Question 40

A double check-valve assembly is required for the potable water supply to a boiler when there are no conditioning chemicals in the water supply.

A double check-valve assembly is necessary in this scenario to prevent backflow and ensure the safety of the potable water supply, particularly when no conditioning chemicals are present.

A) A backflow preventer with an intermediate atmospheric vent

This option is incorrect because a backflow preventer with an intermediate atmospheric vent is typically used in situations where there is a risk of backsiphonage. However, it is not the required device for a boiler's potable water supply when no conditioning chemicals are involved.

B) A reduced pressure principle backflow preventer

This option is also incorrect. While a reduced pressure principle backflow preventer is effective in protecting against backpressure and backsiphonage, it is not specifically required for the boiler's potable water supply in the absence of conditioning chemicals.

C) A double check-valve assembly

This option is correct as a double check-valve assembly provides adequate protection against backflow in situations where the water supply is not treated with chemicals. It is designed to maintain the integrity of the potable water supply system.

D) A pressure-type vacuum breaker

This option is not suitable in this context. A pressure-type vacuum breaker is primarily used to prevent backsiphonage in horizontal installations and is not the required device for the boiler's potable water supply when there are no conditioning chemicals.

Conclusion

A double check-valve assembly is the appropriate backflow prevention device for a boiler's potable water supply when conditioning chemicals are absent, as it effectively prevents backflow without the need for more complex systems. Other options, while useful in different contexts, do not meet the specific requirements outlined in the question.