The Short Answer
The supply line under the bathroom sink let go overnight. By morning the bottom of the hallway wall is dark, the baseboard is swollen, and the question is simple: how many days until this wall is dry?
You'll find day counts online. We haven't found a primary source that backs one for drywall, so this post doesn't give one. Here is what the sources do say.
- The target is 24-48 hours, not a forecast. The EPA's mold course says: "Dry items before mold grows, if possible. In most cases, mold will not grow if wet or damp items are dried within 24-48 hours."
- A flood is slower. The EPA's flood cleanup page says: "Drying can take a long time, usually several days to weeks." That page is written for floods, so read it as a warning, not as a schedule for your wall.
- Dry means dry inside. The same EPA page says not to apply paint or sealants "until you are sure the materials are completely dry on the inside."
So watch two things instead of the calendar: how fast drying started, and whether the readings are coming down.
What Changes the Answer for Your Wall
Two walls hit by the same leak can behave differently. These are the questions worth answering before anyone guesses at a timeline.
Where did the water come from?
A burst supply line and a sewer backup are not the same job. The EPA flood page notes that damage from a pipe leak or rainwater "typically presents fewer hazards" than flooding, and the CDC's disaster cleanup guidelines say: "Remove and discard drywall and insulation that has been contaminated with sewage or floodwater." If either of those reached the wall, skip ahead to when drywall should come out.
What is behind the board?
The face of the wall is only half of it. The CDC says mold "can also grow in dust, paints, wallpaper, insulation, drywall, carpet, fabric, and upholstery", and the EPA's brief guide to mold and moisture lists "the back side of dry wall" and "areas inside walls around pipes (with leaking or condensing pipes)" among the places hidden mold can sit. A leak inside the wall can wet the back of the board and the insulation, so the face can look fine while the inside is still wet.
How long did it sit before drying started?
This is the one you control. The EPA line doesn't say when the 24-48 hours start, so our practical advice is to count from when the wall got wet if you know it, not from when someone noticed. A slow leak behind a vanity may have been wetting the wall for weeks before the stain showed.
How is the room being dried?
A closed room with no air moving dries slowly. The EPA flood page says: "Open inside doors and cabinets, and remove drawers, shelves, and built-in furniture (such as cabinets) to allow hidden surfaces to dry. If you have power, you can set up fans, dehumidifiers, or heaters throughout the house to speed up the drying process."
What season is it?
Solano County summers are hot and dry and the winters are wet. A wall that gets wet in December can't lean on open windows the way a wall in July can, so plan on running fans and a dehumidifier rather than waiting for the weather to help.
How to Tell When a Wall Is Dry
Touch tells you about the paint. It doesn't tell you about the gypsum or the cavity behind it. Use these checks instead. None of them is a diagnosis. They tell you whether drying is working.
- Get a moisture meter. A basic one from a hardware store is enough to track a trend.
- Read a dry wall first. Take a reading on the same kind of drywall in a room the water never reached. That is your comparison point for this house.
- Read the same spots every day. Mark three or four points from the baseboard up to just above the stain line, and read them at the same time each day.
- Watch the trend, not one number. Readings that fall day by day toward your dry-wall reading are a good sign. Readings that stall, or climb, are a reason to get the wall looked at.
- Use your nose and eyes too. A damp smell that fades is a good sign. One that holds or turns musty, bubbling paint, or a baseboard that keeps swelling are reasons to find out what is behind the board. Our guide to what a wet drywall smell means goes through the smell side.
Before anyone patches, primes or paints, the EPA's line is the one to follow: "Do not seal any areas, such as wall cavities, that were flooded and do not apply paint or sealants to any surfaces that were wet until you are sure the materials are completely dry on the inside."
When Drywall Should Come Out
Drying in place is worth trying when the water was clean, drying started early and the readings are falling. These situations point the other way.
| Situation | What the source says | Source |
|---|---|---|
| Sewage or floodwater reached the wall | "Remove and discard drywall and insulation that has been contaminated with sewage or floodwater." | CDC, written for disasters and floods |
| Mold is growing on the wet board | "Porous materials that are wet and have mold growing on them may have to be discarded." | EPA, written for schools and commercial buildings |
| The material soaked up a lot of water and can't be cleaned and dried | "You should throw away materials that soak up a lot of water and can't be cleaned and dried." | EPA, flood cleanup |
| You suspect mold inside the wall | "If you believe that you may have a hidden mold problem, consider hiring an experienced professional." | EPA brief guide |
| The board is sagging, soft or crumbling, or readings won't come down | No source rule. Treat it as a reason to have the wall opened and checked. | Practical guidance |
The EPA remediation guide is written for schools and commercial buildings. We use it here as a fair yardstick for a house, not as a rule for homes.
Hold off on cutting test holes yourself if you think mold is involved. The EPA warns that investigating hidden mold "will require caution when the investigation involves disturbing potential sites of mold growth", and its example is that "removal of wallpaper can lead to a massive release of spores if there is mold growing on the underside of the paper."
For mold you can see, the EPA says: "If the moldy area is less than about 10 square feet (less than roughly a 3 ft. by 3 ft. patch), in most cases, you can handle the job yourself, follow the guidelines." Anything larger, or inside the wall, is worth a professional look. Mr. Fresh offers mold remediation, and our post on mold behind drywall after a slow leak covers that case.
