A homeowner reports that their hot water tank is leaking from the pressure relief valve. Upon inspection, you notice water dripping steadily from the discharge pipe of the T&P (temperature and pressure) relief valve, and the hot water tank is visibly bulging slightly at the top. What is the most likely cause of this issue?

Question: A homeowner reports that their hot water tank is leaking from the pressure relief valve. Upon inspection, you notice water dripping steadily from the discharge pipe of the T&P (temperature and pressure) relief valve, and the hot water tank is visibly bulging slightly at the top. What is the most likely cause of this issue?

Answer options: ✅ The expansion tank is undersized or waterlogged.

• The water heater's thermostat is set too low.
• There is a blockage in the hot water supply line.
• The cold water shut-off valve is partially closed.

Correct answer: The expansion tank is undersized or waterlogged.

Explanation: Leakage from a T&P relief valve and a bulging tank are classic symptoms of excessive pressure due to thermal expansion that is not being adequately absorbed. A waterlogged or undersized expansion tank cannot absorb this expansion, leading to high pressure and relief valve activation. A low thermostat setting would result in cooler water, not overpressure. Blockages in supply lines or partially closed valves do not typically cause this type of overpressure.