What is the size of the domestic cold water supply noted for the scenario associated with the entry labeled 'question 6'?

• A. 1-1/4 inches
• B. 3/4 inch
• C. 1 inch
• D. 1-1/2 inches

Answer: (B)

In domestic plumbing, the cold-water supply feeding a typical residential appliance (like a water heater) uses a 3/4 inch connection. This size is standard because it provides enough flow to meet normal hot-water demand without carrying the extra cost and potential pressure drop of a larger line. A 1/2 inch line is usually too small for a main cold inlet to a heater and can limit flow, while sizes like 1 inch or larger are generally used for main service or multi-fixture runs, not just a single heater. Therefore, 3/4 inch is the appropriate choice for the domestic cold water supply in this scenario.