Plumbing riser diagram review
A checklist for reviewing sanitary, storm, water, and gas riser diagrams
What Riser Diagrams Show
A plumbing riser diagram is a schematic, non-scaled representation of how plumbing systems run vertically through a building. Riser diagrams show how fixtures connect to branches, how branches connect to risers, and how risers connect to the building main. They are essential for verifying fixture unit calculations, venting compliance, and routing feasibility before plans and details are finalized.
The Riser Diagrams You'll Review
- Sanitary waste and vent (DWV) riser
- Storm drainage riser
- Domestic cold water riser
- Domestic hot water and recirculation riser
- Gas piping riser
- Specialty risers: medical gas, lab waste, deionized water, compressed air
Sanitary Riser Review Checklist
- Drainage fixture units (DFU) summed correctly at each branch and stack
- Stack size matches DFU per IPC Table 710.1(2) or UPC equivalent
- Building drain sized for total DFU plus storm if combined
- Vent stack sized per code based on stack size and developed length
- Every fixture vented with appropriate vent type (individual, common, wet, circuit, AAV)
- Stack vent extends through roof with required size
- Cleanouts at base of stacks, at major direction changes, and at intervals along long runs
- P-traps on every fixture with maximum trap arm length not exceeded
- No flat venting and no S-traps
Storm Riser Review Checklist
- Roof area served by each leader within code maximum based on rainfall rate
- Leader size per IPC Table 1106.2 or UPC Table 1101
- Building storm drain sized for total tributary area
- Secondary (overflow) drainage with separate piping to point of discharge
- No combined storm and sanitary unless explicitly permitted
- Cleanouts and inspection openings provided
Domestic Water Riser Review Checklist
- Fixture units (WSFU) summed correctly at each branch and floor
- Pipe size per Hunter's method or equivalent at each point
- Pressure at the highest, most remote fixture meets minimum (typically 8 psi flush valve, lower for ball valves)
- Pressure-reducing valve sized and located if static pressure exceeds 80 psi
- Backflow preventers at all required locations
- Isolation valves at each floor and major branch
- Hot water recirculation loop shown with proper return path
- Expansion tank or expansion device for closed systems
Gas Riser Review Checklist
- Total connected gas load (MBH) accurate
- Pipe size per IFGC Table 402.4 based on length and load
- Shutoff valves at each appliance and at the meter
- Sediment traps at appliance connections per code
- Drip legs at low points
- Routing avoids structural elements, electrical equipment, and HVAC equipment per code
- CSST bonding requirements documented
Always cross-check the riser diagram against the plumbing plan and the fixture schedule. A discrepancy between the fixture count on the plan and the fixture unit totals on the riser is the most frequent plumbing review finding. Riser diagrams are often the first thing updated and the last thing reviewed.
Common Riser Diagram Errors
- Fixture units summed in floors but not added to the stack total
- Stack size matches fixture units but ignores branch interval limit
- Vent stack size based only on diameter, not on developed length
- Wet venting limits exceeded
- Trap arm length exceeds maximum for trap size
- Hot water recirculation return not shown on the riser
- Gas pipe sizing based on connected load instead of demand
- Storm leader sized for design rainfall but not for overflow scenario
Keep exploring
Related references for plumbing drawing review.