A plumber is called to a new apartment building where residents are complaining of low hot water pressure at fixtures on the upper floors, even though cold water pressure is adequate throughout. The building has a central hot water plant. What is the most likely issue?

Question: A plumber is called to a new apartment building where residents are complaining of low hot water pressure at fixtures on the upper floors, even though cold water pressure is adequate throughout. The building has a central hot water plant. What is the most likely issue?

Answer options:

• The hot water recirculation pump is undersized. ✅ The hot water supply piping for the upper floors is inadequately sized.
• The expansion tank for the hot water system is too small.
• There is excessive sediment build-up in the hot water heater.

Correct answer: The hot water supply piping for the upper floors is inadequately sized.

Explanation: If cold water pressure is adequate but hot water pressure is low only on upper floors, it suggests a problem specific to the hot water distribution to those floors, with undersized piping being a common culprit. An undersized recirculation pump wouldn't directly affect pressure, and expansion tank size relates to thermal expansion, not flow pressure.