A plumber is sizing the copper tubing for a hot water recirculation system in a commercial kitchen. The system needs to deliver 0.5 L/s of hot water to a fixture 45 metres away with a maximum allowable pressure drop of 50 kPa. Using a friction loss chart for Type L copper tubing, what is the smallest nominal pipe size that will meet these requirements?

Question: A plumber is sizing the copper tubing for a hot water recirculation system in a commercial kitchen. The system needs to deliver 0.5 L/s of hot water to a fixture 45 metres away with a maximum allowable pressure drop of 50 kPa. Using a friction loss chart for Type L copper tubing, what is the smallest nominal pipe size that will meet these requirements?

Answer options: ✅ 19 mm (3/4")

• 25 mm (1")
• 32 mm (1 1/4")
• 38 mm (1 1/2")

Correct answer: 19 mm (3/4")

Explanation: To solve this, one would typically use a friction loss chart or table. For a flow of 0.5 L/s and a pressure drop of 50 kPa over 45 metres (which translates to approximately 1.1 kPa/m), a 19 mm (3/4") Type L copper tube would be the smallest size able to maintain the required flow within the allowable pressure drop. Larger sizes would provide more flow but are not the smallest required.