How Should Plumbing Chases Be Designed in Multi-Story Buildings?

Plumbing chases are vertical cavities designed to carry stacked drain, waste, vent, and water piping through multi-story buildings with proper sizing, alignment, and maintenance access. Good chase design stacks fixtures vertically, sizes piping for the fixture load, coordinates with structure and fire ratings, and provides cleanout access at every level. The chase is where the building's plumbing logic lives. When fixtures stack cleanly and the chase is sized from real piping layouts, installation is straightforward and the system performs for decades. When the chase is an afterthought — sized by guess, threaded around structure, closed up without cleanout access — the building inherits drainage problems, noise problems, and maintenance problems that never fully go away.

Alignment comes first and it's really an architectural decision with engineering consequences: stacking wet rooms vertically so piping runs straight. I push for this in early design because once floor plans are set with scattered plumbing, the chase design becomes damage control instead of design. Sizing and access come next. Drain, waste, and vent piping gets sized for the fixture units on each stack, water risers for the demand, and the chase gets drawn at installation scale with fittings, insulation, and offsets. Cleanouts go at the base of stacks and at required intervals, positioned where a technician can actually reach them. And the whole assembly gets coordinated with structure (no compromised members) and fire protection (rated penetrations detailed and inspected).

Plumbing is the least forgiving system to fix after the walls close. These rules keep chases honest.

• Stack wet rooms vertically: straight piping outperforms offset piping in every way that matters
• Size from real layouts: draw the piping at installation scale with fittings, insulation, and offsets
• Provide cleanout access: every stack base and required interval, reachable without demolition
• Coordinate structure and fire rating: no compromised members, rated penetrations detailed and inspected
• Design for quiet: pipe material, insulation, and chase construction selected for the building's acoustic needs