FPC Table 709.1 fixture units, horizontal drain sizing, trap arm limits, and slope drop
FPC 2023 COMPLIANTCount fixtures on this drain branch — DFU values auto-populate.
| 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 | — |
FPC 904.1: Every trap and trapped fixture shall be vented.
FPC 906.1 — Vent pipe minimum size: Shall not be less than 1¼" and not less than ½ the diameter of the drain it serves.
FPC 916.1 — Individual vent sizes:
| 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: Vent shall extend min 6" above roof in FL. In Miami-Dade/Broward HVHZ, vent flashing must be product-approved per FL Building Code 1714.5.
FPC 908 — Wet venting: Permitted in FL for single bathroom groups. 2" wet vent serves 1–3 fixtures; 3" wet vent serves up to 6 fixtures. Common in FL slab construction.
FPC 701.1 — Scope: DWV system shall convey sewage and liquid wastes to public sewer or approved private disposal system. FL requires FL-licensed plumbing contractor for all DWV work.
FPC 704.1 — Slope: Horizontal drainage piping shall be run in practical alignment and a uniform slope of not less than ¼ unit vertical per foot (2%) for pipes 3" and smaller. Pipes 4" and larger may be sloped at ⅛" per foot minimum (1.04%).
FPC 704.2 — Minimum size: No horizontal waste or soil pipe shall be smaller than the largest trap discharge it serves. Minimum 3" for water closets and urinals.
FPC 704.3 — Change of direction: Horizontal-to-vertical changes shall use 45° wyes or combo fittings. No 90° sanitary tees in horizontal-to-horizontal runs. No double sanitary tees.
FPC 707.1 — Prohibited fittings: Prohibited in DWV: running traps, double-hub fittings used backwards, bell-and-spigot on PVC without approved coupling, copper fittings with lead joints.
FPC 901.1 — Venting required: Every trap and trapped fixture shall be vented in accordance with this chapter.
FPC 904.1 — Air admittance valves (AAV): Permitted in FL under FPC 918 for individual fixtures and branch vents. AAVs prohibited as the only vent on a drainage stack. Must be accessible and installed per ASSE 1051 (island fixtures) or ASSE 1049.
FPC 909.2 — Trap arm lengths (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 |
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Costs vary by scope, home size, and your Florida region. Use the calculator above for a Florida-specific estimate rather than a one-size-fits-all price.
Pricing depends on the size and layout of your home, the pipe materials and fixtures you choose, your Florida region and local labor rates, and permit fees. Work that is more complex or harder to access generally costs more.
In Florida, minor maintenance may be DIY, but anything beyond that generally calls for a licensed plumber, and many jobs require a permit and inspection. When a permit, or your main water or drain lines are involved, hire a Florida-licensed plumber.
It depends on the cause and your specific policy. Sudden, accidental damage is more often covered than gradual wear-and-tear or maintenance - confirm the details with your insurer.
Timelines depend on scope - many routine jobs take a few hours to a day, while larger projects run longer. Your licensed plumber can confirm after assessing your home.
Planning estimate, not a quote — confirm with a licensed Florida plumber. Confidence is qualitative: ranges reflect this page’s Florida assumptions, not a guaranteed price.
Estimates on this page are Florida-specific and reflect DWV Drain Sizing for typical Florida homes.
From this page: Costs vary by scope, home size, and your Florida region. Use the calculator above for a Florida-specific estimate rather than a one-size-fits-all price.
Your actual cost depends on your home's condition, layout, and local labor and permit rates.
From this page: Pricing depends on the size and layout of your home, the pipe materials and fixtures you choose, your Florida region and local labor rates, and permit fees. Work that is more complex or harder to access generally costs more.
Generally raises cost: harder access, older homes, added permits and inspections, premium fixtures or materials, and emergency or after-hours work.
Generally lowers cost: easy access, bundling several items in one visit, standard fixtures, and off-peak scheduling.
Curated Florida tools and resources related to this page.
Last reviewed: July 1, 2026 (US Eastern)
Reviewed by the FL Plumbing Tools editorial team.
Sources: Florida plumbing cost research and Florida Building Code / local authority-having-jurisdiction (AHJ) permit references.
Florida reference: Estimates and guidance reflect Florida labor rates, permitting, hard water, humidity, and coastal conditions.
Updates: Reviewed periodically and updated as Florida codes, permit fees, and market rates change.