Restaurant Carbonator, Boiler, and Fire Line Backflow Protection
A 1,800-square-foot restaurant in Koreatown has a 1-1/2-inch domestic water service, a 4-inch dedicated fire sprinkler line, and a 3/4-inch landscape irrigation line. The existing domestic service has only a single check valve at the meter. The tenant is adding a carbonator for soda, a chemical dispenser for the dish machine, and a new hot-water boiler. The carbonator will be connected with a 3/8-inch copper line and a screwdriver-type shutoff; there is no air gap. The boiler has a fill valve with a bypass. The irrigation has pop-up heads and a hose bibb at the loading dock. The fire sprinkler system is wet and has no antifreeze. The plan reviewer asks for a containment and isolation strategy, device selection, and annual testing requirements.
1. Identify the cross-connection hazards and the type of backflow protection required for each connection.
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The carbonator is a high hazard because carbon dioxide can be forced into the potable line; an air gap is preferred, and if an air gap is not feasible, an RPZ is required. The chemical dispenser is a high hazard and needs an air gap or RPZ. The boiler fill connection is a high hazard because of boiler water and chemicals; use an air gap or RPZ, and do not rely on the bypass. The irrigation system is a low-to-moderate hazard if there are no chemicals; a pressure vacuum breaker or RPZ is typically required, and an RPZ is required if chemical injection is present or the heads are below grade. The wet fire sprinkler system without antifreeze is normally protected by a double check detector assembly; if antifreeze or chemical additives are added, an RPZ is required. The existing single check at the meter is not adequate containment.
2. Where should containment and isolation assemblies be located, and what accessories are required?
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Containment should be on the domestic service immediately downstream of the meter and upstream of all branch takeoffs, so the entire premises is protected. For this occupancy, a testable RPZ is the likely containment device. Isolation devices are then installed at each hazard: air gap or RPZ for the carbonator, air gap or RPZ for the chemical dispenser and boiler, PVB or RPZ for irrigation, and a double check detector assembly for the fire line. Each assembly must be accessible for testing and repair, protected from freezing, provided with test cocks and shutoff valves, and installed without a bypass except an approved test bypass. Because an RPZ creates a closed system, add thermal expansion control at the water heater. The fire line assembly must be listed for fire protection and installed with the required drain and clearance.
3. What are the testing and maintenance obligations, and what should happen if an assembly fails a test?
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In Los Angeles, backflow assemblies must be tested at installation and annually by a certified backflow tester, with results filed with LADBS. The device must be registered and tagged. Testers check check-valve tightness and relief-valve operation. If a check valve fails or the relief valve dumps, the assembly has failed. The water should be shut down or isolated, the device repaired or replaced with an approved assembly, and the assembly retested. A failed device cannot remain in service with a note. Do not remove or bypass the device to keep the restaurant open. The owner should be given the test report and the next test due date.