Spills, snow and water tracked in, rain through an open window, pipes bursting, leaky radiators, floods and even overwetting by do-it-yourself carpet cleaners can wet out the backing yarns of carpeting.
Followed by slow drying, this wetting will allow dye-like materials to dissolve out of the backing yarns and "wick" to the face of the carpeting. The brown discoloration which forms is usually referred to as a water stain.
After a water stain has developed, it may be impossible for even a professional cleaner to remove it. Gradual and uniform soiling on the face yarns may cause the stain to go unnoticed until the carpeting is thoroughly cleaned. Once the dirt is removed, the dye-like water stain becomes quite apparent.
Water is essential to professional cleaning of carpets and rugs; however, we know the proper amount and the conditions under which water can be used on carpets and rugs. For example, in a modern rug cleaning plant where controlled drying temperatures are possible, it is a safe and normal procedure to use hundreds of gallons of water on a single rug.