NSPC Pipe Sizing Guide

The National Standard Plumbing Code (NSPC), formerly the BOCA National Plumbing Code, is used in parts of the northeastern United States. It defines its own WSFU values and flow conversion methods that differ from both IPC and UPC. Plumbing Booster includes NSPC fixture selection tables and flow conversion to support NSPC-compliant designs.

NSPC pipe sizing follows the same general approach as other codes: 1. **Sum WSFU** using NSPC fixture unit tables. 2. **Convert WSFU to flow rate** using NSPC conversion methods. 3. **Select pipe size** based on NSPC sizing tables and velocity limits. 4. **Verify velocity** and compliance. The key difference is the WSFU values themselves - NSPC assigns different fixture unit loads than IPC or UPC for the same fixture types.

Key NSPC references: - **NSPC Fixture Selection Tables** — WSFU values per fixture type and supply control - **NSPC Flow Conversion Tables** — WSFU to GPM/L/s conversion - **NSPC Water Distribution Sizing Tables** — Pipe size selection based on flow and pressure

For a bathroom group under NSPC: - Water closet (flush tank): 4 WSFU cold - Lavatory: 1 WSFU cold, 1 WSFU hot - Bathtub: 2 WSFU cold, 2 WSFU hot - **Total cold = 7 WSFU, Total hot = 3 WSFU** NSPC conversion gives approximately 11 GPM for 7 WSFU. The software selects a 1/2" pipe if velocity is within limits, or upsizes to 3/4" if needed.

Select "NSPC" as the plumbing code in System Structure Configuration. The fixture selection table in Wet Areas automatically switches to NSPC WSFU values. All downstream calculations use NSPC-specific data.