Should You Run Your AC After Water Damage?

Quick answer: Usually yes, if the HVAC equipment and ducts stayed dry. In Central Texas the AC is one of your best tools for pulling moisture out of the house while things dry, as long as indoor humidity ends up below 60%. Don’t run it if water reached the air handler, ducts or wiring, or if you suspect mold in the system, until a professional checks it, as the EPA advises.

Why does running the AC help dry a house after a leak?

The AC helps because cooling and drying happen at the same coil. As warm indoor air crosses the cold evaporator coil (the indoor coil in the air handler), moisture condenses and runs down the drain. Wet drywall and carpet keep releasing water into the air, and the AC keeps hauling it away. Open windows in a Central Texas summer do the opposite, since outdoor air is often wetter than what you’re trying to dry.

Set the fan to Auto, not On. A fan that runs nonstop blows across the wet coil between cycles and puts that water right back into the house.

When should you not turn the AC on after water damage?

Leave it off if water touched the system itself or the water was dirty. Specifically:

• Water reached the air handler or furnace, such as a closet or garage unit that sat in water or an attic unit under a roof leak.
• Ducts or return grilles sit in the wet area, like a floor register or low return in a flooded room.
• The water came from a sewer backup or outdoor flooding.
• Vents smell musty or you can see growth near the return.
• Any electrical part of the system got wet. Leave the breaker off until it’s checked.

The EPA’s flood guidance is to have an HVAC system that got wet checked and cleaned by a professional before you use it. If that’s your situation, Gold Eagle can check the air handler, ducts and wiring and tell you what needs cleaning or repair before you turn it back on; schedule a visit online or call 512-489-4653.

Can running the AC spread mold?

Yes, if the mold is inside the system or the return pulls air from an area with mold growth. The EPA advises against running an HVAC system you know or suspect is contaminated. During a mold remediation project, the work area is usually sealed off and its registers covered so the system doesn’t carry anything from that room to the rest of the house. Mold in the walls, flooring or belongings is a job for a general mold remediation company, while mold in the AC system or ductwork is HVAC mold that a licensed HVAC mold remediation company like Gold Eagle handles.

Is the AC enough, or do you need dehumidifiers and fans?

For a small leak caught early, the AC plus a couple of fans is often enough. Bigger losses need dedicated dehumidifiers and air movers, because the AC removes moisture only while it’s cooling. On a mild March day it may barely run, and humidity creeps up. An oversized system short-cycles and removes less water than you’d expect; why a bigger AC isn’t better explains why.

A simple hygrometer, or the humidity reading on your thermostat, tells you whether it’s working. Aim for below 60%, ideally 30% to 50%, per the EPA.

What should you check on the AC once everything is dry?

• Swap the filter, because drying and demolition fill the air with dust.
• Make sure the condensate drain is flowing after all that extra water.
• Sniff for a musty smell when the system starts.
• Have the coil and drain pan looked at if the leak was near the equipment.

Can your HVAC system grow mold? covers how to keep the system itself clean going forward, and how indoor moisture affects your home’s air covers the humidity side.

What should you do next?

• If any part of the system got wet, leave the breaker off and have it checked before you use it.
• If the equipment and ducts stayed dry, run the AC with the fan set to Auto.
• Watch a hygrometer or your thermostat’s humidity reading and aim for below 60%.
• Once everything is dry, swap the filter, and book a Gold Eagle visit if the leak was near the equipment.

Related guides: How Indoor Moisture Affects Your Home’s Air, Can Your HVAC System Grow Mold? How to Prevent It and Why a Bigger AC Isn’t Better in Texas Heat.

About Gold Eagle Services: This guide comes from the team at Gold Eagle Services, a family-run Austin HVAC, indoor air quality and mold remediation company founded in 2017. We’re licensed (TACLA119235 and RCO1783), insured and bonded, and we serve homes across the greater Austin area.

Need help with this in your home? Learn about our humidity control and indoor air quality solutions, or call 512-489-4653 to schedule a visit.

Related Gold Eagle service: HVAC mold remediation