Some spills don't just stain your carpet--they actually stain the pad beneath it. This may not be a problem if it was something harmless, such as juice, but if it has an unpleasant odor you may find that the smell will simply not go away. Virtually all consumer carpet cleaners will not clean a carpet pad, and trying to saturate the carpet pad will actually only lead to mildew:
Pull Up Your Carpeting
This is the scariest part, but it's actually fairly harmless. If your carpeting was installed more than a month or so ago, it's already stretched. You don't need to worry about stretching it again. What this means is that you can pull the carpeting up from the nearest corner and then place it back down without any specialized tools. Begin by locating the closest edge of the carpet and carefully pulling it up. There will be tacks under the carpet so be careful! They're sharp.
Clean Up the Stain
You should be able to see where the stain is on the back of the carpeting as well as the pad. Use a cleaner (enzyme based cleaners are best for stains like pet urine) to wet down the stain thoroughly on both sides. Blot the stain with a dry cloth and repeat the process until the stain has come up. Allow the area to dry completely before moving forward. You may also want to use an odor remover at this time.
Replace the Padding
If the padding stain will not dissipate, you can simply pull up the padding and bring it to your local carpet store. They will be able to identify it so that you can replace the padding; there are only so many types of padding out there and most of them are very similar. Padding doesn't need to be glued or nailed down, it's just rolled out flat on the ground beneath the carpet.
Put the Carpet Back
Putting the carpet back should be fairly simple. Slowly roll the carpet back down and then gently push it down on the tacks at the edges. Once it has been secured, you will need to tuck the edges of the carpet under the baseboard. If you see any lumps or ridges, simply pull the carpet up and then repeat the process, taking care to pull on the carpet as you go.
If you still can't get rid of the stain--or your carpet still has an odor--it's best to call a professional carpet cleaning before you try anything else. Harsh cleaners and scrubbing may damage the carpet further. To learn more, contact a company like H & L Janitorial Service with any questions or concerns you have.