A 23-section interactive guide to plumbing system design — Water Supply Fixture Unit (WSFU) sizing and Hunter's Curve demand calculations, drain-waste-vent (DWV) and roof drainage design, hot water recirculation and storage/recovery sizing, commercial and multi-story riser design, facility-specific plumbing plans across residential, medical, retail, and industrial occupancies, and MEP coordination, inspection, and commissioning. Every reference drawing gets its own full-size slide so schedules, riser diagrams, and worked examples stay legible.
Chapters 1–4 build the water supply foundation: PEX home-run distribution, WSFU pipe sizing through Hunter's Curve, a fully worked fixture-unit calculation, and reading a pressure-loss waterfall through a supply system. Chapters 5–7 cover drain-waste-vent design and roof drainage: DWV riser diagrams, trap seals and venting, coordinated supply/DWV rough-in, and primary/overflow roof drainage. Chapters 8–9 cover hot water systems: recirculation loop design and water heater storage-versus-recovery-rate sizing. Chapters 10–13 cover commercial and multi-story riser design: service entrance/RPZ/booster pump/PRV sequencing, a full four-system commercial schematic, multi-story DWV stack sizing with circuit venting, and apartment building supply risers. Chapters 14–20 apply the fundamentals to seven facility types: private wells, a bathroom remodel, and commercial, kitchen, medical, retail, and industrial plumbing plans. Chapters 21–23 close with MEP ceiling coordination, the code-required inspection sequence, and the full system commissioning sequence.
Use the Prev / Next buttons at the bottom, or press the arrow keys on your keyboard. Click the ☰ menu button in the top-right to open the table of contents and jump to any section. Each chapter's reference figure follows immediately after its text as its own dedicated slide, so you can view the full diagram, schedule, or chart at a readable size before moving to the next chapter.
Plumbing designers and engineers who want a structured, code-referenced walkthrough of fixture-unit sizing, DWV design, and riser layout; contractors and estimators coordinating rough-in against real commercial and residential drawing sets; and engineering and trades students studying for licensure who need IPC/UPC/ASSE/ASME/NSF-referenced explanations tied directly to real system diagrams rather than abstract code text alone.
A WSFU is a weighted demand factor assigned to each fixture type (per UPC Table 604.3 / IPC Table E103.3(2)) that accounts for flow rate and the odds of simultaneous use. Total WSFU load is summed per branch or building, then converted to a peak design GPM using Hunter's Curve, and that GPM is used to size the pipe against the code's friction-loss and velocity tables.
A DWV riser carries waste down a soil stack to the building drain while a vent branch admits air so each fixture's trap seal is never siphoned dry. Stack diameter is sized to the cumulative drainage fixture unit (DFU) load of every floor above a given point, and fixtures can be individually vented or grouped on a circuit vent that connects above the highest fixture's flood-level rim.
In buildings with long hot-water runs, water sitting in the supply pipe cools between draws, wasting water and time. A recirculation system adds a dedicated return riser and pump (with a check valve to prevent thermosiphoning) that continuously circulates hot water so it's already near every fixture, with balancing valves at each floor to equalize flow contribution across the loop.
It traces the five-stage sequence from the city main to the building's risers: the water meter, an RPZ backflow preventer (ASSE 1013) protecting the public supply, a variable-speed booster pump set for buildings where main pressure is insufficient, and a pressure-reducing valve station that creates pressure zones so upper and lower floors both receive appropriate, code-compliant static pressure.
Code-required inspection runs four stages — underground, rough-in, pressure testing, and final — each witnessed by the Authority Having Jurisdiction. Commissioning is a broader eight-step process (startup, visual inspection, pressure testing, functional flow testing, backflow certification, hot water temperature verification, third-party reporting, and owner training/acceptance) that must fully complete before a system is placed into service.
Disclaimer: This guide summarizes general plumbing engineering concepts and illustrative reference drawings for educational purposes only. All projects, facilities, and fixture layouts depicted are illustrative examples, not as-built or approved construction documents. Always consult a licensed plumbing engineer or contractor and the applicable edition of the IPC, UPC, and local plumbing code amendments for actual project design, sizing, and installation.