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Cross-Connection and Backflow Prevention
Cross-connection and backflow are two issues that may cause the contamination or pollution of potable water, which is water that is fit for drinking, cooking and household uses.
- Contamination is the introduction or presence of any foreign substance in a drinking water system that could or does make the water hazardous to human health.
- Pollution is the introduction or presence of any foreign substance in a drinking water system that could or does change the taste, odor or color of the water and weakens its usefulness but is not hazardous to human health.
Environmental Protection Agency Cross-Connection Control Manual
View the Environmental Protection Agency (EPA) Cross-Connection Control Manual for more information regarding:
- Additional examples of assemblies and devices.
- The principles of water pressure and backflow.
- The types of problems that can and have been caused by cross-connections and backflow.
Have you ever connected a garden sprayer to the end of a hose to fertilize your vegetables or flowers? Have you ever stuck the end of a garden hose into your car’s radiator or connected it to the heater hoses to flush the radiator? Or, have you ever placed the hose under the water’s surface in a swimming pool and left it on? Many of us do. However, doing any of these poses a risk of contaminating your home’s drinking water with chemicals that can cause serious health concerns if swallowed.
A cross-connection is any existing or possible interconnection between a drinking water system and any other system that contains a substance of unknown or uncertain quality. It also is the link that can bring two systems together. The most common cross-connection is an outside hose faucet, typically called a hose bib or sillcock. Use these plumbing fixtures for connecting hoses that you use for various purposes such as watering your gardens, flowers and lawns.
Cross-connection control is the methods, practices and procedures used to prevent contamination or pollution of drinking water from backflow through cross connections. It ensures that your drinking water remains safe from bacteria, chemicals and other substances that may enter the water from unknown or improperly maintained sources because of abnormal pressure changes. A cross-connection control program is a written plan that:
- Detects, monitors and manages cross-connections.
- Implements the procedures and practices necessary to ensure safe drinking water to comply with government rules and regulations.
Backflow is the reverse flow of water or other substances in pipes, typically caused by unusual and irregular changes in pressure.
- Back-siphonage is the backward flow of water or other substances from one system to another because of a decrease in pressure. The pressure decrease causes the water or substance to draw or siphon backward to the point of lowest pressure, such as at a suddenly-opened valve or hydrant, or at a break in a pipe or a water main.
- Backpressure is the backward flow of water or other substances from one system to another because of an increase in pressure. The pressure increase causes the water or substance to push backward suddenly or over time by a pump, an increase in temperature or because of changes in height (pressure increases as water rises).
Prevent backflow by avoiding the reverse flow of an unwanted substance into the drinking water with special plumbing methods, devices and practices. Prevent backflow by using a physical means or mechanical device designed and built specifically to prevent backflow.
Approved backflow prevention methods, assemblies and devices are a physical means or mechanical device that a nationally recognized laboratory, organization or institute tested and approved. These organizations include:
- The American Society of Sanitary Engineering
- Factory Mutual
- The Foundation for Cross-Connection Control and Hydraulic Research
- Underwriters Laboratory
Backflow Prevention Assemblies
If you have a toilet with a tank on the back in your home or business, it contains a valve to fill the tank every time you flush. The fill valve, or ballcock, is equipped with an approved backflow prevention device that prevents any water in the tank from being siphoned back into the pipes of your house (anti-siphon).
The types of backflow prevention assemblies installed at these locations can range in size from 3/4-inch to 10 inches in diameter and cost anywhere from a hundred to several thousand dollars to purchase, install and maintain. Other types of backflow prevention assemblies include:
- Double check valve
- Pressure vacuum breaker
- Reduced pressure zone
Plumbing codes require all water outlets to be equipped with a backflow prevention method or device to prevent contamination or pollution of the drinking water. Therefore, all sinks have a space between the end of the faucet and the flood level of the sink, called an air gap. Some sinks typically found in commercial businesses, such as a mop sink, are equipped with a backflow prevention device called an atmospheric vacuum breaker installed on the faucet.
All hose bibs (hose connections), sometimes called sillcocks, are required by code to have a special backflow prevention device installed called a hose connection vacuum breaker. This device prevents water in the hose from flowing backward into the pipes of your house.
Underground Lawn and Garden Irrigation Systems
All underground lawn and garden irrigation systems are required to have backflow prevention assemblies installed and routinely maintained. State and local regulations and codes require such assemblies to be tested at the time they are installed and yearly thereafter, as well as any time they are repaired, relocated or replaced. View the guide to selecting, installing and maintaining backflow preventers in residential irrigation systems (PDF).
In restaurants, beverage dispensing equipment is required to have specialized backflow prevention devices installed to prevent carbon dioxide gas and carbonated water from mixing with copper piping.
In other types of commercial and industrial businesses, it is necessary to ensure the safety of Chesterfield County’s drinking water by requiring the installation of backflow prevention assemblies in the main water-service line to certain types of buildings, such as:
- Car Washes
- Chemical and Petroleum Processing and Storage Facilities
- Funeral Homes
- Industrial Manufacturers
- Medical and Dental Clinics
- Veterinary Facilities
View the guide to the selection, installation and maintenance of backflow prevention assemblies and devices for general commercial and industrial applications (PDF).
Backflow Prevention Assembly Performance Tests
A performance test is done to check if the assembly continues to operate as designed and continues to protect against backflow. A specialized test instrument equipped with a large pressure gauge is connected to the backflow prevention assembly with three separate high-pressure hoses that are attached in various techniques to measure the differences in pressure under certain conditions.
The test must be performed by someone who holds a current certification as a backflow prevention device worker issued by the Virginia Department of Professional and Occupational Regulation. The certification ensures that the tester is specially trained, experienced and has successfully completed an examination that tests their competency in the subject of cross connection control and backflow prevention.
There is no control over the cost of the test. Certified testers and businesses set their own prices, which are typically controlled by the current market. The owner (property owner, building owner, tenant or homeowner) is responsible for maintenance of the backflow prevention assembly at his or her own expense.
At the time the test is conducted by the certified tester, they will complete a backflow prevention assembly test report form (PDF), provide a copy to the owner, and either the owner or the certified tester must send Chesterfield County a copy of the completed report for the county’s records by emailing Utilities, faxing to 804-751-4437 or mailing to:
Cross Connection Control Coordinator
Chesterfield County Department of Utilities
P.O. Box 608
Chesterfield, VA 23832-0009