Question 27

A portable water supply can be protected from backflow using a reduced pressure backflow preventer.

A reduced pressure backflow preventer is specifically designed to prevent backflow in water supply systems by maintaining a pressure differential, making it the most effective choice in this context.

A) Reduced pressure backflow preventor

This option is correct because a reduced pressure backflow preventer effectively protects against backflow by utilizing two check valves and a pressure differential chamber, ensuring that contaminated water cannot flow back into the potable water supply.

B) Atmosphere-type vacuum breaker

An atmosphere-type vacuum breaker is not suitable for this application because it is designed to prevent back siphonage only and may not provide adequate protection against backpressure situations, which can occur in fire protection systems.

C) Pressure-type vacuum breaker

While a pressure-type vacuum breaker can be used to prevent backflow, it is less reliable than a reduced pressure backflow preventer in scenarios where the system might experience backpressure, making it an inadequate choice for protecting a portable water supply connected to an automatic fire sprinkler.

D) Air gap

An air gap is a physical separation between the water supply and potential contaminants, which prevents backflow. However, it is not feasible for all applications, particularly in systems that require a continuous water supply like fire sprinklers, making it less suitable in this context.

Conclusion

The reduced pressure backflow preventer is the most reliable method for preventing backflow in a portable water supply system connected to an automatic fire sprinkler, as it effectively handles both backpressure and back siphonage. Other options, while they have specific uses, do not provide the same level of protection and are therefore inferior in this scenario.