Wall still wet after a few days?
Call or text (707) 816-7103 and tell us where the water came from and when it got in.
Drying It: The EPA's Steps and Practical Ones
If the water was clean and you caught it early, this is a sensible order. Steps that quote the EPA or Angi say so. The rest is practical guidance.
- Stop the water. Shut the supply valve, or the main if you can't find it. Drying a wall that is still being fed doesn't work.
- Photograph everything first. Angi's water damage guide advises: "Document damage with photos for insurance purposes before restoration begins."
- Get standing water up. Wet-vac the floor along the wall and pull back anything wet that is pressed against it.
- Open the hidden surfaces. Open cabinet doors and take out drawers and shelves so the EPA's "hidden surfaces" can dry.
- Clean visible mold before the fans go on. The EPA says "it's a good idea to wait to start up fans or dehumidifiers until after you've gently cleaned all the mold you can see at least once."
- Move air and pull moisture. The EPA says you can set up fans, dehumidifiers or heaters throughout the house to speed up the drying process. Point the fans across the wet wall.
- Keep the HVAC out of it if the water reached it. The EPA: "If any part of your HVAC system was affected by the flood, do not use it to help dry out your house."
- Take readings daily and don't paint until the wall is dry on the inside.
Some people should stay out of it. The EPA flood page says: "People with breathing problems like asthma or who have weakened immune systems should stay away from moldy sites and should not participate in flood cleanup." If that is you, or the wet area is large, call for help. Mr. Fresh runs emergency water extraction and water damage restoration across Fairfield and Solano County.
Cost and Insurance
These are Angi's 2026 national figures. They are not Mr. Fresh's price and they are not a quote. Angi's water damage page has no Fairfield or Solano County row.
| Item | National figure (Angi 2026) |
|---|---|
| Drywall (water damage cost breakdown) | $300 to $850 |
| Water damage restoration, whole job | $1,383 to $6,369, average $3,868 |
Source: Angi, water damage repair cost (updated September 11, 2026). National figures.
Whether a wet wall is covered is a question for your policy and your carrier. Angi's summary: "Homeowners insurance may cover water damage if it is sudden and accidental. However, damage that is gradual, such as from slow leaks, or results from a lack of maintenance, negligence, or general wear and tear is typically not covered."
Keep the photos, the date the water got in and your daily readings together. On a water job, Mr. Fresh documents the damage with photos and moisture readings and works with your adjuster.
Not Sure Your Wall Is Dry?
Mr. Fresh Carpet Care is a family-owned carpet cleaning and water damage restoration business in Fairfield, in business since 2013, with IICRC-certified technicians. We work across Fairfield, Vacaville, Suisun City and Benicia.
Call or text (707) 816-7103 with where the water came from, when it got in and what your readings are doing. Emergency dispatch runs 24/7. More on our services at mrfreshcarpetcare.com.
Frequently Asked Questions
How long does drywall take to dry after a leak?
We haven't found a primary source that puts a fixed number of days on drywall. In practice it depends on how much water got in, what is behind the board and how the room is being dried. The EPA gives a target rather than a schedule: in most cases, mold will not grow if wet or damp items are dried within 24-48 hours. Its flood cleanup page adds that drying can take a long time, usually several days to weeks, after a flood. Judge a wall by its moisture readings, not by the calendar.
Can wet drywall be saved?
Sometimes. A wall wet from a clean supply line, caught early, with readings that fall day by day, can be worth trying to dry. The CDC says to remove and discard drywall and insulation that has been contaminated with sewage or floodwater, so water from either of those is a different case. If mold is growing on wet drywall, the EPA's remediation guide, which is written for schools and commercial buildings, says porous materials that are wet and have mold growing on them may have to be discarded.
What moisture reading means drywall is dry?
There's no single number we can source for drywall in a home, and meters differ. A practical check is to compare the wet wall with a dry wall of the same drywall elsewhere in the house, and to watch the trend. Readings that fall each day are a good sign. Readings that stall are a reason to get the wall looked at.
Can I paint over drywall once it feels dry?
Not on touch alone. The EPA's flood cleanup guidance says not to apply paint or sealants to any surfaces that were wet until you are sure the materials are completely dry on the inside, and not to seal wall cavities that were flooded. The painted face can feel dry before the board behind it is.
Do fans and a dehumidifier help drywall dry?
The EPA says that if you have power, you can set up fans, dehumidifiers or heaters throughout the house to speed up the drying process. It also says it is a good idea to wait to start fans or dehumidifiers until you have gently cleaned all the mold you can see at least once, and not to use an HVAC system that the water reached.
Will wet drywall grow mold?
It can. The CDC lists drywall and insulation among the materials mold can grow in, and the EPA lists the back side of drywall and areas inside walls around leaking pipes among the places hidden mold can sit. The EPA's guidance is that in most cases, mold will not grow if wet items are dried within 24-48 hours, so it pays to start drying fast.
What does drywall water damage cost?
Angi's 2026 national figures list drywall as a $300 to $850 line in the cost breakdown for water damage repair, and put water damage restoration as a whole at an average of $3,868, with most homeowners paying between $1,383 and $6,369. These are national figures, not Mr. Fresh's price and not a quote.