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Cross-Connection Control and Backflow Prevention Program

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

The Colorado Department of Public Health and Environment regulates drinking water quality and standards. The Colorado Primary Drinking Water Regulations (Regulation 11) outline Denver Water’s requirements for cross-connection control and backflow prevention.

In addition to installing an assembly, the water customer must have the assembly tested upon installation and annually thereafter by a certified backflow prevention assembly tester. All testing must be reported to Denver Water’s Cross-Connection Control office. All test reports must be sent to


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.

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Without Backflow Prevention Assembly

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Without Backflow Prevention Assembly


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 they do not have adequate backflow prevention assemblies installed. There are numerous, well-documented cases in which cross-connections have been responsible for contamination of drinking 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 the reversal of the flow of water once it has passed through the valve.

Like any mechanical device, a backflow prevention assembly requires maintenance and annual testing. There are different types of backflow prevention assemblies required for different uses and different degrees of hazard.

There are no exemptions or grandfathering in of backflow prevention assembly requirements.

Approved backflow prevention assemblies

Backflow prevention assemblies installed within Denver Water’s 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 your backflow prevention assembly manufacturer or the product specification sheets to verify that the assembly is USC-approved. You must also confirm the assembly is approved in the orientation for which it is being installed (horizontal, vertical, etc.).

Types of backflow prevention assemblies

Reduced Pressure Principle Assembly (RP)

An RP is required for most commercial, industrial and some multi-family applications. They can also be used on irrigation systems where a pressure vacuum breaker (PVB) cannot be used.

Installation requirements:

  • Install a minimum of 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 required for fire lines without antifreeze or chemical additives and some residential applications. They are not allowed for irrigation systems.

Installation requirements:

  • Install a minimum of 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 for use on irrigation systems. They have specific installation requirements and are limited in their use. 

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 or irrigation uses. Irrigation systems must be protected with either a reduced pressure principle assembly (RP) or a pressure vacuum breaker (PVB) depending on installation requirements. 

Irrigation backflows

The irrigation backflow testing season is from May to September. Irrigation backflow prevention assemblies must be tested by a certified backflow assembly tester as the water is turned on to ensure proper backflow prevention is in place to protect our drinking water during the irrigation season. Denver Water will send out a testing reminder notice 30 days before the annual test is due.

I received a Suspension of Service and Public Health Hazard Notice due to Denver Water not gaining access to complete a survey.

  • The survey of the water service line is required per State Regulation 11.39 to determine if a backflow is necessary to protect the main drinking water supply from hazards on the property. 
  • Customer must contact Cross Connection Control 303-628-5969 or to schedule an appointment so that Denver Water can complete the survey and to cancel a suspension of service.

I did not receive a backflow letter or notice.

  • Denver Water sends out three notices to both the service address and the backflow contact on record prior to a disconnection of service within a 60-day time frame. Please call Customer Care at 303-893-2444 to provide the backflow contact mailing address.