FREQUENTLY ASKED QUESTIONS RELATING TO CROSS CONNECTION CONTROL
Back-siphonage is the reversal of normal flow in a system caused by a negative pressure (vacuum or partial vacuum) in the supply piping.
Back-siphonage can be created when there is interruption of the water supply due to nearby fire-fighting, repairs or breaks in water supply mains, etc.
Backpressure -backflow is the reversal of normal flow in a system due to an increase in the downstream pressure above that of the supply pressure.
Back pressure-backflow is caused whenever the downstream pressure exceeds the supply pressure which is possible in installations such as heating systems, elevated tanks, and pressure producing systems. An example would be a hot water boiler operating under pressure coinciding with a reduction or loss of water pressure below the operation boiler pressure. The backflow condition would cause the contaminated boiler water to flow into the potable water supply.
A cross connection is a piping arrangement which allows the potable water supply to be connected to a contaminant source. The most common example is a garden hose attached to a hose bibb with the end of the hose connected to a pesticide sprayer. A drop in water pressure can cause these chemicals to be pulled back into the water supply (backflow), contaminating a building or even a neighbourhood. The contaminant then poses a risk for anyone using the water for drinking, cooking, bathing, or other purposes.
The purpose of a hose bibb is to permit easy attachment of a hose for outside watering purposes. However, a garden hose can be extremely hazardous because they are left submerged in swimming pools, laying in elevated locations watering shrubs, attached to chemical sprayers, etc.
A hose bibb vacuum breaker should be installed on every hose bibb to isolate garden hose applications thus protecting the potable water supply from contamination.
A Cross Connection Control Program is a cooperative effort between plumbing and health officials, water purveyors, property owners and certified testers to establish and administer guidelines for controlling cross connections and implementing means to ensure their enforcement so that the public potable water supply will be protected. The elements of a program define the type of protection required, the responsibility for the administration and enforcement, and a public education and communications plan.
Pollution of the water supply does not constitute an actual health hazard, although the quality of the water is impaired with respect to taste, odor or utility. Contamination of the water supply, however, does constitute an actual health hazard: the consumer being subjected to potentially lethal water borne disease or illness.
The degree of hazard is a commonly used phrase utilized in cross connection programs and is simply a determination on whether the substance in the non-potable system is toxic (health hazard) or non-toxic (non-health hazard). There are three degrees of hazard; severe, moderate and minor. For more information on hazard classification refer to the cross connection manual.
Toxic substance is any liquid, solid or gas, which when introduced into the water supply creates, or may create a danger to health and well-being of the consumer. A non-toxic substance is any substance that may create a non-health hazard, is a nuisance or is aesthetically objectionable. Backflow prevention devices must be selected in accordance with the type of connection and degree of hazard.
Yes, to cause a situation that has the potential to harm the health and well being of your family, co-workers, or neighbours, should be a concern to us all. A cross connection in a home, place of business is a danger to those in the surrounding community. You have a legal and moral responsibility to ensure that our drinking water supply is safe. If you need to know more about Cross Connection control contact a Committee Member near you.
Yes. The following is just one of a number of incidents that have occurred in the last number of years. The incident began after an 8 inch water main, broke and was being repaired. While repairing the break one workman suffered leg burns from a chemical in the water and required medical treatment. Investigations into the cause of the problem led to a possible source of the contamination from a nearby chemical company that distributes chemicals such as sodium hydroxide. The sodium hydroxide is brought to the plant in liquid form in bulk tanker trucks and is transferred to a holding tank and then pumped into drums. When the water main broke, a truck driver was adding water to the bottom of the tanker truck instead of the top, and the sodium hydroxide back-siphoned into the water main.
The National Plumbing Code of Canada, addresses and prohibits any connection whereby potable and non-potable water could mix. The National Plumbing Code states: ìA non-potable water system shall not be connected to a potable water system.î The National Plumbing Code also states: ìBackflow preventers shall be selected and installed in conformance with CAN/CSA-B64.10, ìManual for the Selection and Installation of Backflow Prevention Devices.
