Backflow

Cheyenne Board of Public Utilities Cross-Connection Control and Backflow Prevention Program protects the public water supply from pollutants and contaminants that could, under certain circumstances be drawn into the public water supply from private properties. 

All new residential, new and existing commercial and industrial domestic, irrigation and fire line services are required to have an approved backflow prevention assembly installed.  Requirements for multi-and single-family residence are assessed based on site hazards.  All customers with an auxiliary water supply, such as a well or pond, are also required to install and maintain backflow prevention assemblies. 

Backflow prevention assemblies must be tested following installation.  Commercial and industrial customers are required to have their backflow prevention devices tested annually by a certified backflow prevention assembly tester.  All testing must be reported to the Cheyenne Board of Public Utilities’ Water Cross Connection Control Office. 

The Wyoming Department of Environmental Quality Chapter 12 regulations outline Cheyenne Board of Public Utilities’ requirements for cross connection control and backflow prevention.   

What is Backflow?

Backflow is the unwanted flow of water or other liquids, mixtures, gasses or substances into the drinking water supply.  There are two main ways backflow can occur: 

Backsiphonage occurs when there is a negative pressure in the water distribution system, which draws the water from a private water system into the public water system.  This can occur at any time, such as during a water main break or during a large firefighting effort. 

Backpressure occurs when the pressure in a private water system exceeds the pressure in the public water distribution lines that can cause normal flow to reverse. A pump used to increase the water pressure within a building’s plumbing system to reach a higher floor might cause this. 

Cross Connections

Cross-connections are actual or potential connections between the public water supply and any other system that could accidentally introduce a contaminant back into the public water supply. 

According to the Environmental Protection Agency, cross-connections can be a serious public health hazard if adequate backflow prevention assemblies are not installed.  There are numerous, well-documented cases in which cross-connections have been responsible for contamination of drink water that, when consumed, caused the spread of sickness or disease.


Backflow Prevention Assemblies

A backflow prevention assembly is a mechanical valve arrangement designed to prevent flow reversal of water once it has passed through the valve. Like any mechanical device, a backflow prevention assembly requires maintenance and annual testing.   

For commercial and industrial services, there are no exemptions for backflow prevention assembly requirements.


Approved Backflow Prevention Assemblies

Backflow prevention assemblies installed within the Board of Public Utilities’ distribution system must be approved by the University of Southern California’s Foundation for Cross-Connection Control and Hydraulic Research, otherwise known as being USC-approved.   

Check with the backflow prevention assembly manufacturer or check the product specification sheets to verify the assembly is USC-approved.  Confirmation is also needed to verify the assembly is approved in the orientation for which it is being installed (horizontal, vertical, etc.). 


Types of Backflow Prevention Assemblies and Approved Uses

Reduced Pressure Principle Assembly (RP) 
An RP is required for most commercial, industrial and some domestic water applications, as well as some irrigation applications. 
Installation requirements: 

  • Install at a minimum - 12 inches off the floor and 12 inches away from a wall. 

  • If the assembly is installed higher than 5 feet off the ground, a platform is required for access and maintenance. 

  • Adequate drainage is required, as there is a potential for discharge from the unit. 

  • Protect from freezing. 

Double Check Valve Assembly (DC) 
A DC is approved for domestic services where no hazard exists and is required for fire lines without antifreeze or chemical additives. They are not allowed for irrigation systems. 
Installation requirements: 

  • Install at a minimum - 12 inches off the floor and 12 inches away from a wall. 

  • If the assembly is installed higher than 5 feet off the ground, a platform is required for access and maintenance. 

Pressure Vacuum Breaker (PVB) 
PVBs are most often used as protection for irrigation systems where installation requirements are met. 
Installation requirements: 

  • Must be installed a minimum of 12 inches above the highest point of use and 12 inches away from a wall. 

  • Cannot be subjected to continuous backpressure. 

Atmospheric Vacuum Breaker (AVB) 
AVBs are generally used as point-of-use devices for a specific, internal plumbing process. Denver Water does not allow AVBs for any type of containment uses. 


(PDF, 114KB)

What can I do to protect against backflow?

Help protect the water supply from backflow by installing one or all the following devices where they are missing: 

Double Check on the domestic water main service in your house. 

High Hazard device (RPZ OR PVB) on your irrigation main line. 

Double Check on your main line for a non-chemical fire suppression. 

High Hazard device on a chemical feed fire suppression. 

Hose Bibb Vacuum Breaker – simple, inexpensive device that can keep water from being sucked through your hose into your house.  Use one when using a hose to spray for bugs, spread fertilizer or push debris out of gutters. 

 The BOPU strongly recommends that everyone install a backflow device on sprinkler systems and in their homes.  Test these devices annually to ensure they are working properly.


Who can test my backflow preventer?