Gas Fitter Practice Test

Where should a backflow preventer be located in a boiler system?

1. Over flow line connected to the drain

2. Return line close to the boiler

3. 3/4 inch line connecting the boiler and cushion tank

4. Make up water line to the system

The correct answer is: Make up water line to the system

The correct choice is to install a backflow preventer on the make-up water line to the system. This is crucial because the make-up water line is the point of entry for fresh water into the boiler system. It is necessary to prevent any potential contamination from the boiler's water supply from flowing back into the municipal water supply or other potable water sources. In a boiler system, the water is often treated with chemicals to prevent corrosion and scale, which could pose risks if they were inadvertently released back into the clean water supply. By locating the backflow preventer on the make-up water line, you ensure that if a drop in pressure occurs in the boiler system, the backflow preventer will prevent any contaminated water from flowing back into the source, thus maintaining water quality and safety standards. Other locations, such as the overflow line, return line, or a 3/4 inch line connecting the boiler to the cushion tank, do not serve the primary purpose of protecting the potable water supply and hence are not suitable choices for the placement of a backflow preventer.