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Plumber Red Seal · Question

A potable water heater is installed in a closed system. What device must be installed to protect against excessive pressure due to thermal expansion?

While a T&P valve provides emergency relief, an expansion tank is required to absorb the repeated, normal pressure increases caused by heating water in a closed

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Question: A potable water heater is installed in a closed system. What device must be installed to protect against excessive pressure due to thermal expansion?

Answer options:

  • A temperature and pressure relief valve (T&P valve).
  • A pressure reducing valve (PRV). ✅ A thermal expansion tank or other approved device.
  • A vacuum relief valve.

Correct answer: A thermal expansion tank or other approved device.

Explanation: While a T&P valve provides emergency relief, an expansion tank is required to absorb the repeated, normal pressure increases caused by heating water in a closed system, preventing chronic T&P valve discharge and wear on the system.

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