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What is a Cross Connection?
A Cross Connection is any actual or potential connection between a potable water system and any source of pollution or contamination. Bypass arrangements, jumper connections, removable sections, swivel or changeover devices, or any other temporary or permanent connecting arrangements through which backflow may occur are considered to be cross-connections.
What is Backflow?
Backflow is a flowing back or reversal of the normal direction of flow in a piping system. It occurs due to a differential pressure existing between two different points within a continuous fluid system; a fluid of higher pressure flowing to a fluid of lower pressure. Backflow may occur due to either backsiphonage or backpressure.
What is Backsiphonage?
Backsiphonage is caused by negative pressure or reduced pressure in the supply piping. Some common causes of backsiphonage are:
- High velocities in pipe lines
- Line repair or 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 the booster pump
What is Backpressure?
Backpressure may cause backflow to occur whenever a potable water system is connected to a non-potable supply operating at a higher pressure. If these connections are not properly protected, potable, non-potable water or liquids can be forced into the potable water supply system. Some common causes of backpressure are:
- Booster pumps
- Interconnections with another system operated at a higher pressure
- Elevated piping (e.g. 30' above finished grade)
What are the methods of Backflow Prevention?
The control of backflow, whether caused by backsiphonage or backpressure, requires the elimination of the cross connection and the installation of an air gap or a backflow prevention device. Halifax Water recognizes the following three general methods or types of backflow prevention devices used for the prevention of backflow:
How is the type of Backflow Prevention device selected?
Halifax Water will determine which type of protection is required based on the degree of hazard that the premise represents to the potable water supply.
Where are Backflow-Prevention Devices required to be installed?
Halifax Water's Cross Connection Control Program requires all multi residential units (greater than four units), industrial, commercial, and institutional buildings to install a Backflow Prevention Device on their water service lateral. The devices are installed, to provide premises isolation, at the entrance to the building for new sprinkler services and on the customer’s side of the water meter for domestic services.
Who is responsible for the testing and maintenance of the Backflow-Prevention device?
The Customer is responsible to ensure that the BackflowPrevention Device is in satisfactory operating conditions at all times. The Backflow-Prevention Devices must be tested at the time of installation and on an annual basis thereafter. If any maintenance or repairs are performed on the device, the device must be re-tested. Halifax Water will send a notice to the customer advising them when an annual test is required on the device. Attached with this notice will be a list of recognized Backflow Prevention Device Testers. The customer must contact one of these recognized Testers to perform the test and submit the results to Halifax Water.
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