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Backflow Prevention Program

General Information

The City of Longmont Public Works & Natural Resources Department strives to protect our water system from water of a lesser quality. The City realized the importance of a backflow prevention program and was one of the first water suppliers to start one in April, 1984. At that time, there were less than 100 backflow devices installed in the City and less than 100 testers in the state. Since that time, approximately 3,000 commercial and multi-family devices have been installed as well as over 6,000 residential sprinkler system devices.

In 2000, the Water Utilities, through Strategic Planning, was recommended to outsource the backflow program based upon industry standards and best management practices. In addition, the Department contracted for a rate and fee study, which also recommended changing the program from being performed by the City to one where individual property owners are responsible for the testing and repair, using the private sector and the City administering the program. Based on these two recommendations and the on-going backlog of work on this program, the Department is recommending the change to the program.

Quick Links

Types of Backflows

Types of Backflow Devices

Frequently Asked Questions

Contact Information

Utility Operations
375 Airport Road
Phone (303) 651-8467


Any plumbing connection between the city's water lines and a private water system. These include sprinkler systems, fire systems and domestic water connections.

A backflow device on the incoming line or service is containment. The device is after the water meter, but before any branches or connections to the service line. Containment devices have been installed on service lines of multi-family and commercial accounts since 1984. The State of Colorado regulations require containment devices be tested at least annually.

A backflow device installed on a residential lawn sprinkler system is an example of an isolation device. This device prevents lawn sprinkler water from getting back into the home. Plumbing codes may not require isolation devices to be tested on a set frequency. The Colorado Health Department has stated the frequency for testing isolation lawn devices should be set by local authority.



1. Backsiphonage. A negative pressure that can be caused by water main breaks, fire hydrant flushing or fire fighting. Backsiphonage can draw all the water from a private water system. If this water is used for boiler's, sprinkler systems etc. it could contain contaminated water.

2. Backpressure. This is caused by the pressure in the private water system exceeding the city's water system usually caused by a privately owned pump used to increase pressure inside a single structure. This causes water to be forced back into the city's system.


1. Air Gap
Used mainly on tanks and faucets, it is a gap between the pipe and the container.

-The gap needs to be a minimum 2 times the supply pipe diameter.

2. Atmospheric Vacuum Breaker

photo of atmospheric vacuum breaker

Used mainly on lawn irrigation systems. It has an air inlet valve that will drop to draw in air thus preventing sprinkler system water from entering the City's water mains.

-Not under continuous pressure for more than 12 hours
-No downstream valves
-No backpressure
-6" above high point of use

3. Pressure Vacuum Breaker

photo of pressure vacuum breaker


Used mainly on lawn irrigation systems. It has a one way check and a spring loaded air inlet valve that closes when City water main pressure drops.

-No backpressure
-12" above high point of use
-Protect from freezing

4. Double Check Assembly

photo of double check assembly



Operates similar to a Pressure Vacuum Breaker. Used on low hazard buildings and on fire lines.

5. Reduced Pressure Principle Assembly

photo of reduced pressure principle assembly



Used on high hazard buildings and is a combination of check valves and an air inlet allowing water from the private system to vent when City pressure drops.

By installing backflow devices, the possibility of contaminated water returning to the distribution lines is prevented.

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Frequently Asked Questions

Are all residential homes required to have backflow devices?
Those residential homes that have sprinkler systems are required to have backflow devices on those systems.

How much will the inspections/maintenance cost?
A survey of prospective certified testers was done and the average cost was $50 to $100.

Will there be a list of recommended certified testers available to us? Where can we view this list.
Yes, a list of certified testers will be sent along with a letter reminding the homeowner to obtain the test. We also anticipate having it available on our web site.

As more information becomes available and when this issue goes to City Council to be voted on how will we be notified or informed?
We have developed a list of citizens interested in receiving updated information. Anyone interested in being placed on this list, please call Alan Platt at 303-651-8467. The City web site will also be updated periodically as new information becomes available.

Who will take ownership of the backflow device if this program goes into affect?
The ownership of the device will revert to the property owner.

Who mandated the backflow program? If the state requires this, why don't we follow their program?
The State of Colorado and the International Plumbing Code mandates that water suppliers develop and maintain a backflow program. Neither entities have developed specific programs but the State has outlined testing requirements for containment devices.

How will the City track the inspections?
Currently, through a data base system, the Water Department tracks backflow devices, test results will be entered into this data base system.

How do I know if I have a backflow device and where is it located?
Please call 303-651-8468 and a water representative will help you.

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Utility Operations|Water Utilities|Public Works & Natural Resources|City of Longmont
This site was updated August 16, 2013
City of Longmont Public Works & Natural Resources
Utility Operations