Cross Connection Rule

Cross Connection and Backflow in Montana

This information applies to Public Water Systems in Montana and consists of definitions and frequently asked questions regarding cross connections and backflow.

What is cross connection?

A cross connection is a connection between a potable water system and any other liquid, or by Montana definition MCA 75-6-102-“Cross-connection” means a connection between a public water supply system and another water supply system, either public or private, or a wastewater or sewer line or other potential source of contamination…

What is a backflow?

Backflow means the undesirable reversal of water flow or the reversal of water flow containing other liquids gases or other substances from a connected source that flows into the distribution pipes of the public water supply system.

Why do public water suppliers need to control cross connections and protect their systems against backflow?

Backflow into a public water system can pollute or contaminate the water in that system resulting in water in that system that is unusable or unsafe to drink. Water suppliers have a responsibility to provide water that is safe to drink to their customers. Water suppliers should take reasonable precautions to protect their public water system against backflow and often times this means the use of backflow prevention.

What is backflow prevention?

Backflow prevention is using methods, assemblies or devices to prevent backflow. A basic method of preventing backflow is an air gap, which either eliminates a cross-connection or provides a barrier to backflow. The basic assemblies or devices for preventing backflow are mechanical backflow preventers which provide a physical barrier to backflow.

What is a method?

A method is a plumbing configuration or way to eliminate the cross connection hazard. This is normally accomplished by constructing an air gap which is considered the ultimate backflow protection. This is not always practical and is easily bypassed.

What is an assembly?

An assembly is a mechanism that is able to be tested and repaired in-line, has isolation valves and test ports provided. A list of approved backflow prevention assemblies is published by the FCCCHR (Foundation for Cross Connection Control and Hydraulic Research). The Department can assist with access.

What is a device

A device is generally a self contained mechanism designed to prevent backflow but it is not able to be tested and therefore has some limitations and may not be approved for use by the Department.

How does one choose the correct backflow prevention?

Correctly choosing backflow prevention depends on the degree of hazard of the cross connection. All states agree and adopt this classification of hazards. Low hazards are pollution risks and non-toxic connections, while high hazards are contamination risks and toxic connections. Other rules apply such as, direct or indirect connections, and is the connection subject to backpressure, or is the connection subject to backsiphonage, or is it under continuous use? It is best to contact the Department for help when choosing backflow prevention.

Do I have to test my backflow preventer and how often?

Backflow preventers are mechanical apparatus that are subject to failure due to age, wear, damage, corrosive water and manufacturing flaws therefore it is an industry standard to have all backflow prevention assemblies tested by a certified backflow prevention assembly tester after the initial installation, after repairs of any kind, and at least once annually.

Where can I find a certified backflow prevention assembly tester or how do I become certified?

The Department accepts a person who holds a current certificate issued by a certification program of any state authorizing the person to test backflow prevention assemblies or who holds a current certificate from the American Society of Sanitary Engineers or the American Backflow Prevention Association.  Both entities retain lists of certificate holders.

Does Montana have rules regarding cross connections and backflow?

Yes, Rules regarding Cross Connections and Backflow in Montana are referenced in the Administrative Rules of Montana, Title 17 Chapter 38 Subchapter 3.
Definitions and incorporated standards are referenced in the Definitions and Incorporation by Reference section of ARM 17.38.301 and 17.38.302.
Cross connections on public water supplies are referenced in the Cross Connection: Regulatory Requirements section of ARM 17.38.305.
Cross-Connection Control Programs are referenced in the Voluntary Cross-Connection Control Programs section of ARM 17.38.310.

How does the new Lead Free Law affect Backflow Prevention?

The Reduction of Lead in Drinking Water Act (42 USC 300G) requires that for manufacture, supply, new installs, and replacement, any valve, fitting, or fixture coming in contact with potable water must meet the requirement of having weighted average lead content of less than 0.25 percent.

“Do I need to go out and find and replace all system components built before 2014 that allowed for up to 8% lead?” The answer is no, but when components fail and/or need replacement they need to be replaced with products meeting the new lead-free definition of 0.25%.


Air Gap

Atmospheric Vacuum Breaker

Double Check Valve

Hose Bibb Vacuum Breaker

Pressure Vacuum Breaker

Reduced Pressure Assembly

Who can I contact for more information?

Karl Carlson, Montana DEQ Field Inspector and Water Quality Specialist
Phone:(406) 247-4444 E-mail:
Billings, Montana

Greg Butts, Montana DEQ Field Services Supervisor and Water Quality Specialist
Phone: (406) 755-8967 E-mail:
Kalispell, Montana