Important Updates:

The city expands beta to preview its new website and gather feedback. | More Info


The City of Boulder welcomes your feedback. Use our Inquire Boulder customer service tool to tell us what’s on your mind.

  • Boulder Water
  • Your Utility Bill
  • Flood Safety
  • Utilities Projects
  • Wastewater
  • Utilities Division Boards
  • Construction and Travel Impacts

Backflow Prevention Program

Installation and annual testing of backflow prevention assemblies is a state requirement to help protect water quality and public health.

Small Multi-Family Property Exemptions - Small multi-family properties may qualify for an exemption from the city’s backflow prevention requirements. To qualify, properties must meet all of the criteria listed on the Small Multi-Family Exemption Application. Find more information below under "Multi-Family Customers."

Codes & Regulations

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.

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.

Irrigation and Pressure Vacuum Breakers

Pressure vacuum breakers that are currently being used for backflow prevention on dedicated irrigation lines are acceptable as long as the assembly passes annual tests. City of Boulder Design and Construction Standards 5.09(c)(4) states:

Reduced Pressure Assembly Required: All irrigation systems with a separate, metered  service line shall have a reduced pressure principle assembly installed in compliance with all  applicable city regulations and standards.

Therefore, if a pressure vacuum breaker fails and requires replacement it should be replaced with a Reduced Pressure Zone Assembly.

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. 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.


At this time, residential customers/homeowners do not have to comply with the Backflow Prevention Program requirements unless:

  • There is an auxiliary water source on the property;
  • There is a dedicated irrigation line tapped off of the main; or
  • There is another hazard as identified by the Backflow Prevention Program (including the existence of a well on the property).

The Backflow Prevention Program requirements are not meant to contradict building, fire or plumbing codes, which may require a residence to have a backflow prevention assembly like those required on residential sprinkler systems. When backflow prevention assemblies are otherwise required, they must be installed, but will not be tracked by the Backflow Prevention Program.

Backflow Prevention Assembly Testers

How to find a tester

Currently, the Backflow Prevention Program cannot recommend testers nor does the city keep a list of testers.

If you are in need of a tester, you can find one by:

  1. Consulting With Your Current Plumber or Contractor - these professions usually hold their own certification or know someone who can test your assembly. Whomever you select to test your backflow prevention assembly must be certified to do so. Testers must hold a current certification from either The American Backflow Prevention Association, or The American Society of Sanitary Engineers.
  2. Checking Your Assembly - Generally your existing backflow prevention assembly has been tested before and should have a tag from the previous tester that shows the tester's or testing company phone number.
  3. Visiting the Colorado Division of Fire Prevention & Control website if you're looking for someone who can also test assemblies on fire lines. Click on "Fire Suppression Systems" and then on "Backflow Contractors."

How assemblies are tested

Backflow prevention assemblies are tested by certified testers who use gauges to either add or relieve pressure to determine if the internal parts are working properly. This information is recorded on a backflow prevention assembly test report. Testers or owners are required to submit test reports to the Backflow Prevention Program at [email protected].

What test form should be used?

The City of Boulder's Backflow Prevention Program uses a Universal Test Form created, used and accepted by backflow programs across Colorado. Incomplete or incorrectly filled out forms will be returned to the tester.

Passing tests

When the backflow prevention assembly passes the test, the tester must submit a copy to the Backflow Prevention Progam within 10 days from the test date. This information will be recorded by the program and testing will not be required until the following year. Water suppliers, testers and customers must all retain test report records for three years.

Failing tests

Backflow prevention assemblies that fail a test must be repaired and/or replaced immediately. The Backflow Prevention Program must be verbally notified the same day and the failing test should be submitted within three days. If the repair or replacement cannot be made immediately, the Backflow Prevention Program must be notified and a compliance plan must be established.

As a failed backflow prevention assembly test represents a direct cross-connection, failure to repair/replace and test an assembly can result in suspension of water service if the Backflow Prevention Program determines that the cross-connection represents an immediate risk to public health.

Keeping copies of test reports
Regulation 11 - Section 11.39 of the Colorado Primary Drinking Water Regulation states that backflow prevention assembly test reports should be kept for three years by the water supplier, the tester and the customer.

Tester certification information
Backflow prevention assembly testers must be certified by one of two National Certifying Agencies:

  • The American Backflow Prevention Association (ABPA)
  • The American Society of Sanitary Engineers (ASSE)

Both organizations re-test every three years and anyone testing a backflow prevention assembly must have a current certification on the date of the test.



Email Backflow Prevention  or call 303-413-7401.