FL Tankless Sizing Reference
FL Groundwater Temps: South FL 73°F avg -> dT ~47°F to 120°F | Central FL 70°F -> dT 50°F | North FL 67°F -> dT 53°F | Panhandle 65°F -> dT 55°F
Rule of thumb: 1 GPM requires ~2,100 BTU/hr for each degree F of temperature rise (1 GPM x dT x 500 x 8.33 / 60 x efficiency).
Tankless BTU formula: Required BTU/hr = GPM x 500 x dT x 8.33 / 60 where dT = desired output temp minus groundwater inlet temp. Example: 5 GPM x 500 x 50 x 8.33 / 60 = 173,542 BTU/hr needed (Central FL, 120F output).
FL Water Conservation Compliance
FL Showerhead Flow Limits (FPC 604.4)
| Fixture | Max GPM (FL) | WaterSense | IECC Resid |
|---|---|---|---|
| Showerhead | 2.0 GPM @ 80 psi | 1.5–1.8 GPM | 2.0 GPM |
| Body spray | 0.5 GPM each | 0.5 GPM | — |
| Handshower | 2.0 GPM @ 80 psi | 1.5 GPM | 2.0 GPM |
| Bathtub filler | 4.0 GPM | — | 4.0 GPM |
| Multiple showerheads | 2.0 GPM total | Per FPC exception |
FPC 604.4 Exception: Where more than one showerhead is controlled by a single valve, the aggregate flow rate of all heads shall not exceed 2.0 GPM at 80 psi unless each outlet has a separate shutoff — then each outlet is rated individually.
Body Spray Exception: FPC Section 604.4.2 — each body spray panel outlet rated individually at 0.5 GPM max. A 16-jet panel = 8.0 GPM aggregate is code-compliant if each head is <=0.5 GPM. Thermostatic valve required for systems with body sprays to prevent scalding.
Shower drain sizing (FPC Table 709.1): 2" drain = 2.9 GPM max; 3" = 4.6 GPM max; 4" = 8.0 GPM max. Recommend 3" for 3-6 GPM systems; 4" for 6+ GPM or body spray panels.
SFWMD Rule 40E-22 requires WaterSense-labeled showerheads in new construction in SFWMD jurisdiction (Lee, Collier, Hendry, Glades, Palm Beach, Martin, St Lucie, Okeechobee, Broward, Miami-Dade, Monroe).
Permit Requirements — FL Master Shower
When a permit IS required (FBC/FPC): - Adding or relocating any water supply line - Installing new showerhead rough-in (new studs, blocking, supply piping) - Adding body spray system (new supply manifold) - Replacing tankless water heater (new installation) - Changing water heater fuel type (gas<->electric)
When no permit required: - Like-for-like showerhead replacement (same location, same connection) - Replacing handshower slide bar (no new piping) - Water heater in-kind replacement (same fuel, same BTU +/-10%)
Water Heater Code — FL Specifics
FPC Chapter 5 — Water Heaters: - Tankless units require dedicated gas or electrical circuit - Gas tankless: minimum 200,000 BTU installations need 1-inch gas supply in most FL applications - Temperature relief valve required on all tankless units (ASME rated) - FL Energy Code (FECC) requires EF >= 0.67 for gas storage; tankless typically EF 0.82–0.96 - South FL HVHZ: all outdoor tankless enclosures must meet Miami-Dade NOA 140 mph wind rating - FL Statute 163.04 prohibits HOAs from preventing installation of solar water heaters
SWFRPC Overlay (Lee, Collier, Charlotte, Sarasota): - SFWMD requires WaterSense-labeled showerheads on all new construction (per SFWMD Rule 40E-22) - Rebate programs available through SFWMD and utility partners
Installation Checklist
- Showerheads <=2.0 GPM each at 80 psi (FPC 604.4) — or WaterSense <=1.8 GPM for SFWMD rebate
- Body sprays <=0.5 GPM each (FPC 604.4.2) — each outlet individually rated
- Individual shutoff valves for each shower outlet — required if aggregate flow >2.0 GPM
- Pressure balancing or thermostatic valve installed (FPC 424.3) — required in all shower applications
- Shower drain properly sized for peak GPM (FPC Table 709.1)
- Hot water supply sized >=3/4" for systems >4 GPM (FPC Table 604.4)
- Tankless heater permit pulled if new installation (FBC Section 105)
- Gas line sized for total BTU demand if gas tankless (NFPA 54 / FPC 411)
- Relief valve and condensate drain piped correctly (FPC 504)
- Accessible cleanout for tile shower drain (FPC 708.3 — within 5 feet of shower)