With an RPZ at the meter, do I need backflow devices inside?

Phoenix's technical guideline on assembly location states the split directly: "The intent of City Code Chapter 37 is to provide SECONDARY backflow prevention for the City water system in addition to the PRIMARY protection required by the Phoenix (Uniform) Plumbing Code."

So in Phoenix's terms:

• Secondary (containment) is the assembly the water department requires at the service, usually right after the meter. The state rule behind it, A.A.C. R18-4-215, says required assemblies "shall be installed as close as practicable to the service connection." Its job is protecting the public system.
• Primary (internal or point-of-use) is what the plumbing code requires at fixtures and equipment. The 2024 IPC opens its backflow section by requiring a water system built "in such a manner so as to prevent contamination from nonpotable liquids, solids or gases being introduced into the potable water supply through cross connections." Its job is protecting the building's own drinking water.

Mesa's code makes the same split. Its purpose section says service connections of listed types "must have backflow protection installed and maintained," and "In addition, certain uses within the customer water system must have point of use protection as required by Section 8-1-9" (City Code 8-1-2). Section 8-1-3 adds: "In addition to service protection, the Department may require point of use protection within a customer water system, based on the degree of hazard at the point of use."

Point-of-use requirements follow the equipment, whatever sits at the meter. Common commercial examples:

• Soda carbonators, coffee brewers and other beverage machines.
• Chemical and soap dispensers at janitor sinks and dish areas (see chemical dispenser backflow rules).
• Commercial dishwashers and anything else with a submerged inlet.
• Dental chairs, autoclaves, sterilizers and lab equipment in medical and research spaces (see lab and science room backflow protection).
• Hose connections on mop sinks, hose bibs and service sinks.

Mesa publishes a full table of point-of-use devices by equipment type in City Code 8-1-9. The IPC sets the general rule in Section 608.3: equipment for "sterilization, distillation, processing, cooling, or storage of ice or foods" that connects to the water supply "shall be provided with protection against backflow and contamination of the water supply system."

A testable device is tested whether it sits at the meter or under a counter. Phoenix's tester guideline, TRT 00636, says its requirements "include internal or PRIMARY backflow preventers required by the Plumbing Code, and containment or SECONDARY backflow preventers required by City Code Chapter 37." The guideline's testing table calls for tests at installation, at repair, alteration or relocation, and at least annually.

Mesa says the same about point-of-use assemblies: "The customer must have the backflow prevention assembly tested annually and ensure that reports are submitted to the Department" (City Code 8-1-9).

Some small devices can't be field tested at all. Maricopa County's food plan review guide says the ASSE 1022 devices common on beverage lines "are not testable" and, where one is the only protection, "a written maintenance policy must be in place that requires the annual inspection of these devices."

Sometimes, in Phoenix, with approval. City Code 37-144 says the protection must be close to the point of service delivery "except that the customer may request that the approved backflow prevention method be located internally within the activity or facility." The catch: "The customer must demonstrate that the proposed location will adequately protect the public water supply." The TRT 00636 table includes a category for internal assemblies "Accepted by P&D to Satisfy P.C.C. 37 Requirements."

That's a case-by-case approval, not a default. Phoenix's location guideline lists its basic criteria, including "Adequate protection MUST be located ahead of every potential cross-connection." In a building where new equipment gets added over time, one assembly at the meter is usually the simpler way to meet that.

Mesa leans the other way for multi-use buildings. Where two or more listed uses share one service connection, "the customer shall install a Reduced Pressure Principle Backflow Prevention Assembly (RPA)" (City Code 8-1-8).

1. 1Walk the building and list every piece of equipment with a water connection.
2. 2Match each one to its required device, using the plumbing code and your city's point-of-use list.
3. 3Find every testable assembly, including the ones inside, and put them all on the yearly test schedule.
4. 4Re-check when equipment changes. A new soda vendor, a new dispenser or a dental chair needs its own protection, even with an RPZ out front.

HQ tests, repairs and replaces domestic backflow assemblies, at the meter and inside, for Valley commercial buildings. Free estimates and upfront pricing.

For a survey of every connection, read cross-connection survey vs backflow test. Kitchen equipment is covered in backflow for soda, ice and coffee machines, and the basics of the term are in what is a cross-connection.