NASCLA Accredited Commercial General ContractorMechanical, Electrical, Plumbing (MEP)Easy
A plumbing contractor is installing a new water heater in a commercial building. The local code requires a thermal expansion tank for closed-loop hot water systems. What is the primary purpose of installing a thermal expansion tank?
- ATo increase the water pressure in the system.
- BTo prevent backflow of contaminated water.
- CTo filter sediment from the incoming water supply.
- DTo absorb the increased volume of water caused by heating.
Show answer & explanationAnswer & explanation
Correct answer: D. To absorb the increased volume of water caused by heating.
When water is heated, it expands. In a closed-loop system, this expansion can lead to excessive pressure, which a thermal expansion tank absorbs to protect the system components.
Why the other options are wrong
- A. Expansion tanks do not increase water pressure; they regulate it by absorbing excess volume.
- B. Backflow preventers, not expansion tanks, are used to prevent backflow.
- C. Sediment filters are used for filtering, not expansion tanks.
Thermal Expansion Tank
A device installed in a closed-loop hot water system to absorb the volumetric expansion of water as it is heated, preventing excessive pressure buildup and protecting system components.
- Required for closed-loop hot water systems.
- Protects water heaters and plumbing fixtures.
- Contains a diaphragm and air cushion.
Memory trick: Hot Water Expands, Tank Absorbs, Pressure Drops.