A 32-story residential tower case study — a worked pressure-zone breakdown bounded by both a 45 psi minimum and an 80 psi code ceiling, booster pump sizing carried from Module 6's shortfall method, the counterintuitive way PRV coverage grows at higher zones, and independent riser sizing per zone.
The project brief: a 32-story, 128-unit residential high-rise has only 65 psi net static pressure available at its service entrance after meter and backflow-preventer losses — nowhere near enough to reach the top floor on street pressure alone. This module works through the four decisions a domestic water riser design for a building this height actually requires: how many pressure zones the building needs and where they break, how each zone's booster pump is sized, where pressure-reducing valves have to sit to protect each zone's lower floors, and how each zone's riser is sized to its own demand.
The zone-by-zone worked numbers reveal a genuinely counterintuitive result: pressure-reducing valve coverage grows, not shrinks, at greater height, because each successively higher zone's pump has to generate more shutoff head to reach its own top floor — and that added head shows up as excess pressure at the same zone's own lowest floors. The full worked calculations, complete bill of materials, and finished design reasoning are part of the unlocked module below.