A cross connection is a piping arrangement that allows a potable water system to be connected to a source of potential pollution or contamination. It's very important to protect against cross connections in order to prevent backflow into potable water. Ultimately, backflow can cause contamination of an entire public water supply, posing a risk for anyone using that water for drinking, cooking, bathing or any other purposes.
If there's an incident resulting in contamination of public drinking water (due to improper or unprotected plumbing connections causing backflow), the owner responsible or occupant of the property can be held responsible for damages.
What is backflow?
Backflow is the reverse flow of water and/or other substances entering into the drinking water supply from any source other than the water distribution pipes.
There are two types of backflow:
- Back siphonage: this type of backflow occurs when there is a reduction of pressure in the water distribution system (e.g., a water main break, a shutdown for repair, or a high demand for water due to firefighting).
- Back pressure: this type of backflow occurs when there is greater pressure from a premise source other than that supplied from the water distribution system (e.g., a pump for a pond or pool, an irrigation system).
How do I prevent backflow?
In order to comply with Halifax Water’s Rules and Regulations [PDF], as approved by the Nova Scotia Utility and Review Board, property owners must do the following to prevent backflow:
- remove any unnecessary cross connections and isolate your water system from the public system
- protect cross connections that can't be eliminated by attaching an approved backflow prevention device or assembly
- ensure all backflow preventers are tested annually by a certified tester
Backflow prevention device selection and installation
As a condition of connecting to the water supply, the backflow prevention device is required on new industrial, commercial, institutional (ICI), and multi-residential (MR) domestic and sprinkler services at time of meter installation and service activation.
Halifax Water has a retrofit program in place to phase in the required backflow prevention device installation on existing industrial, commercial, institutional (ICI), and multi-residential (MR) domestic services.
The installation and maintenance of backflow prevention devices installed on domestic and sprinkler service lines ensures that potential contaminants will not flow from a premises back into the distribution system. The type of backflow prevention which should be installed is based on how hazardous it could be to the public drinking water:
Severe degree of hazard