Plumber Red Seal · Question
A 50-gallon residential electric water heater is installed on a system with a backflow preventer at the service entrance. What component is essential to prevent damage from thermal expansion?
When water is heated, it expands. In a closed system (created by the backflow preventer), this expansion increases pressure significantly, which can damage the
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Question: A 50-gallon residential electric water heater is installed on a system with a backflow preventer at the service entrance. What component is essential to prevent damage from thermal expansion?
Answer options:
- A pressure-reducing valve
- An oversized temperature and pressure relief valve
- A water hammer arrestor ✅ A potable water expansion tank
Correct answer: A potable water expansion tank
Explanation: When water is heated, it expands. In a closed system (created by the backflow preventer), this expansion increases pressure significantly, which can damage the water heater and fixtures. A thermal expansion tank is required to absorb this expanded water volume safely.
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