A commercial kitchen requires a water supply capable of delivering 3.0 L/s for a bank of pot-filling faucets. The available static pressure at the building's main is 550 kPa, and the total equivalent length of the supply piping to the faucets is 60 meters. If using Type L copper tubing, what nominal pipe size is the most appropriate to ensure adequate flow and pressure at the fixture, assuming a maximum velocity of 2.0 m/s and a minimum residual pressure of 140 kPa at the fixture?

Question: A commercial kitchen requires a water supply capable of delivering 3.0 L/s for a bank of pot-filling faucets. The available static pressure at the building's main is 550 kPa, and the total equivalent length of the supply piping to the faucets is 60 meters. If using Type L copper tubing, what nominal pipe size is the most appropriate to ensure adequate flow and pressure at the fixture, assuming a maximum velocity of 2.0 m/s and a minimum residual pressure of 140 kPa at the fixture?

Answer options:

• DN 40 (1 1/2 inch) ✅ DN 50 (2 inch)
• DN 65 (2 1/2 inch)
• DN 80 (3 inch)

Correct answer: DN 50 (2 inch)

Explanation: To deliver 3.0 L/s within the given parameters (especially the velocity limit), a DN 50 copper pipe would typically be required after friction loss calculations. Smaller sizes would result in either exceeding the velocity limit or failing to meet the residual pressure, while larger sizes might be oversized and incur unnecessary cost.