Numerous applicable standards are in place to ensure backflow prevention devices meet acceptable standards, they include CSA, AWWA, ASSE, ANSI, & IAPMO
Yes, testing is a requirement of many provincial cross connection control programs, as well as some provincial plumbing codes, and is necessary to ensure that the assembly is working properly. Test cocks are provided on all units to facilitate field testing. Testing information is provided by the manufacturer of the backflow prevention device.
Because of the growing number of serious residential backflow cases, many water purveyors are now requiring the installation of approved dual check valve backflow preventers at residential water meters.
Yes, essentially all backflow preventers cause some degree of pressure loss but other than the reduced pressure assembly the pressure drop is not significant. The typical pressure drop across a reduced pressure assembly ranges from approximately 6 to 13 psi depending the on size and make of the unit.
Any plumbing alteration related to the installation of a backflow preventer will require a plumbing permit.
The AWWA CANADIAN CROSS CONNECTION CONTROL MANUAL, CAN/CSA-B64.10 B64.10.1, (Selection and installation of backflow preventers/Maintenance and field testing of backflow preventers) EPA's Cross Connection Control Manual, and AWWA's M14 Manual are excellent reference manuals for establishing a cross connection control program or for further information on cross connection control.
The five basic protection system/devices are: Air Gap, Atmospheric Vacuum Breaker, Pressure Vacuum Breakers, Double Check Valve Assembly and Reduced Pressure Backflow Preventers.
Air Gap is the physical separation of the potable and non-potable system by an air space. The vertical distance between the supply pipe and the flood level rim should be two times the diameter of the supply pipe, but never less that 1". Air gaps are frequently used on wash basins and industrial processing applications.
Atmospheric Vacuum Breakers may be used only on connections to a non-potable system where the vacuum breaker is not subjected to back -pressure and must be installed on the discharge side of the last control valve and above the usage point. A Atmospheric Vacuum Breaker it not to be used under continuous pressure. Typical applications for an Atmospheric Vacuum Breaker are lawn sprinkler systems and dishwashers.
Hose bibbs installed outside a building, inside a garage, or in an area where there is an identifiable risk of contamination must be protected by a HCVB. Examples of ìidentifiable riskî include laundry sinks, mop sinks, or any other place where garden hose and chemical could be in the same area. Hose bibs that are used to connect appliances (like clothes washers) that already have internal back flow protection do not require a HCVB.
Pressure Vacuum Breakers may be used as protection on connections to all types of non-potable systems where they are not subject to back-pressure. These units must be installed above the usage point and may be used under continuous supply pressure. The applications for a Pressure Vacuum Breaker are similar to the Atmospheric Vacuum Breaker with the exception that they may be used under continuous pressure.
A Double Check Valve Assembly may be used as protection of all direct connections through which any substance might enter the potable water system in a concentration which would constitute a nuisance or be aesthetically objectionable, such as air, steam, food, or other material which does not constitute a health hazard. The Double Check Valve Assembly is used where the degree of hazard is low or moderate.
A Reduced Pressure Principal Backflow Assembly may be used on all direct connections which may be subject to backpressure or back-siphonage, and where there is the possibility of contamination that constitute a potential health hazard. A Reduced Pressure Principle Backflow Preventer is used whenever the non-potable source is more of a contaminate such as boiler feed lines. The Reduced Pressure Principal Backflow Assembly is used where the degree of hazard is severe.
A strainer will protect the check valves of a backflow preventer from fouling due to foreign matter and debris which may be flowing through the line. This not only protects the assembly but eliminates nuisance fouling and subsequent maintenance and shutdown. The use of a strainer with a water pressure reducing valve has been an accepted practice for years. Strainers should not be used in fire protection systems unless approved by the authority having jurisdiction.