A backflow preventer used in a boiler system should be located in the:

A backflow preventer is a crucial component in ensuring that water does not flow backward into the potable water supply, preventing contamination. In a boiler system, the makeup water line is where water is added to the system to replace any water that has been lost due to evaporation or system leaks.

Installing the backflow preventer in the makeup water line is essential because this is the point at which non-potable water from the boiler could potentially contaminate the potable water supply. If the water were to flow backward through the makeup line, it could introduce contaminants into the drinking water, compromising safety and public health.

By positioning the backflow preventer in the makeup water line, it serves its primary function of protecting the water supply from potential backflow contaminants originating from the boiler system. This placement ensures that any pressure changes or backpressure in the system do not allow boiler water to enter the clean water supply, which is vital for maintaining safe and drinkable water standards.