What the Florida Building Code requires for an AC condensate drain line

Which part of the Florida code covers the drain line

The Florida Building Code (FBC) is the state's building rulebook. The City of Tampa says it draws upon national model building codes and national consensus standards, which are amended where necessary for Florida's specific needs. Tampa also says the Florida Building Commission adopts a new edition every three years.

Two volumes matter here. One is the Florida Building Code, Mechanical, and its Section 307 is titled Condensate Disposal. The Florida Building Code, Residential, has its own condensate section, numbered M1411.3.

The edition is changing. The 8th Edition (2023) Florida Building Code, Mechanical is the base for the 9th Edition (2026), according to the Commission. Miami-Dade County says the 9th Edition becomes effective on December 31, 2026. The City of Tampa's notice says January 1, 2027. Tampa says that to qualify for vesting under the 8th Edition, building plans must be submitted and the permit application accepted by December 31, 2026. Ask your own building department which date it uses.

One limit, stated plainly: the official online copy of the Florida code refused our requests. We quote it below through Florida government documents that reprint its wording.

Where the water is allowed to go

Section M1411.3 of the residential code, as reprinted in a Pinellas County amendment filing, says condensate shall be conveyed from the drain pan outlet to an approved place of disposal. The same filing's text says condensate shall not discharge into a street, alley or other areas where it would cause a nuisance.

Miami-Dade County lists Section 307.2.1.1 among the 8th Edition's significant changes. Miami-Dade County reprints it. It says condensate drains shall not directly connect to any plumbing drain, waste or vent pipe. The International Code Council (ICC), writing about the same rule in the 2021 International Mechanical Code, says health hazards are created by drilling holes in plumbing vent piping in attics to connect a condensate drain.

The section lists the only plumbing fixtures that may receive condensate. They are a floor sink, floor drain, trench drain, mop sink, hub drain, standpipe, utility sink or laundry sink. A connection to a bathroom sink's drain fitting, called a lavatory wye branch tailpiece, or to a bathtub overflow pipe is not treated as draining into a fixture. Writing about the 2021 International Mechanical Code, the ICC says this text clarifies that those connections are acceptable, as this has been a common practice in some localities.

Except where the line discharges to grade outdoors, its point of discharge must be within the same occupancy, tenant space or dwelling unit as the source of the condensate.

Local rules can be stricter. Miami-Dade County says its Water and Sewer Department's ordinance 8-CC prohibits any unmetered water from air conditioners from entering the sewer system. So the fixture option is not allowed there.

Pipe size, pipe type and slope

A Florida Building Commission report on proposed modification M11775 for the 2026 code update gives this text for Section 307.2.2 of the mechanical code, on drain pipe materials and sizes. It allows a list of plastic and metal pipe, including PVC, copper and galvanized steel. It says components shall be selected for the pressure and temperature rating of the installation.

That text says the drain line size shall be not less than 3/4-inch pipe size and shall not decrease in size from the drain pan connection to the place of condensate disposal.

The Pinellas County filing's text for Section M1411.3 calls for a downhill slope of not less than one-eighth unit of drop for every 12 units of run. The U.S. Department of Energy (DOE), describing the International Residential Code, says the code allows for 1/8-inch per foot. It adds that manufacturers often recommend a drop of a quarter inch per foot.

Backup protection when an overflow could cause damage

A clogged drain line can back water up into the pan. For that reason the model codes call for a second line of defense in some places. We could not get the official text of Florida's own section on this, so this part uses national sources.

The DOE's Building America Solution Center says the International Residential Code (IRC) requires that evaporator coils have a secondary drain pan if blockage of the drain pipe and overflow of the primary drain pan would cause damage to building components. The DOE adds that the second pan should discharge to a conspicuous spot, meaning somewhere you will notice the water.

An ICC guide, describing the International Fuel Gas Code's rule for appliances in attics and upper stories where leakage would cause damage, lists the main ways this is done. The most common is an auxiliary drain pan, meaning a second pan, under the unit. Another is a separate three-quarter-inch drain line from the unit's own pan, ending in a place people will see. A third is a device that shuts the system off automatically when the drain stops up.

The ICC guide's drawing shows the auxiliary pan at a minimum depth of 1.5 inches. The DOE calls the shutoff device a water-level detection device, also called a float switch. The DOE also says no trap should be installed on the auxiliary pan drain pipe.

Florida's 8th Edition added a labeling rule in Section 307.1.1. Miami-Dade County describes it as applying to condensate piping from fuel-burning appliances. Where that hidden piping ends, it must be marked to show whether it comes from the primary or the secondary drain.

Insulation: the 2026 change and a Pinellas County amendment

A proposal (modification M11775) filed for the 2026 Florida code update addressed uninsulated condensate piping. It said moisture in unconditioned spaces condenses on the outside of the pipe and can drip onto walls and ceilings. The proposal said that drip can cause water damage and support the growth of mold.

The Commission's summary of the 9th Edition says new language was added to Section 307.2.2. It requires drain pipes carrying condensate from cooling coils and evaporators to be insulated to at least R-3 inside a building's unconditioned space.

Pinellas County's licensing board filed a local amendment to the 8th Edition's Section M1411.3. It would require all primary condensate drain lines in unconditioned areas to be insulated to at least R-3. A Florida Building Commission action chart records a motion to deny a Pinellas County amendment on drain line insulation, 8 yes and 0 no. If you live in Pinellas County, ask the building department how it treats drain line insulation today.

For where indoor units sit and why attic units raise the stakes, see where an air handler can go.

What this means for a homeowner

The code describes how a drain line must be built. Changes to the drain piping, a new pan or a float switch are installation work. Fitting a float switch is electrical work for a licensed contractor.

You can still use the code to ask good questions. Ask where your drain line ends and whether that spot is an approved place. Ask whether your unit has a second pan, a second drain line or a shutoff switch. Ask which code edition your permit falls under, and whether the drain line in your attic is insulated.

If water is already showing up, start with why an air conditioner leaks water and how AC drain pans work. For how permits work, see HVAC permits in Florida. HVAC stands for heating, ventilation and air conditioning.