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Backflow Prevention

Nogales Water is committed to delivering safe, high-quality water to our customers. Our extensive water quality program operates 24 hours a day, 365 days a year, to ensure that the water delivered to our customers is kept free from harmful contaminants.

An important part of our water quality commitment is the backflow prevention program. When a water line is connected to equipment containing a no potable substance, this is known as a cross-connection. Contamination may occur when water flows through a cross-connection from a no potable source, such as a sprinkler system or heating and cooling units, into the potable water system. This can happen through a process known as backflow.

There are more than 300 backflow prevention assemblies in use in the Nogales Water service area. The Arizona Department of Environmental Quality requires that each is tested annually. A list of Nogales Water-Approved Certified Testers is available on this website or by calling (520) 285-5733.

The links below lead to more information about Nogales Water's Backflow Prevention program.

Si usted desea información en Español, por favor, llame al (520) 285-5731.

  1. Backflow Prevention Brochure
  2. Blank Backflow Test Report
  3. Backflow Inspection Form

Backflow Prevention FAQ

  • What is backflow

    Nogales Water's system is designed to keep the water flowing from our distribution system to you, the customer. When hydraulic conditions within Nogales Water's system deviate from "normal," the direction of the water flow can be reversed. This creates a backflow condition and the potential for contaminated water entering the distribution system.

  • How can backflow occur?

    Backflow can occur two different ways, by backsiphonage and backpressure.

  • What is backsiphonage?

    When there is a sudden reduction in the water pressure in the distribution system, such as during fire fighting or when a water main breaks, water flow can be reversed. This can create a suction effect, drawing potential contaminates into the potable water distribution system.

  • What is backpressure?

    Backpressure is created when pressure in a non-potable system, such as in a re-circulating system containing soap, acid, or antifreeze, exceeds the pressure in the potable system providing the make-up water. This can force the potable water to reverse its direction of flow through the cross-connection between the two systems. Potential contaminates can then enter the potable water system.

  • How can backflow be prevented?

    Nogales Water recognizes four methods of backflow prevention:

    • Air Gap
    • Double Check Valve Assembly
    • Reduced Pressure Principal Assembly
    • Pressure Vacuum Breaker Assembly

    Nogales Water will determine which type of protection is required based on the degree of hazard that the property represents to the potable water supply.

  • What is a backflow prevention assembly?

    A backflow prevention assembly is an approved, testable assembly which uses valves, in different configurations, to prevent potential contaminates from flowing into the potable water system.

  • How is an assembly approved?

    An approved backflow prevention assembly has gone through an approval process at the Foundation for Hydraulic Research and Cross-Connection Control at the University of Southern California. This is a two-step process consisting of laboratory tests and a twelve-month field test. Only assemblies successfully completing the entire testing procedure are recognized by Nogales Water's approved backflow prevention assemblies.

  • Who is required to have a backflow prevention assembly

    Federal and State law requires that water suppliers protect their water systems from contamination. State regulations exempt single family residences used solely for residential purposes from the requirement to install a backflow prevention assembly. When a determination is made by Nogales Water that the potable water system may be subject to contamination through a backflow condition. Nogales Water makes these decisions on a case-by-case basis. Residential, commercial, and industrial customers, which meet the criteria in City Code #19-57, 19-86 thru 19-97 (Division 5 Backflow Prevention), Ordinance No. 19-J and State Administrative Code R18-4-115 must install and maintain backflow prevention assemblies.

  • How do I know if I need a backflow prevention assembly?

    A Nogales Water Cross Connection Control Specialist (CCCS) will visit your property to do an evaluation for backflow requirements. The CCCS will leave or mail a "Notice of Compliance or Non-Compliance Backflow Prevention Inspection Report." This report will outline the actions you need to take.

  • Is there a general compliance schedule and process?

    Yes. Unless you make other arrangements with Nogales Water, the backflow prevention assembly must be in compliance within 45 days of the date of the initial compliance notification. After 45 days, you will receive a notice informing you that your water service may be discontinued and a non-compliance fee will be assessed to your water bill. If at any time during this process you have a problem meeting this compliance schedule, contact Nogales Water at (520) 285-5731.

  • My property is served with reclaimed water. Do I need backflow protection?

    At this time Nogales Water does not use reclaimed water. However, customers who may receive reclaimed water must install a reduced pressure backflow prevention assembly (RPA) on all potable water service connections to the property.

  • Who can install a backflow prevention

    The installation of the backflow prevention assembly may be done by a property owner/occupant (single family residents only), licensed contractor, or a government agency, subject to the rules and statutes of the Arizona Registrar of Contractors. Permits are required to install or replace these assemblies.

  • If I have questions about backflow prevention, who do I contact?

    Nogales Water Department


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City of Nogales

Nogales, AZ is a great little place to be and is where you’re among friends.

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