Which backflow assembly types does Scottsdale recognize, and how does it rate hazards?

When protection is required (49-59). Backflow prevention is required at every customer supply line when Water Resources decides the potable water could be contaminated, polluted or degraded by conditions in the user's water system. The protection must be enough for the degree of hazard.

How the city rates a hazard (49-60). Four factors decide it:

• Health: a condition, device or practice that in the division's judgment may threaten contamination or endanger consumers' health.
• Plumbing: a cross-connection in the user's system that no approved assembly protects. It can be a pollution or a contamination hazard.
• Nonhealth: a condition that may pollute the supply in a way that is a nuisance or aesthetically objectionable, but not toxic and not a health hazard.
• System: a condition that may seriously damage the physical parts of the water system or affect water quality over a long time.

Recognized assemblies (49-61). Every device must be lead free under 40 CFR 143, Subpart B and Safe Drinking Water Act Sec. 1417. The four recognized types:

• Air gap: an open vertical distance between the supply outlet and the flood level rim of the fixture or tank. It must be at least twice the supply pipe diameter and never less than 1 inch.
• Reduced pressure principle assembly (RP): two independent check valves with a pressure-differential relief valve between them, test cocks and shutoff valves at each end.
• Double check valve assembly (DC): two independent check valves with test cocks and shutoff valves at each end.
• Pressure vacuum breaker assembly (PVB): a loaded check valve and a loaded air inlet valve on the discharge side, with test cocks and shutoff valves.

Subsection (b) allows an assembly that has received approval from the USC Foundation for Cross-Connection Control and Hydraulic Research, the American Society of Sanitary Engineering or another testing agency the division approves, and that the division approves for use. Approved assemblies must have a local manufacturer's parts and service center.

• Cross-connection: any link between drinking water piping and a source of possible contamination. The hazard rating is about what could come through the link.
• Back-siphonage versus backpressure: back-siphonage is a vacuum pulling water backward. Backpressure is a pump or pressure in the customer system pushing it backward. Section 49-16 defines both terms: backsiphonage follows reduced pressure in the potable system; backpressure occurs when the user’s system pressure exceeds the potable supply pressure. The rankings in 49-62(b) reflect protection strength.
• Test cocks: small valves on the assembly that a tester uses to check that the check valves seal.

Every Scottsdale water customer whose service the city has designated for protection, including owners who install an assembly on a fountain, a house pump, irrigation or a process line. It also covers contractors and designers, who cannot use a device just because it is on a supplier's shelf.

A dental office and a lab in one building. The city rates the medical use as a health hazard and requires an RP at the service. The owner cannot swap in a double check because it costs less.

A contractor with a device that lacks a local service center. The device may be approved by a listing body but still fails because no local parts and service center exists. Confirm that before you buy.

The edge case: a use not on the list. Sec. 49-59(a) lets the division require protection where it decides a hazard exists, even for a use not named in 49-62. The hazard factors in 49-60 guide that decision, and the city decides.

1. 1Check the premises list page for your use and the assembly it calls for.
2. 2Ask the manufacturer for the USC Foundation or ASSE listing and the local parts and service center address before you buy.
3. 3Confirm the assembly is marked lead free.
4. 4Have the assembly sized at least as large as the service connection, and go through the permit steps.
5. 5Plan the yearly test with a certified tester from the start.

• "An approved device works anywhere." The device type must match the hazard the city assigns.
• "An RP and a double check are basically the same." An RP has a relief valve and protects against higher hazards. The code ranks it above the double check.
• "Air gaps are old fashioned." The code lists an air gap as the most restrictive protection, and it must meet the size rule.

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