If a single check valve is installed in a water system, a thermal expansion tank is needed.

If a single check valve is installed in a water system, a thermal expansion tank is needed.

• A. Air Chamber
• B. Thermal Expansion Tank
• C. Backflow Preventer
• D. Pressure Reducing Valve

Answer: (B)

When a check valve is installed, the water system becomes a closed loop. As water is heated, it expands, and with no path to flow back to the supply, the expanding water raises the system pressure. A thermal expansion tank provides a dedicated, air-filled space that absorbs this extra volume: as the water expands, it compresses the air in the tank, keeping pressure from spiking and protecting components. An air chamber can offer a similar idea, but air tends to dissolve into water or leak away over time, making it less reliable in the long run. A backflow preventer stops reverse flow but doesn’t accommodate expansion. A pressure reducing valve lowers pressure but doesn’t provide a place for the expansion to go. So the thermal expansion tank is the appropriate choice.

When a check valve is installed, the water system becomes a closed loop. As water is heated, it expands, and with no path to flow back to the supply, the expanding water raises the system pressure. A thermal expansion tank provides a dedicated, air-filled space that absorbs this extra volume: as the water expands, it compresses the air in the tank, keeping pressure from spiking and protecting components. An air chamber can offer a similar idea, but air tends to dissolve into water or leak away over time, making it less reliable in the long run. A backflow preventer stops reverse flow but doesn’t accommodate expansion. A pressure reducing valve lowers pressure but doesn’t provide a place for the expansion to go. So the thermal expansion tank is the appropriate choice.