Velocity limits and friction/pressure loss calculation, using fixture unit tables and pipe sizing charts together, sizing for actual peak demand, and the pipe sizing mistakes that most often surface as a low-pressure top floor or a hammering riser after occupancy.
Pipe sizing is a constrained optimization, not a single lookup: a pipe has to be large enough to deliver adequate flow and pressure at peak demand, small enough to keep velocity inside limits that prevent noise, erosion, and water hammer, and small enough to stay economical to install and insulate. This module works through the two technical inputs every sizing decision depends on — velocity limits and friction loss, including the equivalent length of fittings most new designers underestimate — and the methodology that combines them with Module 3's fixture unit data to size a real system against its actual peak demand.
A full worked example checks residual pressure at a building's most remote fixture, including elevation loss, fitting equivalent length, and water meter and backflow preventer losses — the exact calculation Module 6's booster pump sizing picks up where this module leaves off.