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Backflow Prevention

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General Information

The City of Longmont strives to protect our water system from contamination that could diminish our water quality. By installing backflow devices, the possibility of contaminated water returning to the distribution lines is prevented. The City realized the importance of a backflow prevention program and was one of the first water suppliers to start such a program 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. Now, over 3,000 devices have been installed.

The Colorado Department of Public Health and Environment drinking water regulations for backflow prevention and cross-connection control (Colorado Primary Drinking Water Regulations, 5 CCR 1002-11, Section 11.39) help protect the public system from contamination from a backflow event and protect the drinking water quality.

Types of Backflow

Backflow events are the reverse flow of water through the system. This can occur due to back pressure from the source or negative pressure in the system.  

Backsiphonage: Negative pressure in the city’s water system can draw in water from a private water system. Negative pressure in the City’s water system can be caused by water main breaks, fire hydrant flushing, or fire fighting.

Backpressure: If pressure in the private water system exceeds the city's water system pressure, it can force water from the private system into the city's system. This is usually caused by a privately owned pump used to increase pressure inside a single structure.

Types of Cross-Connections

Cross-connection is a term used by the plumbing and water supply industry to describe a physical connection that could allow a contaminant to be drawn or pushed back into the public water system during a backflow event.

Domestic: Domestic service lines are lines that feed the general use of the facility, typically for use in a building. The domestic service line and subsequent plumbing within the building are a private water system, owned and maintained by the property owner. There can be a variety of cross-connections off of a domestic service line, such as permanent swimming pools, industrial water using equipment, and boilers.

Irrigation: Some irrigation lines are tapped directly off of the Public Water Main. In these cases the only cross-connection for this service connection is the irrigation system. Sometimes the irrigation line branches off of the domestic service connection. In this case, the irrigation system is evaluated as one section of the domestic service connection.

Fire Suppression System: Many times fire suppression systems are tapped directly off of the Public Water Main. In some cases, the domestic service line branches off of the fire suppression system service line. Fire suppression systems are a cross-connection for a couple of reasons. First, there may be chemicals added to the fire suppression system that need to be controlled. Second, water in some types of fire suppression systems can be stagnant, allowing bacteria to grow.

Protection Through Containment & Isolation Assemblies

The City of Longmont’s Backflow Prevention and Cross-Connection Control Program mainly revolves around containment assemblies (or devices). This ensures the protection of the drinking water within the public water system. The responsibility for protecting the safety of our public water system belongs to both the water utility and the consumer. There may be cases where, in addition to the containment assemblies, isolation assemblies are used to protect the drinking water quality within the private water system. In limited circumstances and with adequate justification, the City will allow isolation assemblies for compliance with the Backflow Prevention and Cross-Connection Control Program.

Containment: A backflow assembly on the incoming line or service line is containment. The device is after the water meter, but before any branches or connections to the service line.

Isolation: A backflow assembly after branches or connections to the service line. Isolation assemblies are used to protect the drinking water quality within the private water system. 

Types of Control

Assembly (Device): Backflow Prevention Assemblies are mechanical assemblies (devices) installed on the water line to prevent a backflow event. Assemblies are testable and require at least annual testing; those test results must be reported to the City.

Method: Backflow Prevention Methods are methods (such as air gaps) or non-testable devices. Methods are required to be inspected at least annually; those inspection results must be reported to the City.

Learn more about the different types of backflow assemblies and methods >


Frequently Asked Questions

Expand/Contract Questions and Answers

  • How do I know if I have a backflow device and where is it located?

  • How do I submit my backflow test report?

  • How does the City track backflow device inspections?

  • How much does a backflow device test cost?

  • Who can test my backflow device?

  • Who mandated the backflow prevention program? If the state requires this, why don't we follow their program?

  • Who owns the backflow device?

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