Two layers. At the service, Phoenix requires an air gap or RP for research labs and for schools and colleges with labs, and Mesa requires an RP for any laboratory. Inside, the plumbing code wants protection at each outlet, such as ASSE 1035 lab faucet vacuum breakers, with lab-area hose vacuum breakers at least 6 feet above the floor.
At the service: Phoenix and Mesa rules
Phoenix's backflow code lists facilities that need protection at the point of service delivery. Under City Code 37-144, the list includes "Research laboratories (air gap or RP)," "Film laboratories (air gap or RP)" and "Schools and colleges with laboratories (air gap or RP)." Hospitals, medical buildings and clinics are on the list too, also with air gap or RP.
Phoenix's 2024 plumbing code amendments add a second layer for some of these uses. Amended IPC Section 608.7.2 says listed facilities "shall have a Secondary Reduced Pressure Principle Backflow Prevention assembly installed as close as practicable to each point of service delivery," and the list includes "Hospitals, surgical clinics, medical buildings, laboratories." Secondary assemblies must also be "installed above ground" with "A minimum 3-foot (914 mm) clear space" for testing (Section 608.15.3).
Mesa goes further on labs. Mesa City Code 8-1-8 requires an RPA at the service for "Laboratories, regardless of whether using toxic or nontoxic materials," and for "Schools, colleges, and universities." So a Mesa school building needs an RP at the service whether or not it has a chemistry room.
Inside the lab: point-of-use protection
The meter assembly protects the city's main. It doesn't protect the drinking fountain in the hallway from the lab sink in the next room. That's what the plumbing code's outlet rules do.
Lab faucets. The 2024 IPC's Table 608.1 lists a "Laboratory faucet backflow preventer" under ASSE 1035, rated for high or low hazard against low head backpressure and backsiphonage. They're typically small vacuum breakers built into, or added to, the serrated hose outlet of a lab faucet.
Hose connections. Section 608.3.1 is specific about height: "Vacuum breakers for hose connections in health care or laboratory areas shall be not less than 6 feet (1829 mm) above the floor." A vacuum breaker mounted low behind a bench doesn't meet it.
Hospital and clinical fixtures. The same section says hospital fixture supplies shall be protected "with a reduced pressure principle backflow prevention assembly, an atmospheric or spill-resistant vacuum breaker assembly, or an air gap."
Open outlets. Where a faucet discharges into a sink without a hose, the air gap between the spout and the flood rim is the protection. Section 608.16.1 sets those gaps by outlet size in Table 608.16.1, and adds that "Openings and outlets equipped for hose connection shall be protected by means other than an air gap."
Mesa's point-of-use table names the acceptable devices: "Lab Equipment" takes an AVB, PVB or RPA, "Aspirators (medical)" take an AVB or PVB, and "Specimen Tanks" take an AVB or PVB (City Code 8-1-9).
Testing and upkeep
The testable assemblies, the RP at the service and any PVB or RP serving lab equipment, get tested every year. Mesa states for point-of-use assemblies that "The customer must have the backflow prevention assembly tested annually and ensure that reports are submitted to the Department" (City Code 8-1-9). Faucet-mounted lab vacuum breakers are devices rather than testable assemblies, so keep them on the maintenance checklist and replace any that leak or stick.
A few problems show up in labs and science rooms:
- Missing faucet vacuum breakers after a faucet is swapped for a cheaper model.
- Hoses left submerged in sinks, tubs or containers overnight.
- Aspirators connected straight to the supply with no device.
- Remodels that add sinks, eyewash units or equipment without anyone checking the backflow plan.
Phoenix's code requires a permit from the Planning and Development Department "for the installation of any backflow prevention assembly or for the modification of any plumbing system" (City Code 37-143). A school or lab remodel is the time to get the whole picture on the plans.
A quick checklist
- 1Confirm the service has the assembly your city's list calls for, and that it's tested yearly.
- 2Check every lab faucet with a serrated hose outlet for a vacuum breaker.
- 3Measure hose-connection vacuum breakers in lab areas: 6 feet above the floor or higher.
- 4List every testable assembly inside, as well as the one out front.
- 5Re-check after any remodel or equipment change.
HQ tests, repairs and replaces domestic backflow assemblies for schools, clinics and commercial buildings across the Valley.
For how the service assembly and the inside devices fit together, read if there's an RPZ at the meter, do I still need devices inside. Dental suites have their own page: does a dental office need a backflow preventer. For safety fixtures in the same rooms, see what plumbing an emergency eyewash needs.