It is an unfortunate reality that many people underestimate the potential damage water can cause with even limited exposure time. Chemistry teaches that water can be a base or an acid depending on environmental factors meaning that in high acid environments, water acts as a base and in low pH environments, water is slightly acidic. The mutable nature of water affords water the ability to carve through solid rock to create beautiful natural wonders but this same ability can also destroy drywall, plumbing materials, and other common building materials. This point, however, is often forgotten when people deal with water damage.
When dealing with water damage, many people simply focus on the top layer of water and neglect to do anything for the layers of water that have penetrated the subsurface or been absorbed in to the gypsum board (aka drywall and sheetrock) and sill plates usually due to the double whammy of they do not understand the risks and they do not have the proper extraction equipment. Wikipedia reports that gypsum board is "easily damaged by exposure to water" and "supports the growth of mold." While gypsum board is treated to make it more water resistant, should the gypsum board be punctured or should water, as in the case of water damage, collect around the unprotected area of the gypsum board, the porous gypsum board will then readily absorb and hold the water. The longer this absorbed water stays inside the gypsum board the more damage it causes.
Unlike fire damage that leaves a visible and generally static path of damage, water damage can be subtle and can manifest its destruction over a period of time. Opposed to the immediate destruction caused by fire, water, similar in many ways to stress, can slowly chip away at the host until it requires extensive repair at a cost that is MUCH higher and over an area MUCH larger than initial exposure would have been required to treat. The subtle nature of water is what causes water damage to be regularly underestimated and, therefore, undertreated in real world case scenarios.
Unfortunately, despite the best intention and valiant effort of many honorable do-it-yourselfers, their efforts are for naught as they simply lack the equipment needed for remediation and such equipment is not commonly available at your local rental shop. At best these people may have access to a commercial carpet cleaner which can effectively remove the top layer of water but does little to penetrate the subflooring or remove the absorbed water so they will stop when the area feels dry and will leave a fan on. This method is very similar to the method employed by remediation professionals in the infancy of the water restoration profession but this was soon sent to pasture as it was quickly shown to be ineffective, at best, and a catalyst for decomposition and mold growth, at worst.
The best way to combat water damage, and to prevent the short and long term devastation caused by water damage, is to call a professional water damage restoration company as soon as the damage is found. While the honorable do-it-yourselfer will have the unrelenting urge to break out their equipment and assist the professional water damage restoration company, the best way a do-it-yourselfer could assist the company is by disabling the source of the water damage (if possible), ensuring the area is free from electrical risks, and ensuring the affected area is free of debris and physical hazards (if possible) so that the professionals can extract the water as quickly as possible to minimize the restoration time.
Proper timing is essential for the fastest restoration. Now you know.