If you have a carpet pad that has a moisture barrier, you might think that you're ready for any sort of water exposure. Moisture barriers and waterproofing are great features to have normally because they help prevent ground moisture from seeping up into the carpet and home, and they protect the base floor from moisture exposure from spills.
But a flood is a lot different than spilling some water. Even a short flood, like a burst pipe, exposes the pad to much more water than a spill, and for a longer time.
If there is a flood of any type that soaks the pad -- or even if you think it might have just reached the pad, much less soaked it -- you need to have the carpet and pad removed and dried out. The floor underneath will also need inspection and possibly restoration help, even if the floor is made of concrete.
How Those Barriers Are Meant to Work
Moisture barriers are supposed to prevent ground moisture from seeping up into the pad and carpet, and to prevent water (or other liquids, as pet owners will tell you) from seeping through the pad to the floor below. If something drips on the carpet, it's stopped by the barrier. You may have a stained carpet, but the pad and floor will be fine.
But for floods, when you have a lot of water just sitting there for hours or days, the barrier means nothing. Water finds a way to move.
What That Water Can Do
If water gets under the pad and isn't extracted, and the area not dried out, that water can't evaporate away if there's a moisture barrier.
The effects can be almost immediate. The barrier might not hold up, letting water soak the base floor. And the water in the room could seep down around the edges of the carpet and pad, bypassing the barrier and pad altogether.
Longer-term effects include more mildew, mold, and rot, if the floor underneath is made of wood. You risk having the floor fail later on from all the rot in addition to all the health problems that come with living in a moldy house. Even concrete isn't safe; it's porous, so water can seep in, and if it can't evaporate, then you'll have continued mildew problems on the underside of the pad.
This is something that can happen even if you replace the carpet. If you don't remove the pad and extract water from all levels of that floor (carpet, pad, and base floor), you are leaving a rotting problem there that could haunt you later.
How to Handle a Flooded Carpet
Once the flood has receded and you can see the carpet again, you need to call a restoration company that specializes in water damage. Floodmasters is one such company and can quickly evaluate what needs to be done to save not only your floor, but also anything else in the house that was exposed to the flood.
Chances are the carpet and pad may need to be removed; the base flooring will need time to dry as well. Restoration companies have industrial fans and dryers that they'll set to work as soon as possible. If the carpet and pad turn out to be in decent shape, it might be possible for the company to save those. But in most floods that involve days of water exposure, you should plan on replacing the carpet and pad.
Restoration companies will inspect for water damage and discuss your options with you, so you know exactly what steps to take next. Don't assume air drying is all your carpeted floor needs. Get a restoration company to work on all layers and make your home safe to live in again.