Truth About Reoccurring Spots
Many people believe spots come back. Sometimes they do, but sometimes they are just new spots that appear in high traffic or common areas. The reason a spot may come back is because the volume of the spill was great enough to get past the carpet and into the pad below. When I come and clean a carpet I can only add so much soap and water because I risk causing a greater issue like over saturation. Over saturation can lead to very long drying times which can lead to the possibility of mold growing. So, since the spill still remains in the pad, it can seep back up to the surface as the carpet dries, or simply when you walk on it over a period of time.
A pro-tip for all problems mentioned above would be to purchase a wet/dry shop vacuum. Getting spills up as soon as they happen can dramatically decrease the risk of the spill getting into the pad and staining.