on the suction side of a booster pump

Backpressure is caused whenever a potable system is connected to a non-potable supply operating under a higher pressure by means of a pump, boiler, etc. There is a high risk that the non-potable water may be forced into the potable system whenever these interconnections are not properly protected.

There are several backflow prevention assemblies that are used to protect backpressure and backsiphonage incidents from occurring.

How can we prevent backflow situations?

Installing and preventing backflow situations is critical. Many people can be subject to contamination without even realizing the problem. Education is the key to prevention. Water purveyors and certified CCC testers can stay informed about new devices and assemblies available to prevent backflow and backpressure incidents. They should know how and when to use the prevention assemblies and the devices available today. CCC programs can be put in place by water purveyors such as municipalities to mandate the proper installation and maintenance and testing of backflow prevention devices.

Click here to learn more about Backflow testing.
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Island Backflow Testing 
John Mason 
Email: backflowguy@shaw.ca