If a single check valve is installed in a water system, a ________ ______ ______ is needed.

If a single check valve is installed in a water system, a ________ ______ ______ is needed.

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

Answer: (D)

When a water system has a single check valve, the pipe becomes a closed loop for water. As water is heated, it expands, and with nowhere to go, the expansion raises the system pressure. That pressure rise can stress the valve and piping or even force water back through the heater. A thermal expansion tank provides a dedicated space for the expanded water and uses a compressible air cushion to absorb the pressure increase, keeping the system pressure within safe limits and protecting components. The other options don’t address this expansion issue: an air gap prevents cross-connection at fixtures but doesn’t handle expansion; a backflow preventer is a higher-level backflow device not specifically for expansion; a pressure reducing valve lowers incoming pressure but doesn’t accommodate the extra volume from thermal expansion.

When a water system has a single check valve, the pipe becomes a closed loop for water. As water is heated, it expands, and with nowhere to go, the expansion raises the system pressure. That pressure rise can stress the valve and piping or even force water back through the heater. A thermal expansion tank provides a dedicated space for the expanded water and uses a compressible air cushion to absorb the pressure increase, keeping the system pressure within safe limits and protecting components. The other options don’t address this expansion issue: an air gap prevents cross-connection at fixtures but doesn’t handle expansion; a backflow preventer is a higher-level backflow device not specifically for expansion; a pressure reducing valve lowers incoming pressure but doesn’t accommodate the extra volume from thermal expansion.