ServSafe emphasizes air gaps and backflow preventers like reduced pressure zone assemblies or double check valve assemblies. These devices create a physical break or use internal check valves to prevent contaminated water from flowing back into the potable water supply due to changes in pressure.
Backflow can be prevented by several methods, with air gaps being one of the most reliable. An air gap is a physical separation between the water supply and a contaminated source. Other methods include using backflow prevention devices like reduced pressure zone (RPZ) assemblies, double check valves, or pressure vacuum breakers. Regular testing and maintenance of these devices are crucial to ensure their effectiveness and compliance with health codes.
An air gap prevents backflow by creating a physical, vertical separation between the water outlet and the flood level rim of the receiving fixture. This open space makes it impossible for contaminated water to be siphoned back into the potable water supply, even under conditions of negative pressure. It's considered the most dependable method because it has no mechanical parts to fail.
A reduced pressure zone (RPZ) assembly is a mechanical backflow prevention device designed to protect against both backpressure and backsiphonage. It consists of two independently operating check valves, an automatically operating differential relief valve located between the two check valves, and two shut-off valves. This design creates a low-pressure zone, which is vented to the atmosphere if either check valve leaks, preventing contamination.
A double check valve assembly (DCVA) is used to protect against backpressure and backsiphonage in situations where the potential hazard is considered non-health threatening. It consists of two independently operating check valves, each with a tightly closing shut-off valve on either side, and test cocks for field testing. It's suitable for protecting against pollutants, but not against highly toxic or hazardous contaminants.
No, a pressure vacuum breaker (PVB) is designed to protect against backsiphonage only, not backpressure. It consists of a spring-loaded check valve and an independently operating, spring-loaded air inlet valve. When the water pressure drops, the air inlet valve opens, breaking the vacuum and preventing contaminated water from being siphoned back. It must be installed at least 12 inches above the highest point of the downstream piping.
Regular testing of backflow prevention devices is crucial to ensure they are functioning correctly and providing the intended protection. Mechanical devices can wear out, fail, or become fouled over time, compromising their effectiveness. Annual testing by a certified backflow prevention device tester is typically required by regulatory authorities to maintain compliance and safeguard public health from potential water contamination.
Backpressure occurs when the downstream pressure becomes greater than the supply pressure, forcing contaminated water into the potable water system. This can happen due to pumps, thermal expansion, or elevation differences. Backsiphonage, on the other hand, is caused by a negative or sub-atmospheric pressure in the potable water supply, which draws contaminated water into the system, often due to a sudden drop in supply pressure.
ServSafe emphasizes the importance of backflow prevention in food establishments to protect against cross-contamination of potable water. They advocate for the proper installation and maintenance of backflow prevention devices, such as air gaps, RPZ assemblies, and double check valves, depending on the hazard level. Training covers identifying potential cross-connection points and understanding the regulatory requirements for water system safety.
Common sources of backflow in a restaurant kitchen include submerged hoses in mop sinks, dishwashers, or prep sinks, which can create a cross-connection if the water pressure drops. Carbonated beverage dispensers are another high-risk area, as the CO2 gas can create backpressure. Ice machines, steam tables, and garbage disposals also pose potential backflow risks if not properly protected with air gaps or approved backflow prevention devices.
Visual indicators of a backflow incident can include discolored water, unusual odors, or a noticeable change in water taste from a tap that was previously connected to a potential contaminant source. While these are signs that backflow may have occurred, many incidents are not visually apparent. This underscores the necessity of proper backflow prevention devices and regular testing to ensure the safety of the water supply.