Which Phoenix businesses need a backflow preventer, and which type?

The subsection opens with the rule: "An approved backflow prevention method is required for the activities or facilities listed in this subsection that are connected to the public water system." The list is grouped, and each entry names the allowed methods:

• Commercial and educational: restaurants, supermarkets and butcher shops (air gap or RP); car washes (air gap or RP); retail and wholesale nurseries and equestrian properties (air gap or RP); schools and colleges with laboratories (air gap or RP); multi-story buildings with booster pumps or above-ground storage tanks (air gap, RP or double check); interconnected multiple services (air gap, RP or double check); mobile home and RV parks (RP or double check).
• Shopping centers and shells: retail shopping centers, strip malls, and retail or industrial shell buildings "when one service supplies more than one tenant" (RP only).
• Medical: hospitals, medical buildings, clinics, morgues, mortuaries, nursing homes, research laboratories, veterinary and animal grooming shops (air gap or RP).
• Industrial: plating, chemical, laundry, food processing, breweries, semiconductor plants and similar (air gap or RP, with a double check allowed for a few, such as bottling, dairies and metal fabrication).
• Portable and temporary: construction water services and mobile equipment such as water trucks and street sweepers (air gap or RP).
• Fire systems: Class 1 or 2 need a backflow prevention assembly, with no type named. Class 3, 4, 5 or 6 need an RP.
• Irrigation: a system with chemical injection needs an RP. One with elevated areas higher than six inches below the vacuum breaker, or with multiple services, needs an RP. One not subject to backpressure can use a pressure vacuum breaker. Solar heating (direct and auxiliary) needs an RP.

Anything not listed is decided by the director "on a case-by-case basis."

• Air gap: a physical open space between the supply pipe and the receiving tank, at least double the pipe diameter and never less than one inch.
• RP (reduced pressure principle assembly): two check valves with a relief valve between them. It is the strongest of the mechanical assemblies.
• Double check (DC): two independently acting check valves, allowed only where the hazard is lower.
• PVB (pressure vacuum breaker): protects against backsiphonage on irrigation and must sit above ground.
• Point of service delivery: the customer's side of the water meter.

Any customer on Phoenix city water with a listed use. The code says the requirements "do not apply to single-family residences used solely for residential purposes" unless a cross connection problem is specifically identified. Duplexes, apartments, offices and every other property type are not covered by that exemption.

• A restaurant opens in a former retail space. Restaurants are on the list, so the tenant improvement plans need an air gap or RP at the service. Under 37-143 the Planning and Development director requires the right backflow protection as a condition of issuing the building permit, and the assembly is tested every year afterward.
• A landlord splits a shell building into three tenants on one meter. The shell building rule applies the moment one service feeds more than one tenant, and it names only the RP.
• A single-family home adds a dedicated irrigation line with fertilizer injection. Homes are exempt unless the city identifies a cross connection problem, and that call is the city's. If it does, the irrigation entry in the list applies, and it names an RP for systems using chemical injection.
• A contractor fills a water truck at a hydrant. Mobile equipment using public potable water is on the list. The truck needs an air gap or RP.

1. 1Find your use in the list above and note the allowed assemblies.
2. 2Check whether the property already has an assembly near the meter. If it does, look up its last test date.
3. 3Have a licensed plumber pull the Planning and Development plumbing permit for the assembly and place it as close as practicable to the meter.
4. 4Schedule the city inspection ($195 for the first device, $98 for each additional).
5. 5Hire a certified tester for the first test and every annual test afterward. See the customer duties page for what has to be filed.

• "The plumbing code inside my building already covers this." The city code adds secondary protection at the service, on top of the plumbing code's primary protection.
• "A double check is cheaper, so I will use it." For restaurants, supermarkets, car washes and shopping centers, the code allows only an air gap or an RP.
• "My tenant space is small, so it does not count." For strip malls and shells the trigger is one service feeding more than one tenant, not size.
• "Single-family means no rules." The exemption ends where a cross connection problem is found.