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).

Plumbing Codes

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.

Hose Connections

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.


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.

Other Businesses

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
  • Hospitals
  • Industrial Manufacturers
  • Laundries
  • Medical and Dental Clinics
  • Veterinary Facilities

Types of Backflow Prevention Assemblies

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