Which backflow device does a Chandler business need?

Subsection (D) opens with "The type of protective device required shall depend upon the degree of hazard which exists." The first rule is the one quoted above: where a premises has an auxiliary water supply and no other rule below applies, the city system is protected by an approved air gap or an approved reduced pressure principle device. The other five rules:

• Objectionable, not hazardous (D2): water or a substance that would be objectionable but not hazardous to health, if it got into the public system, needs an approved double check valve assembly.
• Dangerous to health (D3): any material dangerous to health that is handled in a way that creates an actual or potential hazard needs an air gap or RP device. The code's examples are chemical manufacturing plants, hospitals, mortuaries, plating plants, sewage treatment plants and sewage pumping stations.
• Uncontrolled cross-connections (D4): actual or potential ones need an air gap or RP device at the service connection.
• Cannot be surveyed (D5): where security or other restrictions make a complete in-plant survey impossible or impracticable, the code requires maximum protection, an air gap or RP device on each service.
• Tankers and spray tanks (D6): an air gap or RP device.

Subsection (C) is the trigger. A device goes on each service line before the first branch line when the premises has an auxiliary supply that may not be safe, handles industrial fluids or another objectionable substance in a way that creates an actual or potential hazard, or has internal cross-connections that cannot be permanently corrected and controlled, or plumbing too intricate to inspect.

Chandler defines most of them in 52-1, so you do not have to guess.

• Air gap: an unobstructed vertical distance through free air. The approved gap is at least double the diameter of the supply pipe, measured above the vessel's overflow rim, and never less than one inch.
• Reduced pressure principle (RP) device: two check valves with a differential relief valve between them, shutoff valves on each side and test cocks.
• Double check valve assembly: two check valves with a shutoff valve at each end. Chandler also defines a double check-detector check assembly, and says it protects only against a nonhealth hazard.
• Atmospheric vacuum breaker: protects against a health hazard under back-siphonage only.
• Auxiliary water supply: any supply on the premises other than the city's approved potable supply, such as a well, spring, treated effluent or "industrial fluids."
• "Objectionable but not hazardous": the code does not define the phrase beyond 52-1's "pollutant" hazard, a nuisance or aesthetically objectionable condition that is not dangerous to health. Treat any example you hear as a reading, not the code.

Section 52-36 speaks of premises, not of commercial buildings. Chandler 52-1 defines residential as single-family homes, duplexes and triplexes. The rule does not apply the same way to an older device that was approved when installed and has been properly maintained. Subsection (I) lets it stay, except for the inspection and maintenance requirements, so long as the Director is assured it will protect the utility system. If the device is moved, needs more than minimum maintenance or the Director finds the maintenance a health hazard, it must be replaced with one that meets the section.

A plating shop in a new industrial unit. Plating plants are named in (D)(3). The plans show an air gap or RP device, and the model and size have to be approved by the Director.

A tenant with an objectionable-but-harmless process. If the Director finds a substance that would spoil the water without endangering health, (D)(2) calls for the double check assembly, not the RP. The code leaves it to the city to decide which side of that line a process falls on.

A plant that cannot go dry. A facility that needs water around the clock cannot shut down for the annual test. Subsection (E) requires two sets of assemblies in parallel there, and each must be at least the cross-sectional area of the service or meter.

The edge case: the grandfathered device. A building has a device installed under an older standard. It stays under (I) until it is moved or needs more than minimum maintenance, and then it comes out. Glendale's 33-97(b) works the other way and requires non-complying devices to be replaced.

1. 1Ask for the city's approved assemblies list. Section 52-36(F) says it is made available on written request to the department, and 52-36(J) says the city furnishes the list to any customer required to install an assembly.
2. 2Choose the device by the hazard rule above and size it to at least the water service or meter.
3. 3Show the assembly on the plans (see our page on 52-36(H) backflow assemblies on building plans). Questions go to the Plan Reviewer of the Day at 480-782-3078.
4. 4After it is installed, book the annual test with a tester from the city's list and send the passing report to Chandler Backflow Reports, 480-782-3665.

• Myth: Chandler has a list of businesses like Scottsdale. It does not. Scottsdale's 49-62(a) lists activities and the assembly for each. Chandler decides by hazard and names only examples.
• Myth: Every device in a commercial building is an RP. A double check valve assembly is the rule for an objectionable, non-health substance.
• Myth: Any gap counts as an air gap. Chandler's 52-1 sets the measure at double the supply pipe diameter, and never under one inch.
• Myth: Fire line devices follow the same approval. They also need UL-FM approval under 52-36(F).

This page explains the code. The adopted text on Municode governs.