Frequently Asked Questions

What is backflow?

Backflow refers to the undesirable reverse flow of fluids, chemicals or any other foreign material through a cross-connection and into the public water system or customer's potable water system. The two types of backflow include backpressure (caused by pumps, piping systems elevation or thermal expansion from a heat source) and backsiphonage (caused by a loss of pressure in the drinking water system).

What is a cross-connection?

A cross-connection is any temporary or permanent connection between a public water system and any source or system containing non-potable water. Common cross-connections include:

  • Private wells – Where the private well is connected to a service line receiving water from a public water supply. The untreated water could be pumped into the potable water supply, which serves the home and the public water system.
  • Lawn sprinkler systems – Where the stagnant/contaminated water from the sprinkler system could be drawn into the drinkable water supply for your home.
  • Commercial and industrial equipment connected for cooling or processing water.

What is back-siphonage?

Backsiphonage is backflow caused by negative pressure (i.e. vacuum or partial vacuum) in a public water system or a customer's potable water system. The effect is similar to drinking water through a straw. Backsiphonage can occur when there is a stoppage of water supply due to nearby fire-fighting, a break in a water main, or other reasons.

Why do water suppliers need to control cross-connections and protect their public water systems against backflow?

Backflow into a public water system can pollute or contaminate the water in that system. Water pollution can reduce the quality of drinking water and water contamination can cause concern for public health if the water is consumed. Water suppliers must take precautions to protect its public water system from potential pollution or contamination.

What is a backflow preventer?

A backflow prevention device or assembly is a mechanism to prevent backflow. The basic means to prevent backflow is an air gap, which either eliminates a cross-connection or provides a barrier from backflow. A mechanical backflow preventer provides a physical barrier to prevent backflow.

Is a permit required to install a backflow preventer?

Yes. A plumbing permit is required for the installation of any backflow prevention device.

Why do backflow prevention devices need to be tested?

Mechanical backflow prevention devices have internal seals, springs, and moving parts that are subject to fouling, wear or fatigue. Also, mechanical backflow preventers and air gaps can be bypassed. Therefore, all backflow prevention devices have to be tested periodically to ensure that they are functioning correctly. Mechanical backflow prevention devices have to be tested with properly calibrated gauge equipment.

How often does the backflow prevention device need to be tested?

Backflow prevention devices must be tested and certified upon installation and at least once every year. The testing and certification must be performed by a licensed backflow tester.

Where can I find licenced backflow testers?

Northumberland County can provide a list of local surveyors and testers, or you can visit the OWWA Ontario Water Works Association Tester List or the American Society of Sanitary Engineers (ASSE) Certified Professionals directory.

Does a lawn irrigation system require a backflow prevention device?

Yes. The potable water supply to lawn irrigation systems should be protected against backflow and potential hazards.

What is considered a potential hazard?

A potential hazard is defined as any possibility of pollutants, contaminants and system or plumbing hazards. For example: fire protection systems, irrigation systems, gasoline refineries and stations, restaurants, hospitals and manufacturers.

What can be done to protect our drinking water at home?

  • DO keep the ends of hoses clear of all possible contaminants.
  • DON'T submerge hoses in buckets, sinks, tubs, pools, ponds etc.
  • DON'T use spray attachments without a backflow prevention device.
  • DO install an approved backflow prevention device on all lawn irrigation systems, swimming pools, water softeners (and many others).
  • DON'T connect waste pipes from water softeners or other treatment systems to the sewer, submerged drain pipes, etc.
  • DO install hose connection vacuum breakers on all unprotected threaded faucets around your home—these devices are inexpensive and are available at hardware stores and home improvement centres.
  • DON'T use a hose to unplug blocked toilets, sewers, etc.
  • DO ensure, when having a backflow prevention device installed that your contractor is qualified.

Who is responsible for the survey of my property, and the installation, testing and maintenance of the backflow prevention devices?

It is up to the property owner to ensure that:

  • the property is surveyed;
  • backflow prevention devices and cross connections are identified;
  • backflow prevention devices are tested at the time of installation and on an annual basis thereafter; and,
  • backflow prevention devices are properly maintained and repaired. If any maintenance or repairs are performed on the device, it must be re-tested.

Where can I get more information about cross-connection control?

  • CAN/CSA-B64.10-11 CAN/CSA-B64.10.1-11 Standard
  • Manual for the Selection and Installation of Backflow Prevention Devices
  • Manual for the Maintenance and Field Testing of Backflow Prevention Devices
  • Ontario Building Code – Part 7 Plumbing
  • EPA’s Cross Connection Control Manual
  • AWWA Canadian Cross Connection Control Manual
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