What is backflow? Backflow occurs when hydraulic conditions within our water distribution system deviate from “normal” and flow reverses, causing pollutants and contaminants to enter the system.

What causes backflow? Backflow is possible in two situations: backsiphonage and backpressure.

What is backsiphonage? When the pressure in the water distribution system drops suddenly (for example, during firefighting or a water main break), flow can reverse. This can create a suction effect, drawing the nonpotable substance into the water system.

What is backpressure? Backpressure is created when the pressure in a nonpotable system — such as a recirculating system containing soap, acid, or antifreeze — exceeds that in the potable system that provides make-up water. This can force the potable water to reverse its flow direction through the cross connection. Nonpotable substances can then enter the potable water system.

How can backflow be prevented? Flagstaff recognizes four methods of backflow prevention: air gap, reduced-pressure principal backflow prevention assembly, pressure vacuum breaker assembly or spill-proof vacuum breaker, and double-check backflow prevention assembly. The City's Cross Connection Control Program will determine which type is required based on the degree of hazard your property represents to the potable water supply.

What is a backflow assembly? A backflow assembly allows one way flow of water, preventing polluted or contaminated water from reversing direction and flowing backward into the City's potable water supply

How is an assembly approved? It goes through an approval process at the Foundation for Hydraulic Research and Cross Connection Control at the University of Southern California. This two-step process consists of laboratory tests and 12 months of field testing. Assemblies successfully completing the entire testing procedure are recognized by the City as approved.

Who is required to have a backflow prevention assembly? This is determined on a case by case basis by the City's Cross Connection Control Program. Backflow assemblies are generally required for commercial and industrial customers where potential for contamination of potable water sources exists. Residents where nonpotable water (such as reclaimed water) is used on site are also required to install backflow assemblies. State regulations exempt single-family residences used solely for residential purposes if there are no hazards present. New facilities must install assemblies in a hot box outside of the building (unless it is for the fire riser — then it can go in the fire riser room with adequate drainage to the sanitary sewer), as close to the water meter as possible. Copies of City Ordinance #7-03-001-0015 and State Administrative Code rule R18-4-215 are available in the City Clerk’s office or from the Industrial Pretreatment Program at (928) 213-2117.

How do I know if I need a backflow prevention assembly? Most backflow requirements begin with the construction plan review and permit process. You will be notified of the need for a backflow prevention assembly after the City's Cross Connection Control Program evaluates your property and your construction plans. You may also be informed of the need for a backflow assembly following an inspection of your existing business. 

Is there a general compliance schedule and process? Yes. Unless you make other arrangements with the Cross Connection Control Program, the backflow prevention assembly must be in compliance within 30 days from the date of the initial notification. You will receive a follow-up notice after 30 days. After 45 days, you will receive a notice informing you that your water service may be discontinued unless you achieve compliance. If at any time during this process you have a problem meeting this schedule, it is extremely important that you contact the Cross Connection Control Program immediately, at (928) 213-2117, to make special arrangements for an extension.

Who can install a backflow prevention assembly? The customer is responsible for installing the backflow prevention assembly. It may be installed by a property owner, plumbing contractor, or a general contractor, subject to the Rules and Statutes of the Arizona Registrar of Contractors. Permits are required to install or replace these assemblies. Permits are issued by Flagstaff's Building Safety Department. Please call (928) 213-2618 for additional information.

Where should a backflow prevention assembly be located? The assembly must be located as close as possible to the water meter service connection, with a heated enclosure, remaining on private property. A variance can be made for indoor installation, but is subject to City approval prior to construction. Contact the Cross Connection Control Program at (928) 213-2117 for information on variances.

Who is responsible for testing and maintaining the backflow assembly? It is the sole responsibility of the customer to ensure that the assembly is always in satisfactory operating condition. The City's Cross Connection Control Program will send a courtesy notice when annual testing is due. You are required to schedule testing with a certified tester, who will submit the results on your behalf. If any repair work or maintenance is performed on the assembly, a certified tester must retest the assembly immediately and submit the results. Contact Jolene Hayes at (928) 213-2117 for instruction on how to submit the backflow prevention assembly test result.

I have multiple testing dates for the backflows at my property. Can I consolidate the dates? Yes, a customer may request a change of the annual test compliance date for any assembly. No compliance date may be changed to be more than 12 months after the most recent test. Please contact Industrial Pretreatment at (928) 213-2177 or pretreatment@flagstaffaz.gov. 

I have an irrigation or fire sprinkler backflow assembly I no longer use. Can I remove it? Yes. You need approval from the Cross Connection Control program prior to the work being scheduled. Proper removal will protect the City's water supply and your internal plumbing. 

BSI Online
List of Approved Assemblies