What is the size of the domestic cold water supply noted for the scenario associated with the entry labeled 'question 10'?

What is the size of the domestic cold water supply noted for the scenario associated with the entry labeled 'question 10'?

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

Answer: (B)

Sizing the domestic cold water supply is all about meeting peak demand without letting pressure collapse along the run. The pipe must be large enough so that when multiple fixtures are used at the same time, the flow remains adequate and the pressure at each outlet stays within acceptable limits. In this scenario, the notes call for a 1-1/4 inch feed. That size helps keep friction losses low over the distance to the farthest fixtures and provides enough flow for simultaneous use, which smaller lines would struggle to deliver. A 3/4 inch line is typically suitable for a single fixture or a very short run, while 1 inch might be marginal for a modest home with several fixtures, and 1-1/2 inch is usually more than what’s needed for a standard dwelling. So the 1-1/4 inch size is chosen as the right balance to meet the demand in that setup.

Sizing the domestic cold water supply is all about meeting peak demand without letting pressure collapse along the run. The pipe must be large enough so that when multiple fixtures are used at the same time, the flow remains adequate and the pressure at each outlet stays within acceptable limits. In this scenario, the notes call for a 1-1/4 inch feed. That size helps keep friction losses low over the distance to the farthest fixtures and provides enough flow for simultaneous use, which smaller lines would struggle to deliver. A 3/4 inch line is typically suitable for a single fixture or a very short run, while 1 inch might be marginal for a modest home with several fixtures, and 1-1/2 inch is usually more than what’s needed for a standard dwelling. So the 1-1/4 inch size is chosen as the right balance to meet the demand in that setup.