Untreated Water Leaks will Cause Mold
If you already know that you have had a water leak (such as leaking pipes or a leaking ceiling) then just that knowledge by itself, even if you don't see signs of water damage, is a good sign that you might have mold growing in your house around the area where the leak was. Untreated water damage can cause big threats to your home.
Mold growth from leaks can often be hidden. If the leak was behind a wall or other surface then any mold will probably be hidden behind the surface too. Even if the leak was not behind a surface there could still be mold hidden out of view behind a wall or other surface from water, which seeped through. It may be a week or two before it grows to the extent that it is visible to the naked eye as spots on drywall or carpet pads. Of course, mold being a living organism with its own agenda is not going to follow what is said in this blog thus there will be exceptions. Many times, a person will think that moisture was removed when in fact enough moisture was left behind to allow mold to start growing.
If a minor amount of moisture is lingering inside the wall cavities, behind the baseboards, in the carpet, or under the carpet padding it will likely be weeks before it all dries up, by that time the mold starts forming as visible sports on your walls.