my brother spilled water on the carpet and instead of drying it up he just threw a towel over it and left it all night. now the carpet smells really bad of mildew. i tried washing it with soap and water and it helped a little. i tried febreeze but that did no good. i don't have a steam carpet cleaner.
The carpet just sat overnight and now smells of mildew? Wow. First you need to kill the mildew. I would spray it with Lysol so that you saturate the wet spot. You need to make sure that the padding underneath the carpet will be clean and dry, so you may even need to lift up the carpet to check the padding. If the water has saturated through to the padding, you need to Lysol that too. Then blot it with a towel to get as much of the moisture out as possible, and turn a fan on that spot and leave it for a couple of days until you are sure it is completely dry. Then work some baking soda into the carpet and vacuum it up.
