Boilers must have a combination device to maintain pressure and protect the plumbing system. Which components comprise this combination?

• A. Increase efficiency
• B. Backflow preventer only
• C. Pressure reducing valve only
• D. Pressure reducing valve and back flow preventer

Answer: (D)

The main idea is that a boiler needs both pressure control and protection against backflow to keep the system safe and reliable. A combination device does exactly that by pairing a pressure reducing valve with a backflow preventer. The pressure reducing valve lowers the incoming water pressure to a safe, stable level for the boiler and piping, preventing over-pressurization. The backflow preventer stops water from flowing backward into the supply when pressures change or cross-connections exist, protecting potable water from contamination. Together, these two functions in one assembly ensure proper feed pressure and system protection. The other options don’t provide both functions: backflow prevention alone lacks pressure reduction, and pressure reduction alone lacks backflow protection, while a choice about increasing efficiency isn’t about protective and regulatory components.