Water leaks happen. And when they do, it is best to take care of them right away to prevent mildew, mold and rotting.
Once you have taken care of that leak, you may be left with unsightly water stains on your walls or ceilings. These stains are ugly and an ugly reminder of that leak that probably cost you a pretty penny to fix.
Unfortunately, simply painting over the stain with regular latex paint will not do the job. Fortunately, there are only a few more steps you need to take.
1. Scrape Away Loose Material
If the leak was bad or recurring, it is likely that there is loose material and peeling paint. Do not just paint over that. Take a putty knife and scrape it away. Do not push too hard; use just enough pressure so that the already flaking flakes flake off. You can then use a rag and just wipe away smaller pieces.
Note: if the leak was bad, make sure the drywall and the studs are not waterlogged or damaged. You will be able to tell this if your drywall is soggy or severely damaged. If there is damage, fix this first. Locking in moisture and mold will come back to haunt you for sure.
2. Disinfect The Area With Bleach
The water likely caused mildew, mold, or bacteria, so use diluted bleach to kill these before applying primer. A good bleach: water dilution ratio is 1:3. This will also help fade the stain a bit.
Now is NOT the time to paint. Now is the time to dry. Do not paint over a wet spot.
3. Apply A Stain Concealing Primer
Use a primer before you use your latex paint. We recommend a primer that is designed to cover stains and also kill mildew and mold. Killz is a great brand, as is BIN. These are heavy-duty and will get the job done.
Be sure to spread the primer evenly and within a few inches each direction. Allow the primer to dry before adding the second coat.
Paint only after the primer has dried. Notice the theme here: dryness!
You may notice, depending on how long it has been since you last painted the wall/ceiling, the paint in the can and paint that is years old and on your walls are not the same color. This is because dust and sun and time have changed the color on your walls.
If possible, use the same application tool you used for the original paint job as this will increase the likelihood of the new paint blending in better. However, keep in mind there is a chance you will see a slight difference in the newly painted spot even if you used the same can of paint.
If your paint is old and you notice that it has thickened and may not match the wall color anymore, you can add paint reducer. This often happens to latex paint if it has not had an airtight seal or has been exposed to severe temperatures.
Before adding paint reducer, before sure to check that you really need it as adding it to paint that does not need it will make that paint too thin and equally as hard to work with. To test, dip your paintbrush in and let the paint drizzle off. If it drizzles evenly like heavy cream, it is good paint and needs no additives.
You do not need to buy actual paint reducer. You can use water.
Take the remaining paint from the can and dump it into a 5-gallon bucket. Pour about ½ cup(if 1/2cup seems like too much, just start with less) of room temperature water into the bucket and stir until there is an even consistency. Check the paint again to see if it drizzles off the stick nicely. If not, add more water, about an ounce at a time.
Obviously, it is better to start with less water than more!
Keep in mind through this process that there is a good chance you will see a difference between the patched spot and the rest of the wall. Depending on the light and time of day, it may be more noticeable.
But rest assured, if you have used the same color paint, your guests will not notice.