Mold After a Water Leak: What to Do in the First 48 Hours
A supply line under the sink lets go. The AC drain backs up and a brown ring appears on the ceiling. The water heater starts weeping in the closet. Whatever the source, the question most people search next is the same: how long until mold starts growing?
The EPA's answer is the one to plan around. If wet or damp materials are dried within 24 to 48 hours after a leak, in most cases mold will not grow. After that, the odds shift. In south Louisiana, where indoor air is often humid to begin with, things don't dry out on their own as quickly as you might hope.
Here's a practical order of operations.
Step 1: Stop the water and make it safe
- Shut off the water. Use the fixture's shutoff valve or the main valve to the house.
- AC leak? Turn the system off at the thermostat so the unit stops producing condensate while you sort out the drain.
- Watch for electricity. If water is near outlets, fixtures, or a sagging ceiling, turn off power to that area at the breaker. A ceiling that's bulging with water can come down. Keep people out from under it.
- Roof leak? Put containers under drips and, once the weather allows, get the roof temporarily covered.
Step 2: Document before you move things
Take photos and video of the water, the source, and anything damaged before you start cleaning. Note the date and time you found it. If you end up filing an insurance claim, this record matters, and it's hard to recreate later.
Step 3: Get the water out and start drying
- Mop or wet-vac standing water.
- Pull wet rugs, cushions, and boxes out of the area.
- Run fans and a dehumidifier, and keep the AC running if it's working and not the source of the leak. The CDC recommends keeping indoor humidity no higher than 50 percent, and an air conditioner or dehumidifier helps.
- Open cabinet doors under a leaking sink so the cabinet base can dry.
Step 4: Decide what can be saved
The EPA's rule of thumb: hard, non-porous surfaces can be cleaned with detergent and water and dried. Porous materials that got soaked, such as carpet pad, ceiling tiles, and insulation, may have to be thrown away, because mold can grow into them and be hard or impossible to remove completely.
Drywall is the tricky one. The surface can feel dry while the back side and the insulation behind it stay wet. That's why a leak that "dried up" can turn into a musty wall a few weeks later.
Where hidden water goes in Lafayette homes
Water follows gravity and framing, and the way homes here are built affects where it ends up:
- Raised homes: A leak under a bathroom or kitchen can run straight through the subfloor into the crawl space, where it soaks joists and insulation you never see. If your home is on piers, check underneath after any significant leak. Our guide to crawl space mold removal covers what to look for.
- Attic air handlers: Many Acadiana homes have the AC unit in the attic. A clogged condensate line or cracked drain pan can soak attic insulation and ceiling drywall long before the stain shows below. The EPA recommends keeping drip pans clean and drain lines flowing. See attic mold remediation if you're already finding growth up there.
- Slab homes: Water from a supply line or water heater can wick under baseboards, into the bottom of walls, and under flooring.
The EPA also lists common spots for hidden mold: the back side of drywall and paneling, the underside of carpet and pad, inside walls around leaking pipes, and inside ductwork. If you smell mold but can't see it, that's where to suspect it.
A note about the AC
If the leak involved the HVAC system or there's mold near the air handler or return, be careful. The EPA advises not running an HVAC system you know or suspect is contaminated with mold, because it can spread spores through the house. Get it checked before running it again.
Can you clean it up yourself?
Sometimes. The EPA says that if the moldy area is less than about 10 square feet, roughly a 3-foot-by-3-foot patch, most homeowners can handle it themselves using the right protection: gloves, goggles, and an N-95 respirator. Scrub hard surfaces with detergent and water, and dry them completely. Don't paint or caulk over mold.
Call a professional when:
- The water soaked a large area, or mold covers more than about 10 square feet
- Water got inside walls, under flooring, into the crawl space, or into attic insulation
- The water came from a sewage line or toilet overflow (the EPA recommends a professional experienced with contaminated water)
- The HVAC system may be involved
- You can't find the source of a musty smell
What affects the cost of drying and cleanup is mostly how far the water spread, how long it sat, what materials got wet, and whether anything has to be removed. The faster drying starts, the smaller the job usually is.
Get help drying it out
If water is still in the house or soaked into the structure, start with water damage restoration so everything is dried properly before mold has a chance to set in.
One call connects you with a local pro. Call (337) 205-7937 to describe what happened and get a free, no-pressure quote.
Frequently asked questions
How long does it take mold to grow after a leak?
The EPA says that drying wet materials within 24 to 48 hours will prevent mold growth in most cases. Beyond that window, assume materials that are still wet could start growing mold.
Can mold keep growing after the leak is fixed?
Yes, if materials are still wet. Fixing the leak stops new water, but drywall, insulation, and wood can hold moisture for a long time. They have to be dried or removed.
Should I use bleach on mold after a leak?
The EPA doesn't recommend biocides like bleach as routine practice. Scrubbing with detergent and water, then drying, works for hard surfaces. Never mix bleach with ammonia or other cleaners.
Does homeowners insurance cover mold after a leak?
Policies often treat mold from a sudden event, like a burst pipe, differently from mold caused by a slow leak over time. Photos and prompt action help. Check your policy; your insurer decides what's covered.
Lafayette Mold Pros connects homeowners with independent local mold remediation professionals.