Where must a backflow preventer be installed at a Phoenix property?

City Code 37-144 says: "A reduced pressure principle assembly or double check valve assembly may not be installed in a basement, meter box, pit, or vault. A pressure vacuum breaker assembly must be installed above ground." All assemblies "must be accessible for testing and maintenance."

The code sets the position: the assembly goes "as close as practicable to the point of service delivery," which the code defines as the nearest point where the assembly can be installed. Where a driveway or sidewalk is in the way, close as practicable means the nearest point after the obstacle, "but in no event beyond the first tap." An air gap follows the same location rule, and all piping between the customer's connection and the receiving tank must be entirely visible unless the Planning and Development director approves otherwise. A customer may ask to place the assembly inside the building, but has to show that the location protects the public supply.

The 2024 plumbing code amendments write the same limits into the building code:

• IPC 608.8.1: "Backflow prevention devices shall not be installed in pits, underground vaults, or submerged locations."
• IPC 608.15.3: "not less than 12 inches between the lowest portion of the assembly and grade, floor, or platform." Elevated installations above 5 feet need a platform that can hold a tester. Secondary assemblies go above ground as close as practicable to the service, with a minimum 3-foot clear space for testing, maintenance and repair.

The city's location guideline (TRT 00634) adds site rules. Assemblies must not sit in traffic visibility triangles or where the zoning ordinance bars utility devices. Placing one behind the front yard setback line or just around a building corner is typically acceptable without special justification if the reason is readily apparent on the plan. The Design Standards Manual puts a backflow preventer on private property outside the right of way or a public utility easement.

• Point of service delivery: the downstream (customer) side of the meter. For an unmetered connection it is the boundary between the public right of way or easement and private property.
• Close as practicable: the nearest workable point to that boundary.
• Secondary assembly: the city-required assembly at the service, as opposed to internal plumbing-code protection.

Anyone placing or relocating a required backflow assembly on a Phoenix property. Designers show the location on plumbing and site plans, and the city checks it before the permit issues. The 12-inch clearance applies to backflow assemblies generally. The above-ground rule and the 3-foot clear space are written for secondary assemblies.

• A new restaurant pad. The civil plans put the RP in a vault at the curb to hide it. The city rules put it above ground, on private property, close to the meter, with a 3-foot clear space around it.
• A landscape screen wall goes up around an existing assembly. The code requires every assembly to be accessible for testing and maintenance, and a wall that boxes in the tester works against that.
• The same owner asks to put the assembly inside the building. The answer flips: the code allows an internal location only if the customer demonstrates that it adequately protects the public water supply.

1. 1Locate the meter and mark the nearest point where an assembly can go without hitting a driveway or sidewalk.
2. 2Put the assembly above ground on private property, with 12 inches under it and a 3-foot clear space around it.
3. 3Show its size, type and location on the plumbing and site plans, plus the piping to the meter.
4. 4Keep the assembly out of visibility triangles and easements.
5. 5If you must place it inside the building, ask the director for approval and show how the location protects the public supply.

• "A meter box is the standard spot." RP and DC assemblies may not go in a meter box, pit or vault.
• "Close to the meter means right at the sidewalk." The code allows the nearest point after the obstacle, never beyond the first tap.
• "Clearance is a manufacturer suggestion." The 2024 amendment sets 12 inches and a 3-foot clear space for secondary assemblies.