WSFU Reference — FPC Table 604.3
| Fixture | Private (WSFU) | Public (WSFU) |
|---|---|---|
| Toilet (flush tank) | 2.5 | 5.0 |
| Toilet (flushometer) | 6.0 | 10.0 |
| Lavatory / bathroom sink | 1.0 | 2.0 |
| Bathtub (with shower) | 2.0 | 4.0 |
| Shower stall | 2.0 | 4.0 |
| Kitchen sink | 1.5 | 3.0 |
| Dishwasher (domestic) | 1.5 | — |
| Laundry tray | 1.5 | 3.0 |
| Washing machine | 3.0 | — |
| Hose bib (sillcock) | 2.5 | 5.0 |
| Urinal (flush tank) | — | 3.0 |
| Service sink | 3.0 | 3.0 |
| Bar sink | 1.0 | 2.0 |
| Ice maker | 0.5 | 1.0 |
| Water softener | 1.0 | — |
Supply Pipe Sizing — FPC Table 604.4
| Total WSFU | Min Pipe Size | Typical Use |
|---|---|---|
| Up to 3 | 1/2 inch | Single fixture branch |
| 4–6 | 3/4 inch | Small bath group |
| 7–15 | 3/4 inch | Small residence |
| 16–30 | 1 inch | Medium home |
| 31–60 | 1-1/4 inch | Large home / small commercial |
| 61–100 | 1-1/2 inch | Multi-bath commercial |
| 101–180 | 2 inch | Medium commercial |
| 181–300 | 2-1/2 inch | Large commercial |
| 301+ | 3 inch + | Large commercial / multi-family |
FL note: FL pressure averages 65–75 PSI at the meter. Homes with street pressure under 50 PSI (common in older South FL): pipe one size up from table minimum to compensate for pressure loss at peak demand.
DFU Reference — FPC Table 702.1
| Fixture | DFU Value | Trap Size |
|---|---|---|
| Toilet | 4 | 3" |
| Lavatory / sink | 1 | 1-1/4" |
| Bathtub | 2 | 1-1/2" |
| Shower stall | 2 | 2" |
| Kitchen sink | 2 | 1-1/2" |
| Dishwasher | 2 | (connects to KS) |
| Washing machine | 3 | 2" |
| Laundry tray | 2 | 1-1/2" |
| Floor drain | 2 | 2" |
| Urinal (wall hung) | 4 | 2" |
| Service sink | 3 | 3" |
| Bar / prep sink | 1 | 1-1/2" |
Drain Pipe Sizing — FPC Table 702.3 (1/4" per foot slope)
| Pipe Size | Max DFU (Horiz) | Max DFU (Stack) | Max DFU (Building) |
|---|---|---|---|
| 1-1/4" | 1 | 2 | — |
| 1-1/2" | 3 | 4 | — |
| 2" | 6 | 10 | — |
| 2-1/2" | 12 | 20 | — |
| 3" | 20 | 48 | 36 |
| 4" | 160 | 240 | 216 |
| 5" | 360 | 540 | 480 |
| 6" | 620 | 960 | 840 |
Vent Pipe Sizing — FPC Table 906.1
| Drain Pipe Size | Min Vent Size | Max Vent Length |
|---|---|---|
| 1-1/4" | 1-1/4" | 45 ft |
| 1-1/2" | 1-1/4" | 60 ft |
| 2" | 1-1/2" | 120 ft |
| 3" | 2" | 180 ft |
| 4" | 3" | 212 ft |
| 6" | 4" | 300 ft |
FL slab homes note: Most FL homes are slab-on-grade — DWV under-slab runs are cast before the pour and cannot be easily changed. Verify existing under-slab drain sizes before adding fixtures. Adding a bathroom to a FL slab home requires saw-cutting and breaking the slab.
FPC 2023 Key Sizing Code Sections
| Section | Topic | Key Rule |
|---|---|---|
| §604.1 | Supply sizing general | Size per WSFU Table 604.3; velocity max 8 ft/sec |
| §604.3 | Fixture unit table | WSFU by fixture, private vs public |
| §604.4 | Supply pipe sizing | Pipe diameter by total WSFU |
| §604.6 | Velocity limits | Max 8 ft/sec supply; max 4 ft/sec final branch |
| §604.8 | Pipe support | Copper horizontal 6 ft max; vertical 10 ft max |
| §701.1 | DWV general | Gravity drainage unless approved ejector |
| §702.1 | DFU fixture table | Fixture unit values |
| §702.3 | Drain pipe sizing | Diameter by DFU |
| §706.3 | Drain slope | Min 1/4" per foot for 3" and smaller; 1/8" for 4"+ |
| §708.1 | Cleanout access | At base of each stack and each 100 ft horizontal |
| §906.1 | Vent pipe sizing | Min vent by drain served; max length per §906 |
| §912.1 | Wet venting | Permitted residential with limits |
Most Common FL Pipe Sizing Violations
- 3/4" supply main to full house: Many 1970s–1990s FL homes have undersized 3/4" copper mains; adding fixtures now triggers sizing upgrades.
- S-traps: Prohibited (self-siphon risk); flagged during any WH or repipe permit.
- 2" drain for 3 toilets: Each toilet 4 DFUs; a 2" horizontal drain maxes at 6 DFUs. Three toilets (12 DFUs) require a 4" drain.
- No cleanout at stack base: FPC §708 requires a cleanout at the base of each stack within 2 feet.
- ABS pipe: Prohibited in Florida — PVC Schedule 40 or DWV required.
- Vent too small or missing: In FL slab homes venting is often inadequate; wet venting per §912 offers a workaround.
Commercial — County-Specific Notes
| County | Commercial Notes |
|---|---|
| Miami-Dade | Structural engineer-stamped plans for commercial over $25K; separate MEP review; water dept approval for mains >2" |
| Broward | Fire suppression + plumbing submitted together; grease interceptor sizing requires Health Dept sign-off for food service |
| Hillsborough | Tampa Water Dept approval for backflow on commercial mains; permits via HCBCC portal; plan review 10–14 days |
| Orange | Separate plumbing plan submittal; OC Utilities must approve tap for water service above 1" |
| Palm Beach | Commercial WH and supply pipe require licensed Mechanical and Plumbing Engineer of Record stamp |
Typical FL Residential Fixture Unit Loads
| Home Type | Typical WSFUs | Typical DFUs | Min Supply Main |
|---|---|---|---|
| 2BR/1BA condo | 12–16 | 14–18 | 3/4" |
| 3BR/2BA single family | 20–28 | 22–32 | 1" |
| 4BR/3BA single family | 28–40 | 30–45 | 1–1-1/4" |
| 5BR/4BA large home | 40–60 | 45–65 | 1-1/4–1-1/2" |
| Duplex (each unit) | 20–30 | 22–35 | 1" per unit |
| Small commercial (1 restroom) | 20–35 | 25–40 | 1–1-1/4" |