Water Supply and Distribution Systems
Supply System Concepts
Water supply design balances pressure, flow, and sizing. Know the terms: static pressure, residual pressure, friction loss, and developed length. Supply fixture units estimate demand. Learn the difference between a building supply, a main, risers, branches, and fixture supply tubes. Understand backflow prevention and the difference between a vacuum breaker, a check valve, and a reduced-pressure zone assembly.
Materials and Sizing
Know common materials (copper, PEX, CPVC, galvanized) and their joining methods. Sizing uses fixture units and tables accounting for pressure loss. Understand that long runs and high elevations reduce available pressure. Learn about water hammer arrestors, thermal expansion, and insulation for freeze protection and energy.
Traps in Questions
Distractors confuse backflow prevention devices and their applications, or assume larger pipe always improves pressure without considering friction. Watch for questions on hot and cold water location (hot on the left facing the fixture), cross-connections, and the need for accessible valves. Another trap: assuming a check valve alone protects a potable supply.
Worked Example
Rule of thumb: "Pressure at the fixture, not at the meter." Subtract friction loss and elevation loss from static pressure to estimate residual pressure. If a fixture needs 8 psi and the estimate falls below that, upsize the pipe or shorten the run.