A plumber is troubleshooting a low hot water pressure issue in a single-family dwelling. The cold water pressure at the main is 480 kPa, but at the hot water fixture, it drops significantly. After checking the hot water tank and finding no issues, the plumber suspects an issue with the piping. Which of the following would be the most likely cause of localized low hot water pressure if the cold water supply to the tank is adequate?

Question: A plumber is troubleshooting a low hot water pressure issue in a single-family dwelling. The cold water pressure at the main is 480 kPa, but at the hot water fixture, it drops significantly. After checking the hot water tank and finding no issues, the plumber suspects an issue with the piping. Which of the following would be the most likely cause of localized low hot water pressure if the cold water supply to the tank is adequate?

Answer options:

• An undersized hot water recirculation pump ✅ Excessive internal scale buildup in the hot water line
• A malfunctioning pressure reducing valve on the cold water main
• A clogged aerator on the cold water faucet

Correct answer: Excessive internal scale buildup in the hot water line

Explanation: Excessive internal scale buildup in the hot water line significantly reduces the effective internal diameter of the pipe, leading to increased friction loss and a notable drop in pressure at the fixture. An undersized recirculation pump affects circulation, not direct pressure to the fixture, and a malfunctioning PRV on the cold main would affect both hot and cold pressures. A clogged aerator on the cold water faucet would only affect cold water at that specific faucet.