Which Businesses Need a Backflow Assembly in Each Valley City

State law sets the floor. A.R.S. 49-353 tells the state to "require a public water system to implement a specified program to control contamination from backflow, backsiphonage or cross connection," and ADEQ's rule (A.A.C. R18-4-215) says required assemblies are tested at least once a year by a certified tester.

The cities fill in the rest in their water codes: Phoenix Chapter 37, Mesa Title 8 Chapter 1, Scottsdale Chapter 49, Glendale and Tempe Chapter 33, Gilbert Chapter 10. Those chapters protect the city main at your meter, which the codes call service or containment protection. Inside the building, the plumbing code adds protection at each fixture. Most Valley cities enforce the International Plumbing Code: the 2024 edition in Phoenix, Mesa, Tempe, Chandler, Glendale, Surprise and Tolleson, 2021 in Scottsdale, and 2018 in Gilbert and Peoria. Phoenix also allows the 2024 Uniform Plumbing Code.

The lists use four abbreviations, and they're not interchangeable.

• RP (also RPA or RPZ). Reduced pressure principle assembly: two check valves with a relief valve between them that dumps water if pressure goes the wrong way.
• DC (DCVA). Double check valve assembly: two check valves, no relief valve. Allowed only where a backflow would be objectionable but not dangerous to health.
• PVB. Pressure vacuum breaker, mostly for landscape irrigation. It has to sit above the piping it protects; Mesa requires an RPA where a PVB can't be at least 12 inches higher than all downstream plumbing.
• Air gap. Open air between the supply pipe and whatever it fills. At least twice the pipe diameter and never under one inch, in Phoenix's definition.

When a property has two listed uses on one service, Scottsdale and Glendale require the most protective device either use calls for, and Mesa requires an RPA.

Businesses and other non-residential customers on city water. Several lists also name schools, master-metered apartment complexes and construction water services. The codes put the duty on the water customer, and Goodyear's names the property owner or the person using the property.

A house used only as a home is usually outside the containment rules. The state rule and Phoenix's code both exempt single-family homes unless a cross connection is found, though Mesa still requires protection on any dedicated landscape meter, home or business.

If your business isn't named, that isn't a pass. Phoenix, Chandler and Avondale send unlisted cases to the city to judge, and Gilbert's list says "including but not limited to."

At least once a year everywhere, but repair and paperwork deadlines range from 24 hours to 90 days.

The same business can need a different device, or none on the list, a few miles away.

A coffee shop leases a strip mall suite in Mesa. The restaurant use and the shared service both call for an RPA, so the question is whether the landlord's assembly already protects the service or the tenant adds one.

The same concept opens in Gilbert. Restaurants aren't on the town's list, so the town's backflow specialist decides after looking at the site. The county's carbonator rule still applies inside: a reduced pressure or other testable device between the water line and the soda carbonator.

A Chandler owner misses the test date. The three notices went unanswered. With no passing report by the compliance date, the water goes off the next working day and stays off until a passing test is in.

Start with the water provider, then match your business to its list.

1. 1Find the water provider on your water bill. The rules follow the utility, not the mailing city.
2. 2Check your use against that city's list in the table above, then your equipment: carbonators, ice makers, dishwashers, boilers, booster pumps.
3. 3Get the assembly on the permit. In Phoenix, pull the backflow permit from Planning and Development. In Chandler, the assembly has to be on the building plans before the permit issues. County plan review checks carbonator and RO protection separately.
4. 4Hire a tester the city recognizes. Mesa, Glendale and Gilbert give out their lists on request.
5. 5Send the report where the table says, inside the city's window: 7 days in Mesa and Scottsdale, 48 hours after a new Surprise meter, before Chandler's compliance date.
6. 6Calendar the next test from the last passing one, and keep every test and repair record.

Most mistakes assume one statewide list.

• "A double check works anywhere." Chandler allows a DC only where the hazard is "objectionable but not hazardous to health." Restaurants on Phoenix, Mesa, Scottsdale and Glendale lists get an RP or air gap.
• "The building's assembly covers my kitchen." Service protection doesn't replace the fixture protection the plumbing code and the county require on carbonators and RO units.
• "Any tester will do." Mesa and Glendale accept only testers on the city's own list, and Scottsdale can suspend a tester for improper testing.
• "Fire lines follow the same rules." They have their own classes and devices. In Phoenix, fire line tests must be done by a tester the Fire Marshal permits, with results due within 30 days.

Phoenix can shut off water, install the assembly itself and bill the owner, or add a civil penalty of up to 1,000 percent of water charges per billing period (City Code 37-146). Mesa charges a backflow compliance late fee for missing records, and Chandler shuts water off the day after the deadline.

HQ tests, certifies and repairs backflow assemblies on commercial domestic water services and irrigation lines across the Valley, with free estimates. HQ also repairs underground fire lines; testing a fire line's backflow assembly goes to a fire-licensed tester. Call 24/7 if a failed test leaves you facing a shutoff date.