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Backflow Prevention for Commercial and Multi-Family Customers

Backflow Prevention for Commercial and Multi-Family Customers

General Compliance Information

In accordance with Regulation 11 - Section 11.39 pdf of the Colorado Primary Drinking Water Regulations pdf and the Colorado Department of Public Health and Environment, all properties listed below must comply with the state regulation for the installation and annual testing of backflow prevention assemblies. 

There is no "grandfather clause" associated with this regulation, meaning that all existing and all newly constructed properties have to install and test backflow prevention assemblies as needed. View information on installation criteria pdf and/or which backflow prevention assemblies are required to be installed and tested annually. City staff may need to survey properties to determine whether cross-connections are present, what the degree of hazard is or if approved assemblies are installed in proper locations.

Multi-Family Customers

Multi-family properties include 2 or more separate dwelling units served by one meter connection. Multi-family properties generally must comply with backflow prevention installation and annual testing requirements—similar to commercial properties.

  • Small Multi-Family Property Exemptions - Small multi-family properties with 8 units or less may qualify for an exemption from the city’s backflow prevention requirements (installation and annual testing). To qualify, properties must meet all of the criteria listed on the Small Multi-Family Exemption Application pdf. The following FAQ’s pdf will help to fill out the application. An Exemption Application must be submitted for each property requesting an exemption. Please be sure to check all boxes on the form and initial next to them to insure your application is approved. Applications can be submitted by mail to 5605 N 63rd St., Boulder, CO 80301, fax: 303-530-1137 or email to [email protected].

Commercial Properties

Unless otherwise permitted by the Backflow Prevention Program all commercial properties must comply with the installation and annual testing of backflow prevention assemblies.

Defining "Containment"

State regulation and the Backflow Prevention Program are, in general, responsible for monitoring the installation and annual testing of "containment" assemblies. To be a true containment assembly, the assembly must be installed after the meter but prior to any plumbing branches. It is possible that two containment assemblies may be required if branches exist such that a single assembly cannot be used.

Other assemblies may be required inside a property by plumbing code. These other assemblies are called "isolation" assemblies because they isolate internal hazards. The Backflow Prevention Program does not track these assemblies unless there is a specific need. However, it is strongly recommended that isolation assemblies are tested annually along with containment assemblies as they can keep water inside the property safe for consumption. Plumbing code may allow some points of isolation to be protected by devices (non-testable assemblies) such as dual checks.

If it is determined that a specific isolation assembly is to be tracked, the Backflow Prevention Program will require annual testing of both the containment assembly and the specific isolation assembly. If true containment cannot be achieved, the Program Coordinator will determine if isolation assemblies can be tested instead of a single containment assembly. However, whenever possible, containment will be required.


Email Backflow Prevention or call 303-413-7401.