A residential hot water supply system delivers water at 55°C, but residents complain of inadequate hot water pressure at the shower head. The cold water pressure at the main is 480 kPa, and the hot water tank is located on the ground floor with the shower on the second floor, 4.5 metres above. What is a likely cause of the low hot water pressure?

Question: A residential hot water supply system delivers water at 55°C, but residents complain of inadequate hot water pressure at the shower head. The cold water pressure at the main is 480 kPa, and the hot water tank is located on the ground floor with the shower on the second floor, 4.5 metres above. What is a likely cause of the low hot water pressure?

Answer options:

• Excessive pipe length reducing cold water pressure before the heater.
• Increased velocity due to higher temperature in the hot water lines. ✅ Static head loss due to elevation, impacting hot water pressure.
• The expansion tank is undersized, causing pressure fluctuations.

Correct answer: Static head loss due to elevation, impacting hot water pressure.

Explanation: Static head loss due to elevation directly reduces pressure in a plumbing system. For every metre of elevation, there is a pressure loss of approximately 9.8 kPa. Therefore, a 4.5-metre elevation difference would result in a significant pressure drop for the hot water at the shower, leading to low apparent pressure.