AC Leaking Water? How a Clogged Drain Line Causes It in a Florida Home

Why your AC makes water in the first place

Your air conditioner doesn't just cool the air. It also pulls moisture out of it. In humid Space Coast weather, that moisture collects on the cold indoor coil, drips into a pan, and flows out through a drain line, usually a white PVC pipe that ends outside or at a nearby drain.

That's normal. A leak means the water isn't getting out the way it should. ENERGY STAR warns that "a plugged drain can cause water damage in the house and affect indoor humidity levels" (ENERGY STAR Maintenance Checklist). The U.S. Department of Energy (DOE) lists drainage problems among common AC problems and says to "check your unit's drain to make sure it isn't clogged" (DOE Energy Saver 101: Home Cooling).

Common causes of an AC water leak

• A clogged condensate drain line. Algae, slime, dust and debris build up inside the line over time, and our warm, damp climate helps that growth along. Once the line clogs, the pan fills and overflows.
• A full or rusted drain pan. Older metal pans can corrode and leak even when the line is clear.
• A disconnected or cracked drain line, sometimes after other work in the attic or closet.
• A frozen coil that's melting. When ice thaws, it can produce more water than the pan handles. See Why Is My AC Frozen?

Signs your drain line is clogged

• Water in the pan under the air handler, or water on the floor of the AC closet or garage
• Water stains on a ceiling under an attic unit
• The AC shut off and won't turn back on (often a float switch doing its job)
• Water dripping from a pipe over a window, door or soffit outside. On many attic installs that's the secondary (backup) drain, and it usually means the main drain line is clogged. Call to have it cleared, even if the AC still cools.
• A musty smell near the unit, or the house feeling more humid than usual

Why the AC might shut itself off

Florida's mechanical code requires a backup where an overflow could damage the building. Depending on the setup, that's an extra drain pan with its own drain, a secondary overflow line, or a water-level switch that "will shut off the equipment served in the event that the primary drain is blocked" (Florida Building Code, Mechanical 2023, Section 307.2.3).

So if your system stopped cooling and there's water in the pan, the switch probably did exactly what it's meant to do. Don't bypass it. The fix is clearing the drain, not defeating the safety device.

What to do right now

1. Turn the system to Off at the thermostat so it stops making more water.
2. Keep water away from electrical. If water is near outlets, the unit's wiring or your electrical panel, leave everything off and call.
3. Contain the water. Towels, a shallow pan or a wet vac can keep it from spreading.
4. Check the filter. If it's dirty, replace it with the size printed on the old filter's frame.
5. Look for ice. If you see ice on the coil or copper lines, follow our frozen AC steps first.
6. Call if it doesn't clear. A technician can clear the line, check the pan and switch, and find out why it clogged.

Don't:

• Open the air handler cabinet or electrical panels.
• Bypass or unplug a float switch or water-level switch.
• Run the system while water is overflowing.
• Pour harsh chemicals into the line. A homeowner-safe option is about a cup of plain white vinegar poured into the drain's access port (the capped T near the indoor unit), monthly during cooling season. Don't use bleach, drain cleaners or other harsh chemicals, and never mix chemicals. Don't use a pressure washer or compressed air in the line. If the line is already backed up or water is overflowing, turn the system off and call us.

Not sure what you're seeing? Ask Mikey. Mikey walks you through safe checks, and hands you to a real person when it's time.

Attic, closet and condo units

• Attic units can leak into the ceiling below before anyone notices. Check the area under the unit when you change filters, and watch for ceiling stains.
• Closet and garage units usually show water on the floor first.
• Condos can send water into a neighbor's unit below. Check your condo documents for who's responsible for the drain and equipment. See Condo AC Replacement for more on HOA rules and access.

How to keep it from happening again

• Keep the drain flowing. Our Space Coast AC Maintenance Checklist covers the monthly drain step in cooling season. DOE also suggests occasionally passing a stiff wire through the unit's drain channels to prevent clogs (DOE Energy Saver 101).
• Check the filter monthly and replace it every 1 to 3 months.
• Get regular professional maintenance. ENERGY STAR's checklist includes inspecting the condensate drain (ENERGY STAR). See our HVAC maintenance service.

If your pan is rusted or the system keeps having problems, it may be time to weigh the bigger picture. See Repair or Replace Your AC in Brevard County?

The next step

A leaking AC is usually a simple fix if you catch it early. We clear the drain, check the pan and safety switch, find the cause, and quote any repair in writing. We serve homes across Brevard County, including Melbourne, Palm Bay, Titusville, Cocoa, Merritt Island and Viera.

• Start My Estimate
• Ask Mikey (Mikey is free)
• Call (321) 405-1806

Firefighters, law enforcement, EMS and paramedics, healthcare workers, teachers, ministry, government employees and military (active and veterans) can get 10% off the total, up to $2,500, on new units and repairs through our Local Heroes program. Family members of eligible heroes qualify too. It can't be combined with other offers.

Frequently asked questions

Sources

1. ENERGY STAR Maintenance Checklist
2. DOE Energy Saver 101: Home Cooling
3. Florida Building Code, Mechanical 2023, Section 307.2.3

Written by Cooling 321, Space Coast, Brevard County, FL. State Certified Air Conditioning Contractor, License No. CAC1825377. General information only; your system and home are reviewed before any recommendation.