Mesa City Code 8-1-10: backflow rules for fire sprinkler systems

Sprinkler systems must have backflow protection under 8-1-8 and these three rules.

DCVA. Allowed when the system is connected to the domestic water system only. No connections to auxiliary or supplementary water, no fire suppressing chemical additives, drains discharging to atmosphere through an air gap, and piping that meets National Fire Protection Association requirements.

RPA. Required where "any form of chemical additive is used such as antifreeze, corrosion inhibitors, and foaming agents," where the system connects to an auxiliary water source, and for private fire lines with hydrants.

Combined service. A service that provides both fire and domestic water to a property with a combined system needs an RPA, and point-of-use protection could be required on each connection.

The plumbing code adds its own line. Mesa's amended IPC 608.17.4 says the potable water supply to sprinkler and standpipe systems "shall be protected against backflow, in accordance with Mesa Standard Details." Two exceptions: no isolation is required for systems in the distribution system with no fire department connection, or for deluge, preaction or dry pipe systems.

• DCVA. Double check valve assembly. Two check valves in series, for low hazard connections.
• RPA. Reduced pressure principle assembly. Adds a relief valve, for high hazard connections.
• Auxiliary water source. A supply other than the city's, such as a well, tank or pond.
• Modified in any way. Not defined. Read plainly, it reaches any change to the sprinkler system itself. Adding heads or re-piping would count.

Owners and contractors on any Mesa property with a sprinkler system on city water. It does not force an immediate retrofit on an existing system: 8-1-10(B) exempts it "unless or until" a trigger occurs.

A warehouse adds high racks. Sprinkler density has to go up, which is a trigger. The owner upgrades an old check valve to a DCVA as part of that work.

A tenant re-pipes heads. Any modification counts. The system moves out of its exemption and gets a DCVA.

The edge case. A cold storage building fills its system with antifreeze. The upgrade is not a DCVA but an RPA, because an additive alone makes it a health hazard.

1. 1Identify which situation you are in: city water only, additive, auxiliary supply, hydrants or combined service.
2. 2For an existing system, check whether any 8-1-10(B) trigger applies before assuming it's exempt.
3. 3Have the sprinkler contractor design the assembly to Mesa Standard Details. Ask Backflow Prevention for the current detail: 480-644-6462 or backflow@mesaaz.gov.
4. 4Show the assembly on plans and get it reviewed before installation, then pull the permit through Development Services.
5. 5After installation, use a tester from Mesa's fire contractor list and keep the annual test on the calendar.

• "Old systems are grandfathered forever." Only until a trigger, and a modification of any kind is one.
• "A DCVA works everywhere." Additives or an auxiliary supply require an RPA.
• "The plumbing code alone decides." The utility code in Title 8 sets the assembly type, and the IPC amendment points to Mesa's own details.
• "Any detector assembly is accepted." Mesa's IPC amendment strikes the double check detector and reduced pressure detector rows from Table 608.1. Ask which assembly types the Mesa Standard Details accept before ordering one.