Which considerations are essential when selecting pipe sizes for a multi-story building's cold water system?

• A. Peak demand, vertical elevation losses, friction losses, farthest fixture pressure, and use hydraulic calculations or code tables to determine sizes and PRV placements.
• B. Only pipe length and color.
• C. Only number of fixtures, ignoring elevation.
• D. Only the material cost of pipe.

Answer: (A)

Selecting pipe sizes for a multi-story cold-water system is about meeting the hydraulic needs of the entire building rather than just how long the pipes are or what they look like. You have to account for peak demand so the system can deliver enough flow when many fixtures run at once. Vertical elevation losses matter because water has to be pumped and pressurized up to higher floors, so pressure drops as you rise. Friction losses accumulate along straight runs and fittings, reducing pressure the farther water travels. The farthest fixture (often the highest point) is most at risk of low pressure, so you size for adequate pressure there and place pressure-reducing valves or pressure zones as needed to keep pressures within code limits. Using hydraulic calculations or code tables ensures the selected diameters provide sufficient flow and pressure while controlling losses; it also helps determine where PRVs should be placed and how the system is zoned.

Focusing on pipe length and color ignores flow capacity and pressure needs. Looking only at the number of fixtures while ignoring elevation misses pressure changes due to height. Considering only material cost neglects whether the chosen sizes will actually meet demand and code requirements.