Except for those who wish to celebrate Lumpy Rug Day on May 3rd each year, rugs that refuse to flatten can be both annoying and a fall hazard. Rugs take large amounts of wear and tear --- from foot traffic, settling floors, pets, spills and environmental exposures such as sun and humidity. Lumps, creases and bumps can occur over time, and sometimes are found in new rugs that were improperly rolled or folded during shipping. Although it may take more than one attempt, there are various ways you can flatten a rug.
Look under the rug to make sure nothing has fallen beneath it, causing the lump. Remove any small toys or items that may be pushing up the rug fabric.
Examine the floor to make sure there are no irregularities in the flooring that could be causing the lump in the rug. Older homes may have loosened floorboards or pushed-up tiles; if so, the flooring will need to be repaired before the rug can be laid back down.
Wash the rug in a washing machine, and either machine- or line-dry it. If it is too large for this process, vacuum the rug and shampoo it; this can usually be done with a steam cleaner or carpet shampooer. If the rug is very large, roll it up and take it to a nearby car wash; you can use the pressure hoses to clean the rug thoroughly, and bring it back home to line-dry outside. If necessary, have the carpet professionally cleaned at your home.
Mist the area of carpet with water from the spray bottle --- your goal is to dampen the material, but not saturate it. Lay something heavy on the wet carpet, such as a large bowl or a piece of furniture. Allow the heavy item to remain on the carpet overnight. As the rug dries, the weight of the item should press the lump flat.
Hang a large rug over a deck railing or bed, allowing the lumpy, creased area to hang free. You can spray it with water as well. The weight of the rug should straighten the fabric.
Iron a persistent lump with a steam iron, using the "wool" setting. Place a towel underneath the rug edge, if necessary, to keep the iron from touching the flooring. Press the carpet in the original direction of its pile for the best results.
Stretch the rug out tightly, making sure the lump in the carpet fabric has been pulled taut. Position a heavy piece of furniture at either end of the rug to hold it in place for at least 24 hours.
When flattening a dampened rug, do not use a book; ink from the jacket could stain the rug, or the moisture could ruin the book cover.