What is a possible consequence of a malfunctioning pressure relief valve?

A malfunctioning pressure relief valve can indeed lead to potential flooding from excess water pressure. The pressure relief valve is designed to maintain safe pressure levels within a system, such as a boiler or water heater that can be part of a heating system. When this valve fails or does not open at the set pressure, it can allow excessive pressure to build up. In a water heating system, for instance, this increased pressure can lead to water being forced out of the system, potentially causing leaks and flooding.

In contrast, while other options may seem beneficial or desirable, they do not accurately reflect the consequences of a malfunctioning pressure relief valve. Improved efficiency of the heating system and lower energy bills would not occur as a result of such a malfunction. The furnace may not operate continuously in a safe manner either; instead, it may shut down or operate inefficiently due to the problems created by excess pressure. Thus, the most relevant and accurate consequence of a malfunctioning pressure relief valve is indeed the risk of flooding caused by excess water pressure.