Why is it important to have check valves in the connections of high-pressure boilers?

Check valves are essential in high-pressure boiler systems primarily to prevent backflow. When water or steam flows through pipes under high pressure, any reverse flow can lead to significant safety issues, including the potential for water hammer, system contamination, or equipment damage. By installing check valves, which only allow flow in one direction, the system ensures that the fluid remains under control and prevents reverse currents that could disrupt the operational integrity of the boiler.

In terms of the other options, while regulating temperature, maintaining water level, and reducing maintenance costs may be important considerations in the overall operation of a boiler system, they do not directly pertain to the primary function of check valves. Regulation of temperature and water level is managed through different components such as thermostats and level sensors. Reducing maintenance costs is a broader outcome that can result from the effective operation of a system with check valves but is not their specific function. Therefore, the critical role of check valves in preserving proper directional flow is paramount, underscoring why preventing backflow is the correct answer.