Drain Capacity Reference (FPC Table 710.1)
| Pipe Size | 1/8" slope | 1/4" slope | 1/2" slope |
|---|---|---|---|
| 1½" | 1 DFU | 3 DFU | 5 DFU |
| 2" | 8 DFU | 14 DFU | 21 DFU |
| 2½" | 24 DFU | 42 DFU | — |
| 3" | 48 DFU | 84 DFU | — |
| 4" | 144 DFU | 250 DFU | — |
| 5" | 240 DFU | 425 DFU | — |
| 6" | 400 DFU | 700 DFU | — |
| 8" | 1,100 DFU | 1,920 DFU | — |
Vent Sizing Reference (FPC Table 916.1)
FPC 904.1: Every trap and trapped fixture shall be vented. FPC 906.1: Vent pipe shall not be less than 1¼" and not less than ½ the diameter of the drain it serves.
| Drain Size | Min Vent | Max DFU on Vent | Max Vent Length |
|---|---|---|---|
| 1¼" drain | 1¼" | 1 DFU | 45 ft |
| 1½" drain | 1¼" | 4 DFU | 60 ft |
| 2" drain | 1½" | 10 DFU | 120 ft |
| 3" drain | 2" | 30 DFU | 180 ft |
| 4" drain | 3" | 100 DFU | 212 ft |
| 5"+ drain | 4" | 300+ DFU | 300 ft |
FPC 903.1 — FL roof vent termination: min 6" above roof; in Miami-Dade/Broward HVHZ, vent flashing must be product-approved per FBC 1714.5. FPC 908 — Wet venting: permitted for single bathroom groups; 2" wet vent serves 1-3 fixtures, 3" wet vent up to 6; common in FL slab construction.
FPC DWV Code — Key Requirements
Chapter 7 — Sanitary Drainage: - FPC 701.1: DWV conveys sewage/liquid wastes to public sewer or approved private disposal; FL requires FL-licensed plumbing contractor for all DWV work. - FPC 704.1 — Slope: horizontal piping at not less than ¼" per foot (2%) for pipes 3" and smaller; 4"+ may slope at ⅛" per foot minimum (1.04%). - FPC 704.2 — Minimum size: no horizontal waste/soil pipe smaller than the largest trap it serves; minimum 3" for water closets and urinals. - FPC 704.3 — Change of direction: use 45° wyes or combo fittings; no 90° sanitary tees in horizontal-to-horizontal runs; no double sanitary tees. - FPC 707.1 — Prohibited fittings: running traps, double-hub used backwards, bell-and-spigot on PVC without approved coupling, copper fittings with lead joints.
Chapter 9 — Vents: - FPC 901.1: every trap and trapped fixture shall be vented. - FPC 904.1: AAVs permitted (FPC 918) for individual fixtures/branch vents; prohibited as the only vent on a stack; must be accessible (ASSE 1051 island fixtures / ASSE 1049).
Trap Arm Lengths (FPC 909.2)
Max distance from trap to vent:
| Trap Size | Max Trap Arm | Slope Required |
|---|---|---|
| 1¼" | 2.5 ft | ¼" per foot |
| 1½" | 3.5 ft | ¼" per foot |
| 2" | 5.0 ft | ¼" per foot |
| 3" | 6.0 ft | ¼" per foot |
| 4" and larger | 10.0 ft | ⅛" per foot |
DWV Inspection Checklist
- All horizontal drains sloped ¼" per foot (3" and smaller); ⅛" per foot min for 4"+ (FPC 704.1)
- No prohibited fitting types; use 45° wyes/combo fittings (FPC 704.3)
- Water closet drain minimum 3" diameter (FPC 704.2)
- Trap arm lengths within FPC 909.2 limits
- Every trap and fixture properly vented (FPC 901.1/904.1; AAVs per 918 with access panel)
- Vent pipe minimum ½ of drain diameter (min 1¼"; FPC 906.1)
- Cleanouts per FPC 708 — max 100 ft spacing; at each 90° change (FPC 708.4)
- DWV pressure test (5-psi air or 10-ft water head) before covering (FPC 312.2); rough-in inspection before slab pour
- FL plumbing permit pulled for all DWV work (FBC 105.1)
FL DWV Pipe Materials / Slab Notes
Approved DWV materials (FPC Chapter 6): PVC DWV Sch 40 (ASTM D2665); ABS DWV (ASTM D2661); cast iron hub-and-spigot and hubless (CISPI 301); copper DWV (ASTM B306); galvanized steel (ASTM A53, existing only). PEX and CPVC are NOT approved for DWV in Florida. FL slab construction: under-slab inspection required before pour in most counties; rough-in inspection separate from final; Miami-Dade requires separate MEP inspections; no PVC exposed above ground unless UV-rated/protected; cleanout required at/near foundation (FPC 708.5).