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Prevent water contamination

The City of Calgary is committed to providing safe reliable drinking water; however, safeguarding drinking water is everyone's responsibility. To protect drinking water from contamination, Water Services runs the Cross Connection Control program.

How can water be contaminated?

Under normal conditions, water is delivered from The City's water supply to citizens for use in their home. Water contamination can happen when backflow occurs due to an unprotected cross connection within a home's plumbing.

What is backflow?
Backflow takes place when water flow reverses due to back siphonage or back pressure.

Back-siphonage may be caused by reduction of supply pressure or when water supply is interrupted. Here are a few examples:

  • When a watermain is shut off for repairs
  • When internal plumbing is shut off for on-site repairs
  • When there is high water demand (i.e., fire fighting, high home water use)
  • When there are different elevations (i.e., elevated piping, hilly landscape)

Back-pressure can arises from any water system that operates at a higher pressure than the supply pressure such as booster pumps, high-rise buildings, thermal expansion, or high pressure boilers.

What is a cross connection?

A cross connection is any temporary, permanent or potential water connection between a potable (drinking) water system and any source containing non-potable water or any other substance from which backflow may occur. Improper plumbing and/or cross connections can contaminate the public drinking water supply.

City Council amended theWater Utility Bylaw​​ ​​to control cross connections through the installation of backflow protection, and mandated the annual testing and maintenance of cross connection control devices. 

Responsibilities for commercial customers and businesses

Industrial, Commercial, and Institutional customers are required to have a cross connection control device installed on their incoming water service at the water meter location. This device must be tested at the time of installation, and then annually by a certified tester.

Please note: We advise customers to use a journeyman plumber, who is certified in cross connection control, to conduct an on-site hazard assessment survey. This will eliminate or provide backflow protection against any unprotected cross connections on your property.

For more information, view theindustrial cross connections brochure.

Responsibilities for residential customers and homeowners

Homeowners must ensure no cross connections exist on their property that could contaminate their water supply. There are several ways to reduce the risk of contamination:

Never place the end of a hose where contaminates could siphon back into your drinking water. Some examples include: a bath tub or spa, wading pool, fish tank, water conditioner, laundry sink and pail or floor drain. Additionally, leave at least a one-inch gap between the end of your hose and any source of contamination.

When using a fertilizer or pesticide sprayer with your garden hose, attach a Hose Connection Vacuum Breaker (HCVB) on your home's outdoor taps. HCVBs are available at retail plumbing suppliers and building material suppliers.

If your home has an in-ground irrigation, you must protect your home's drinking water by installing a minimum of a Double Check Valve Assembly (DCVA) on the water supply to your irrigation system. DCVAs are available at retail irrigation equipment suppliers, plumbing suppliers and building material suppliers.

Heating boiler
If your home has a heating boiler, then a cross connection control device must be installed on the water supply to isolate the heating boiler. The type of device utilized would depend on whether chemicals (anti-freeze solutions, corrosion inhibitors, and oxygen scavengers, etc.) have been added to your home boiler.

Please note: We advise homeowners to have a journeyman plumber, who is certified in cross connection control, eliminate any cross connections on your property. Please check the Calgary yellow pages for a listing of certified plumbers.

For more information, view theresidential cross connections brochure.​​​