Journeyman Plumber ExamWater Supply SystemsEasy
A plumber is installing a potable water heater in a residential garage. The local code requires a thermal expansion tank. What is the primary purpose of installing this tank?
- ATo prevent excessive pressure buildup in the water heater and distribution system.
- BTo re-circulate hot water more efficiently throughout the home.
- CTo filter sediment and impurities from the incoming cold water supply.
- DTo increase the hot water delivery pressure to fixtures.
Show answer & explanationAnswer & explanation
Correct answer: A. To prevent excessive pressure buildup in the water heater and distribution system.
Thermal expansion tanks are crucial for safely managing the pressure increase that occurs when water is heated in a closed system. As water heats, it expands, and without an expansion tank, this expansion can lead to dangerously high pressures.
Why the other options are wrong
- B. Recirculation is handled by a different system; expansion tanks are not involved in water movement.
- C. Sediment filtering is done by a filter, not a thermal expansion tank.
- D. Expansion tanks do not increase delivery pressure; they manage excess pressure.
Thermal Expansion Tank
A device designed to absorb the increase in volume of water as it heats up in a closed plumbing system, preventing excessive pressure buildup.
- Contains a diaphragm that separates air from water.
- Protects water heaters, pipes, and fixtures from high pressure.
- Required in closed water systems where a backflow preventer or pressure reducing valve is installed.
Memory trick: When water heats, it expands; the tank gives it space to dance.