When does a Scottsdale fire sprinkler system need a double check assembly?

Subsection (a) applies to a customer connection that supplies water only to a fire sprinkler system. The assembly goes in following the city's standard details. A double check valve assembly is required when any of these occurs:

1. 1During new construction on commercial buildings.
2. 2An existing Class 1 or 2 sprinkler system is modified from its present condition in a way that requires new hydraulic calculations.
3. 3An existing single check valve shows deterioration or defects, or the owner lacks the inspection records subsection (c) requires.
4. 4The existing system or its condition is a hazard to public health, safety or welfare.

The rest of the section adds five duties:

• Continuous supply (b): if the fire chief or designee decides the sprinkler supply cannot be interrupted during testing, the user installs two assemblies in parallel at the service connection, each as large as the service connection.
• Annual inspection of single checks (c): owners of existing Class 1 and 2 systems with no double check must have the internal parts of the single check inspected and maintained every year, following NFPA 25 or division guidelines. A defective single check is reported within 24 hours to the fire department and Water Resources. Section 49-64(c) says to obtain a permit and complete double-check replacement within 45 days. Section 49-65(f), however, calls for immediate replacement after a malfunction or abnormality. Report the defect promptly and follow Water Resources and the fire department's direction; do not treat 45 days as permission to leave defective fire protection in service.
• Flow test before installing (d): before an assembly goes onto an existing sprinkler system, the system must be tested to confirm it still meets NFPA 13 minimum flow with the assembly added. The fire department approves the plans and hydraulic calculations first, and the approved plans must be on site for the fire department's underground inspection and flow test.
• Penalty (e): a civil fine up to $1,000, with each day counted as a separate offense.
• Repeat offense (f): a second or later violation within two years is a misdemeanor.

Section 49-62(a)(24) sets the assembly by AWWA M14 class: Class 1 and 2, and Class 3, get a double check; Classes 4, 5 and 6 get an RP.

• Class 1 or 2 system: an AWWA M14 classification for the least hazardous sprinkler systems, those fed from the city supply without added chemicals or outside water sources. The code refers to the manual and does not define the classes itself.
• Single check valve: an older one-way valve with no test cocks. The code treats it as acceptable only with annual internal inspection.
• Hydraulic calculations: the engineering that shows the system delivers enough flow and pressure. Adding an assembly costs pressure, so the calculations must be redone.

Owners of commercial buildings with sprinkler systems fed by a sprinkler-only connection, plus the fire sprinkler contractor and fire department involved. Backflow-assembly certification and city filing are part of HQ's service. Sprinkler-system design, hydraulic calculations, flow testing and fire-code certification are separate contractor work.

A new office building. The double check is part of the sprinkler service from the start. The fire department reviews the plans and calculations, and the assembly appears on the plan sheets the city approves.

A warehouse that adds racking. The sprinkler system is reworked for denser storage and needs new hydraulic calculations, so the old single check must be replaced with a double check.

The edge case: the flow test fails. Subsection (d) says a system must still meet NFPA 13 minimum flow with the assembly in place. If it does not, the system needs design work before an assembly can go in, which is a fire sprinkler contractor's job.

1. 1Find out what is at your sprinkler service today: a double check, an RP or an old single check.
2. 2If you have a single check, confirm your annual inspection records exist. Missing records are a trigger under (a)(3).
3. 3Hire a licensed fire sprinkler contractor for the flow test, hydraulic calculations and fire department submittal.
4. 4Have a certified backflow contractor set the assembly under its own permit, using the installation permit page.
5. 5Send each year's inspection records to both the fire department and Water Resources, as Sec. 49-65(f) requires. Use the city's Commercial Services page for the current Water Quality contact.

• "A single check is fine forever." Annual internal inspection is required. A defect triggers prompt reporting; 49-65(f) calls for immediate replacement even though 49-64(c) also lists a 45-day completion period.
• "A backflow test replaces the sprinkler flow test." These are different tests. Sprinkler hydraulic calculations and flow-test approval must be handled with the qualified sprinkler contractor and fire department.
• "Water service to sprinklers can be shut off like any other line." Sec. 49-66(c) exempts a sprinkler-only line from disconnection, but the fines in 49-64(e) still apply.

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