Pipe Sizing
Water supply by fixture units; drainage by DFU.
Example
You enter
- Fixtures fixture lavatory, count 2, and 3 more
- Drain slope 0.25
You get
- Total WSFU 10.5
- Total DFU 12
- Estimated demand 12.3 gpm
- Recommended supply size 1
- Recommended drainage size 3
Details, formula, and sources
Water-supply size from Hunter's Curve fixture units (DFU per IPC 2021 Section 709, Table 709.1); WSFU for water supply per IPC Section 604, Table 604.3.
IPC 2021 (International Plumbing Code). Sections 604, 709, Tables 604.3 and 709.1. Hunter's Curve methodology by name.
Free read-only access at codes.iccsafe.org.
Estimate. AHJ and licensed plumber / gas fitter govern. Verify against the IPC / IFGC edition adopted in your jurisdiction.
Field names used by the API: fixtures, slope_in_per_ft, total_wsfu, total_dfu, estimated_demand_gpm, recommended_supply_size, recommended_drainage_size
- Pressure head at most-distant fixture 8 psi minimum unless user suppliesIPC 2021 Section 604.6
- Maximum velocity 8 fps water supply / 5 fps hot waterIPC 2021 Section 604.4